Chapter 1 - Safety and Quality in the Hematology Laboratory
OBJECTIVES
An overview of the hematology laboratory
■ Explain the role of the hematology laboratory staff in providing quality patient care.
■ List five basic functions of the hematology laboratory. Safety in the hematology laboratory
■ Explain the basic techniques in the prevention of disease transmission.
■ Compare the features of general safety regulations governing the clinical laboratory, including components of the Occupational Safety and Health Administration (OSHA)-mandated plans for chemical hygiene and for occupational exposure to bloodborne pathogens, and the importance of the laboratory safety manual.
■ List and describe the basic aspects of infection control policies and practices, including how and when to use personal protective equipment or devices (e.g., gowns, gloves, goggles), and the reasons for using standard precautions.
■ Explain the purpose and correct procedure of handwashing.
■ Describe the contents of the laboratory procedures manual. Quality Assessment and quality control in the hematology laboratory
■ Summarize the essential nonanalytical factors in quality assessment.
■ Briefly describe computer-based control systems.
■ Define terms used in quality control and basic statistical terms.
■ Describe the basic terms and state the formulas for the standard deviation, coefficient of variation, and z score.
■ Describe the use of a Levey-Jennings quality control chart.
■ Compare three types of changes that can be observed in a quality control chart.
■ Explain the most frequent application of a histogram.
AN OVERVIEW OF THE HEMATOLOGY LABORATORY
Hematology, the discipline that studies the development and diseases of blood, is an essential medical science. In this field, the fundamental concepts of biology and chemistry are applied to the medical diagnosis and treatment of various disorders or diseases related to or manifested in the blood and bone marrow.
The Study of Hematology
Basic procedures performed in the hematology laboratory, such as the complete blood cell count (CBC), which includes the measurement and examination of red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes), and the erythrocyte sedimentation rate (ESR), frequently guide the primary care provider in establishing a patient’s differential diagnosis. Molecular diagnostics, flow cell cytometry, and digital imaging are modern techniques that have revolutionized the laboratory diagnosis and monitoring of many blood disorders, for example, acute leukemias and inherited blood disorders. The field of hematology encompasses the study of blood coagulation––hemostasis and thrombosis.
Functions of the Hematology Laboratory
Medical laboratory scientists, medical laboratory technicians, laboratory assistants, and phlebotomists employed in the haematology laboratory play a major role in patient care. The assays and examinations that are performed in the laboratory can do the following:
■ Establish a diagnosis or rule out a diagnosis
■ Confirm a physician’s clinical impression of a possible haematological disorder
■ Detect an unsuspected disorder
■ Monitor the effects of therapy
■ Detect minimal residual disease following therapy
■ Monitor the effects of therapy
■ Detect minimal residual disease following therapy
Although the CBC is the most frequently requested procedure, a laboratory professional must be familiar with the theory and practice of a wide variety of automated and manual tests performed in the laboratory to provide quality patient care. Continuing education is a necessity to keep up with continually changing knowledge and instrumentation in the field.
SAFETY IN THE HEMATOLOGY LABORATORY
The practice of safety should be uppermost in the mind of all persons working in a clinical hematology laboratory. Accidents do not just happen; they are caused by carelessness, lack of attention to detail, or lack of proper communication. Most laboratory accidents are preventable by exercising good technique, staying alert, and using common sense.
SAFETY IN THE HEMATOLOGY LABORATORY
The practice of safety should be uppermost in the mind of all persons working in a clinical hematology laboratory. Accidents do not just happen; they are caused by carelessness, lack of attention to detail, or lack of proper communication. Most laboratory accidents are preventable by exercising good technique, staying alert, and using common sense.
Safety standards for patients and clinical laboratories are initiated, governed, and reviewed by governmental agencies and professional organizations (see Box 1.1). The Joint Commission (www.jointcommission.org) has established National Patient Safety Goals. One of the goals of particular interest to laboratory professionals addresses the issue of critical laboratory assay values, the high and low boundaries of the life-threatening values of laboratory test results (see “Quality Assessment in the Hematology Laboratory”). Urgent clinician notification of critical results is the responsibility of the laboratory.
The Safety Officer
A designated safety officer is a critical part of a laboratory safety program. This individual has many duties affecting staff including compliance with existing regulations affecting the laboratory and staff, for example, labeling of chemicals and providing supplies for the proper handling and disposal of biohazardous materials.
BOX 1.1
Safety Agencies and Organizations
■ U.S. Department of Labor’s Occupational Safety and Health Administration (OSHA)
■ Clinical and Laboratory Standards Institute (CLSI)
■ CDC, part of the U.S. Department of Health and Human Services (DHHS), Public Health Service
■ College of American Pathologists (CAP)
■ The Joint Commission (The Joint Commission on Accreditation of Healthcare Organizations)
BOX 1.1
Safety Agencies and Organizations
■ U.S. Department of Labor’s Occupational Safety and Health Administration (OSHA)
■ Clinical and Laboratory Standards Institute (CLSI)
■ CDC, part of the U.S. Department of Health and Human Services (DHHS), Public Health Service
■ College of American Pathologists (CAP)
■ The Joint Commission (The Joint Commission on Accreditation of Healthcare Organizations)
Occupational Safety and Health Administration Acts and Standards
To ensure safe and healthful working conditions for workers, the US federal government created a system of safeguards and regulations under the Occupational Safety and Health Act of 1970. In 1988, the Act expanded the Hazard Communication Standard to apply to hospital staff. The programs deal with many aspects of safety and health protection and places responsibility for compliance on management and employees.
The Occupational Safety and Health Administration (OSHA) standards include provisions for warning labels or other appropriate forms of warning to alert all workers to potential hazards, suitable protective equipment, exposure control procedures, and implementation of training and education programs. The primary purpose of OSHA standards is to ensure safe and healthful working conditions for every US worker.
OSHA and the Centers for Disease Control and Prevention (CDC) have published numerous safety standards and regulations that are applicable to clinical laboratories (e.g., 1988 OSHA Hazard Communication Standard). Ensuring safety in the clinical laboratory includes the following measures:
■ A formal safety program
■ Specifically mandated plans (e.g., chemical hygiene, bloodborne pathogens)
■ Identification of various hazards (e.g., chemical, biological)
Chemical Hygiene Plan
In 1991, OSHA mandated that all clinical laboratories must implement a chemical hygiene plan (CHP) and an exposure control plan. As part of the CHP, a copy of the material safety data sheet (MSDS) must be readily accessible and available to all employees at all times. This document ensures that laboratory workers are fully aware of the hazards associated with chemicals in their workplaces. The MSDS describes hazards, safe handling, storage, and disposal of hazardous chemicals. The information is provided by chemical manufacturers and suppliers about each chemical and accompanies the shipment of each chemical.
On September 30, 2009, OSHA published the long-awaited Proposed Rule to modify the Hazard Communication Standard (HCS) to conform with the United Nations’ (UN’s) Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. OSHA has made a preliminary determination that the proposed modifications will improve the quality and consistency of information provided to employers and employees regarding chemical hazards and associated protective measures.
The proposed modifications to the chemical hazard communication (HAZCOM) standard include:
■ Revised criteria for classifi cation of chemical hazards
■ Revised labeling provisions that include requirements for use of standardized signal words, pictograms, hazard statements, and precautionary statements
■ A specifi ed format for safety data sheets (currently known as material safety data sheets)
■ Revised labeling provisions that include requirements for use of standardized signal words, pictograms, hazard statements, and precautionary statements
■ A specifi ed format for safety data sheets (currently known as material safety data sheets)
■ Related revisions to defi nitions of terms used in the standard and requirements for employee training on labels and safety data sheets
OSHA is also proposing to modify provisions of a number of other standards, including standards for flammable and combustible liquids, process safety management, and most substance-specific health standards, to ensure consistency with the modified HCS requirements. OSHA currently anticipates a 2-year phase-in period for new hazard communication training requirements and a 3-year phase-in period for overall implementation once the Final Rule is published.
“Right to Know” Laws
Legislation on chemical hazard precautions, such as state “right to know” laws, and OSHA document 29 CFR 1910 set the standards for chemical hazard communication (HAZCOM) and determine the types of documents that must be on file in a laboratory. For example, a yearly physical inventory of all hazardous chemicals must be performed, and MSDSs should be made available in each department for use. Each institution should also have at least one centralized area where all MSDSs are stored.
Occupational Exposure to Bloodborne Pathogens
The OSHA-mandated program, Occupational Exposure to Bloodborne Pathogens, became law in March 1992. This regulation requires that laboratories develop, implement, and comply with a plan that ensures the protective safety of laboratory staff to potential infectious bloodborne pathogens, hepatitis B virus (HBV), and human immunodeficiency virus (HIV). The law further specifies the rules for managing and handling medical waste in a safe and effective manner.
The CDC also recommends safety precautions concerning the handling of all patient specimens, known as standard precautions. The CLSI has also issued guidelines for the laboratory worker in regard to protection from bloodborne diseases spread through contact with patient specimens. In addition, the CDC provides recommendations for treatment after occupational exposure to potentially infectious material.
Avoiding Transmission of Infectious Diseases
History of Infectious Disease Prevention
The recognition of HIV-1 generated new policies from the CDC and mandated regulations by the OSHA. Current safety guidelines for the control of infectious disease are based on the original CDC publication, “Recommendations for Prevention of HIV Transmission in Health-Care Settings” (MMWR, Suppl 2S, 1987). Clarifications of safety practices appear in the 1988 CDC clarifications of the original guidelines (MMWR, 37(24), 1988); in the Department of Labor, OSHA’s “Occupational Exposure to Bloodborne Pathogens”: Part 1910 to title 29 of the Code of Federal Regulations, 64175–64182, (Fed Reg, 56(235), 1991); and in the U.S. Department of Health and Human Services’ “Regulations for Implementing the Clinical Laboratory Improvement Amendments of 1988: A Summary” (MMWR, 41(RR-2), 1992). Laboratory personnel must remain alert to further updates of these policies.
The purpose of the standards for bloodborne pathogens and occupational exposure is to provide a safe work environment. OSHA mandates that an employer does the following:
■ Educate and train all healthcare workers in standard precautions and in preventing bloodborne infections
■ Provide proper equipment and supplies, for example, gloves
■ Monitor compliance with the protective biosafety policies
HIV has been isolated from blood and body fluids, for example, semen, vaginal secretions, saliva, tears, breast milk, cerebrospinal fluid (CSF), amniotic fluid, and urine, but only blood, semen, vaginal secretions, and breast milk have been implicated in the transmission of HIV to date. Recently, sperm cells themselves have been discovered to be capable of transmitting HIV. Evidence for the role of saliva in the transmission of the virus is unclear, but standard precautions do not apply to saliva uncontaminated with blood.
Preventing Occupational Transmission of HBV and HIV
Blood is the single most important source of HIV, HBV, and other bloodborne pathogens in the occupational setting.
Needlestick Prevention
The CDC estimates that more than 380,000 needlestick injuries occur in US hospitals each year; approximately 61% of these injuries are caused by hollow-bore devices. Blood is the most frequently implicated infected body fluid in HIV and HBV exposure in the workplace.
An occupational exposure is defined as a percutaneous injury, for example, needlestick or cut with a sharp object, or contact by mucous membranes or nonintact skin (especially when the skin is chapped, abraded, or affected with dermatitis), or the contact is prolonged or involves an extensive area with blood, tissues, blood-stained body fluids, body fluids to which standard precautions apply, or concentrated virus.
Among healthcare personnel with documented occupationally acquired HIV infection, prior percutaneous exposure is the most prevalent route of infection. Certain percutaneous injuries carry a higher risk of infection. Risk of infection is greater with:
■ A deep injury
■ Late-stage HIV disease in the source patient
■ Visible blood on the device that caused the injury
■ Injury with a needle that had been placed in a source patient’s artery or vein
There are a small number of instances when HIV has been acquired through contact with nonintact skin or mucous membranes (i.e., splashes of infected blood in the eye or aerosols). The risk of infection not only varies with the type of exposure but also may be influenced by:
■ Amount of infected blood in the exposure
■ Length of contact with infectious material
■ Amount of virus in the patient’s blood or body fluid or tissue at the time of exposure
On November 6, 2000, the Needlestick Safety and Prevention Act became law. The provisions of the new law include:
■ Requires healthcare employers to provide safetyengineered sharp devices and needleless system to employees to reduce the risk of occupational exposure to HIV, hepatitis C, and other bloodborne disease.
■ Expands the defi nition of engineering controls to include devices with engineered sharps injury protection.
■ Requires that exposure control plans document consideration and implementation of safer medical devices designed to eliminate or minimize occupational exposure. These plans must be reviewed and updated at least annually.
■ Requires each healthcare facility to maintain a sharps injury log with detailed information regarding percutaneous injuries.
■ Requires employers to solicit input from healthcare workers when identifying and selecting sharps and document process.
■ Requires healthcare employers to provide safetyengineered sharp devices and needleless system to employees to reduce the risk of occupational exposure to HIV, hepatitis C, and other bloodborne disease.
■ Expands the defi nition of engineering controls to include devices with engineered sharps injury protection.
■ Requires that exposure control plans document consideration and implementation of safer medical devices designed to eliminate or minimize occupational exposure. These plans must be reviewed and updated at least annually.
■ Requires each healthcare facility to maintain a sharps injury log with detailed information regarding percutaneous injuries.
■ Requires employers to solicit input from healthcare workers when identifying and selecting sharps and document process.
The good news is that most occupational exposures do not result in infection. The average risk for HIV transmission after exposure to infected blood is low—about 3 per 1,000 injuries.
Sharps Prevention
The most widespread control measure required by OSHA and CLSI is the use of puncture-resistant sharps containers. (Fig. 1.1). The primary purpose of using these containers is to eliminate the need for anyone to transport needles and other sharps while looking for a place to discard them. Sharps containers are to be located in the patient areas as well as conveniently placed in the laboratory.
Phlebotomists should carry these red, puncture-resistant containers in their collection trays. Needle containers should not project from the top of the container. Use of the special sharps container permits quick disposal of a needle without recapping as well as of other sharp devices that may be contaminated with blood. This supports the recommendation against recapping, bending, breaking, or otherwise manipulating any sharp needle or lancet device by hand. Most needlestick accidents have occurred during recapping of a needle after a phlebotomy. Injuries also can occur to housekeeping personnel when contaminated sharps are left on a bed, concealed in linen, or disposed of improperly in a waste receptacle. Most accidental disposal-related exposures can be eliminated by the use of sharps containers. To discard sharps, containers are closed and placed in the biohazard waste. A needlestick injury must be reported to the supervisor or other designated individual.
Issues Related to HBV, HIV, and HCV Transmission
Medical personnel must be aware that HBV and HIV are totally different viruses. Exposure to HIV is uncommon, but cases of occupational transmission to healthcare personnel with no other known high-risk factors have been documented. Although HIV is an unlikely work-related hazard, it cannot be underrated because it can be fatal. The most feared hazard of all, the transmission of HIV through occupational exposure, is among the least likely to occur, if proper safety practices are followed. The transmission of HBV can also be fatal and is more probable than a transmission of HIV.
HBV can be present in extraordinarily high concentrations in blood, but HIV is usually found in lower concentrations. HBV may be stable in dried blood and blood products at 25°C for up to 7 days. HIV retains infectivity for more than 3 days in dried specimens at room temperature and for more than 1 week in an aqueous environment at room temperature.
HBV Vaccination
Before the advent of the hepatitis B vaccine, the leading occupationally acquired infection in healthcare workers was hepatitis B. Although the number of cases of hepatitis B in healthcare workers has sharply declined since hepatitis B vaccine became widely available in 1982, approximately 800 healthcare workers still become infected with HBV each year following occupational exposure. The likelihood of infection after exposure to blood infected with HBV or HIV depends on additional factors:
1. Concentration of HBV or HIV; viral concentration is higher for HBV than for HIV.
2. Presence of skin lesions or abrasions on the hands or exposed skin of the healthcare worker.
3. Immune status of the healthcare worker for HBV.
1. Concentration of HBV or HIV; viral concentration is higher for HBV than for HIV.
2. Presence of skin lesions or abrasions on the hands or exposed skin of the healthcare worker.
3. Immune status of the healthcare worker for HBV.
OSHA issued a federal standard in 1991 mandating employers to provide the hepatitis B vaccine to all employees who have or may have occupational exposure to blood or other potentially infective materials. The vaccine is to be offered at no expense to the employee, and if the employee refuses thevaccine, a declination form must be signed.
Vaccination against hepatitis B and compliance with precautions are the best prophylaxis against bloodborne pathogen exposure. If an individual has not been vaccinated, hepatitis B immune globulin (HBIG) is usually given concurrently with hepatitis B vaccine after exposure to penetrating injuries. If administered in accordance with the manufacturer’s directions, both products are considered safe and have been proven free of any risk of infection with HBV or HIV.
Vaccination against hepatitis B and compliance with precautions are the best prophylaxis against bloodborne pathogen exposure. If an individual has not been vaccinated, hepatitis B immune globulin (HBIG) is usually given concurrently with hepatitis B vaccine after exposure to penetrating injuries. If administered in accordance with the manufacturer’s directions, both products are considered safe and have been proven free of any risk of infection with HBV or HIV.
Postexposure Issues
Although the most important strategy for reducing the risk of occupational HIV transmission is to prevent occupational exposures, plans for postexposure management of healthcare personnel should be in place. The CDC has issued guidelines for the management of healthcare personnel exposures to HIV and recommendations for PEP. (Updated U.S. Public Health Service Guidelines for the Management of Occupational Exposures to HBV, HCV, and HIV and Recommendations for Postexposure Prophylaxis, MMWR, 50[RR-11], 2001).
An occupational exposure should be considered to be an urgent medical concern to ensure timely postexposure management. If an accidental occupational exposure does occur, laboratory staff members should be informed of options for treatment. Because a needlestick can trigger an emotional
response, it is wise to think about a course of action before the occurrence of an actual incident. If a “source patient” can be identified, part of the workup could involve testing the patient for various infectious diseases. Laws addressing the patient’s rights in regard to testing of a source patient can vary from state to state.
After skin or mucosal exposure to blood, the ACIP recommends immunoprophylaxis, depending on several factors. If an individual has not been vaccinated, HBIG is usually given, within 24 hours if practical, concurrently with hepatitis B vaccine postexposure injuries. HBIG contains antibodies to HBV and offers prompt but short-lived protection.
An exposed worker should be advised of and alerted to the risks of infection and evaluated medically for any history, signs, or symptoms consistent with HIV infection. Serologic testing for HIV antibodies should be made available to all healthcare workers who are concerned that they may have
been infected with HIV.
If a known or suspected parenteral exposure takes place, a laboratory professional may request follow-up monitoring for hepatitis or HIV antibodies. This monitoring and follow-up counseling must be provided free of charge. If voluntary informed consent is obtained, the source of the potentially infectious material and the technician/technologist should be tested immediately. The laboratory professional should also be tested at intervals after exposure. An injury report must be filed after parenteral exposure.
Immune globulin and antiviral agents (e.g., interferon with or without ribavirin) are not recommended for PEP of hepatitis C. For hepatitis C virus (HCV) postexposure management, the HCV status of the source and the exposed person should be determined. For healthcare personnel exposed to an HCV-positive source, follow-up HCV testing should be performed to determine if infection develops. After exposure to blood of a patient with (or with suspected) HCV infection, immune globulin should be given as soon as possible. No vaccine is currently available.
Immune Status: Screening and Vaccination
Screening of Employees
Screening is important for a variety of conditions. These include tuberculosis, rubella, and hepatitis B surface antigen.
Tuberculosis: Purifi ed Protein Derivative (PPD, Mantoux) Skin Test
If healthcare workers have recently spent time with and been exposed to someone with active tuberculosis (TB), their TB skin test reaction may not yet be positive. They may need a second skin test 10 to 12 weeks after the last time they had contact with the infected person. It can take several weeks after infection for the immune system to react to the TB skin test. If the reaction to the second test is negative, the worker probably does not have latent TB infection. Workers who have strongly positive reactions, with a skin test diameter greater than 15 mm, and symptoms suggestive of TB should be evaluated clinically and microbiologically. Two sputum specimens collected on successive days should be investigated for TB by microscopy and culture.
Rubella
All phlebotomists and laboratory staff need to demonstrate immunity to rubella. If antibody is not demonstrable, vaccination is necessary.
Hepatitis B Surface Antigen
All phlebotomists and laboratory staff need to demonstrate immunity to hepatitis B. If antibodies are not demonstrable, vaccination is necessary.
Vaccination of Employees
Individuals are recognized for being at risk for exposure to, and possible transmission of, diseases that can be prevented by immunizations. A well-planned and properly implemented immunization program is an important component of a healthcare organization’s infection prevention and control program. When planning these programs, valuable information is available from the Advisory Committee on Immunization Practices (ACIP), the Hospital Infection Control Practices Advisory Committee (HICPAC), and the CDC. Major considerations include the characteristics of the healthcare workers employed and the individuals served, as well as the requirements of regulatory agencies and local, state, and federal regulations. Preemployment health profiles with baseline screening of students and laboratory staff should include an immune status evaluation for hepatitis B,
rubella, and measles at a minimum.
See Box 1.2 for vaccines recommended for teens and college students.
BOX 1.2 1.2
Vaccines Recommended for Teens and College Students
■ Tetanus-Diphtheria-Pertussis vaccine
■ Meningococcal vaccine
■ HPV vaccine series
■ Hepatitis B vaccine series
■ Polio vaccine series
■ Measles-Mumps-Rubella (MMR) vaccine series
■ Varicella (chickenpox) vaccine series
■ Influenza vaccine
■ Pneumococcal polysaccharide vaccine (PPV)
■ Hepatitis A vaccine series
■ Annual Flu + H1N1 flu shot
Note: For complete statements by the Advisory Committee on Immunization Practices (ACIP), visit www.cdc.gov/vaccines/pubs/ACIP-list.htm.
Source: www.cdc.gov, retrieved January 5, 2010 (Vaccines Needed for Teens and College Students) and September 11, 2009 (H1N1 flu advisory, Recommended Vaccines).
SAFE WORK PRACTICES AND PROTECTIVE TECHNIQUES FOR INFECTION CONTROL
Safety Manual, Policies, and Practices
Each laboratory must have an up-to-date safety manual. This manual contains a comprehensive listing of approved policies, acceptable practices, and precautions including standard precautions. Specific regulations that conform to current state and federal requirements such as OSHA regulations
must be included in the manual. Other sources of mandatory and voluntary standards include the Joint Commission on Accreditation of Healthcare Organizations (JCAHO), the College of American Pathologists (CAP), and the CDC.
must be included in the manual. Other sources of mandatory and voluntary standards include the Joint Commission on Accreditation of Healthcare Organizations (JCAHO), the College of American Pathologists (CAP), and the CDC.
Each laboratory is required to evaluate the effectiveness of its plan at least annually and to update it as necessary. The written plan must be available to employees. A laboratory’s written plan must include the purpose and scope of the plan, references, definitions of terms and responsibilities, and
detailed procedural steps to follow.
Because many hazards in the clinical laboratory are unique, a special term, biohazard, was devised. This word is posted throughout the laboratory to denote infectious materials or agents that present a risk or even a potential risk to the health of humans or animals in the laboratory. The potential risk can be either through direct infection or through the environment. Infection can occur during the process of specimen collection or from handling, transporting, or testing the specimen.
Laboratory policies are included in a laboratory reference manual that is available to all hospital personnel. Such manuals that are frequently published online contain information regarding patient preparation for laboratory tests. Approved policies regarding the reporting of abnormal values are clearly stated in this document.
Standard Precautions
Standard precautions are intended to prevent occupational exposures to bloodborne pathogens. This approach eliminates the need for separate isolation procedures for patients known or suspected to be infectious. The application of standard precautions also eliminates the need for warning labels on specimens. According to the CDC concept of standard precautions, see CDC “Preventing Occupational HIV Transmission to Healthcare Personnel” (February 2002), all human blood and other body fl uids are treated as potentially infectious for HIV, HBV, and other bloodborne microorganisms that can cause disease in humans.
The risk of nosocomial transmission of HBV, HIV, and other bloodborne pathogens can be minimized if laboratory personnel are aware of and adhere to essential safety guidelines. The National Nosocomial Infections Surveillance (NNIS) System of the CDC estimates that nosocomial infections occur in 5% of all acute-care hospitalizations. In the United States, the incidence of hospital-acquired infection (HAI) is more than 2 million cases per year. Nosocomial infections can be caused by viral, bacterial, and fungal pathogens.
Handwashing
Frequent handwashing is an important safety precaution. It must be performed after contact with patients and laboratory specimens. Gloves should be used as an adjunct to, not a substitute for, handwashing.
The efficacy of handwashing in reducing transmission of microbial organisms has been demonstrated. At the very minimum, hands should be washed with soap and water (if visibly soiled) or by hand antisepsis with an alcohol-based handrub (if hands are not visibly soiled) in the following cases:
1. After completing laboratory work and before leaving the laboratory.
2. After removing gloves. The Association for Professionals in Infection Control and Epidemiology reports extreme variability in the quality of gloves, with leakage in 4% to 63% of vinyl gloves and in 3% to 52% of latex gloves.
3. Before eating, drinking, applying makeup, and changing contact lenses as well as before and after using the lavatory.
4. Before all activities that involve hand contact with mucous membranes or breaks in the skin.
5. Immediately after accidental skin contact with blood, body fluids, or tissues. If the contact occurs through breaks in gloves, the gloves should be removed immediately and the hands thoroughly washed. If accidental contamination occurs to an exposed area of the skin or because of a break in gloves, one must wash fi rst with a liquid soap, rinse well with water, and apply a 1:10 dilution of bleach
or 50% isopropyl or ethyl alcohol. The bleach or alcohol is left on the skin for at least 1 minute before the final washing with liquid soap and water.
2. After removing gloves. The Association for Professionals in Infection Control and Epidemiology reports extreme variability in the quality of gloves, with leakage in 4% to 63% of vinyl gloves and in 3% to 52% of latex gloves.
3. Before eating, drinking, applying makeup, and changing contact lenses as well as before and after using the lavatory.
4. Before all activities that involve hand contact with mucous membranes or breaks in the skin.
5. Immediately after accidental skin contact with blood, body fluids, or tissues. If the contact occurs through breaks in gloves, the gloves should be removed immediately and the hands thoroughly washed. If accidental contamination occurs to an exposed area of the skin or because of a break in gloves, one must wash fi rst with a liquid soap, rinse well with water, and apply a 1:10 dilution of bleach
or 50% isopropyl or ethyl alcohol. The bleach or alcohol is left on the skin for at least 1 minute before the final washing with liquid soap and water.
Two important points in the practice of hand hygiene technique are:
■ When decontaminating hands with a waterless antiseptic agent (e.g., an alcohol-based handrub), apply product to the palm of one hand and rub hands together, covering all surfaces of hands and fingers, until hands are dry. Follow the manufacturer’s recommendations on the volume of product to use. If an adequate volume of an alcoholbased handrub is used, it should take 15 to 25 seconds for hands to dry.
■ When washing with a nonantimicrobial or antimicrobial soap, wet hands fi rst with warm water, apply 3 to 5 mL of detergent to hands, and rub hands together vigorously for at least 15 seconds, covering all surfaces of the hands and fingers. Rinse hands with warm water and dry thoroughly with a disposable towel. Use the towel to turn off the faucet.
The Department of Health and Human Services (CDC) issued a draft guide in 2001 for Hand Hygiene in Healthcare Settings (see Box 1.3).
BOX 1.3
Guidelines for Handwashing and Hand Antisepsis in Healthcare Settings
1. Wash hands with a nonantimicrobial soap and water or an antimicrobial soap and water when hands are visibly dirty or contaminated with proteinaceous material.
2. Use an alcohol-based waterless antiseptic agent for routine decontamination of hands, if not visibly
soiled.
3. Waterless antiseptic agents are highly preferable, but hand antisepsis using antimicrobial soap may be considered in certain circumstances.
4. Decontaminate hands after contact with the patient’s skin.
5. Decontaminate hands after contact with blood and body fluids.
6. Decontaminate hands if moving from a contaminated area to clean body site during patient care.
7. Decontaminate hands after contact with inanimate objects in the immediate vicinity of a patient.
8. Decontaminate hands after removing gloves.
1. Wash hands with a nonantimicrobial soap and water or an antimicrobial soap and water when hands are visibly dirty or contaminated with proteinaceous material.
2. Use an alcohol-based waterless antiseptic agent for routine decontamination of hands, if not visibly
soiled.
3. Waterless antiseptic agents are highly preferable, but hand antisepsis using antimicrobial soap may be considered in certain circumstances.
4. Decontaminate hands after contact with the patient’s skin.
5. Decontaminate hands after contact with blood and body fluids.
6. Decontaminate hands if moving from a contaminated area to clean body site during patient care.
7. Decontaminate hands after contact with inanimate objects in the immediate vicinity of a patient.
8. Decontaminate hands after removing gloves.
Modified from Centers for Disease Control and Prevention, U.S. Department of Health and Human Services. Guideline for Hand Hygiene in Healthcare Settings, Morb Mortal Wkly Rep, 51(RR-16):1, 2002.
Personal Protective Equipment
OSHA requires laboratories to have a personal protective equipment (PPE) program. The components of this regulation include the following:
■ A workplace hazard assessment with a written hazard certification
■ Proper equipment selection
■ Employee information and training, with written competency certification
■ Regular reassessment of work hazards
■ A workplace hazard assessment with a written hazard certification
■ Proper equipment selection
■ Employee information and training, with written competency certification
■ Regular reassessment of work hazards
Laboratory personnel should not rely solely on devices for PPE to protect themselves against hazards. They also should apply PPE standards when using various forms of safety protection. A clear policy on institutionally required standard precautions is needed. For usual laboratory activities, PPE consists of gloves and a laboratory coat or gown. In a hematology laboratory, splash shields are also used.
Selection and Use of Gloves
Gloves for phlebotomy and laboratory work are nonsterile and made of vinyl or latex. There are no reported differences in barrier effectiveness between intact latex and intact vinyl gloves. Either type is usually satisfactory for phlebotomy and as a protective barrier when performing technical procedures. Latex-free gloves should be available for personnel with sensitivity to the typical glove material. In some laboratories, latex-free gloves are available for everyone to use.
Gloves for phlebotomy and laboratory work are nonsterile and made of vinyl or latex. There are no reported differences in barrier effectiveness between intact latex and intact vinyl gloves. Either type is usually satisfactory for phlebotomy and as a protective barrier when performing technical procedures. Latex-free gloves should be available for personnel with sensitivity to the typical glove material. In some laboratories, latex-free gloves are available for everyone to use.
Care must be taken to avoid indirect contamination of work surfaces or objects in the work area. Gloves should be properly placed on the hands and removed (see Fig. 1.2). An uncontaminated glove or paper towel is required before answering the telephone, handling laboratory equipment, or touching doorknobs.
The guidelines for the use of gloves during phlebotomy procedures are the following:
■ Must be worn when performing fi ngersticks or heel sticks on infants and children
■ Must be worn when receiving phlebotomy training
■ Should be changed between each patient contact
■ Must be worn when processing specimens
■ Must be worn when performing fi ngersticks or heel sticks on infants and children
■ Must be worn when receiving phlebotomy training
■ Should be changed between each patient contact
■ Must be worn when processing specimens
Facial Barrier Protection and Occlusive Bandages
Facial barrier protection (shields) should be used if there is a potential for splashing or spraying of blood or certain body fluids. Masks and facial protection should be worn if mucous membrane contact with blood or certain body fluid is anticipated. All disruptions of exposed skin should be covered with a water-impermeable occlusive bandage. This includes defects on the arms, face, and neck.
Laboratory Coats or Gowns as Barrier Protection
A color-coded, two–laboratory coat or equivalent system should be used whenever laboratory personnel are working with potentially infectious specimens. The coat worn in the laboratory must be changed or covered with an uncontaminated coat when leaving the immediate work area. Coats should be changed immediately if grossly contaminated with blood or body fluids, to prevent seepage through street clothes to the skin. Contaminated coats or gowns should be placed in an appropriately designated biohazard bag for laundering. Disposable plastic aprons are recommended if blood or certain body fluids may be splashed. Aprons should be discarded into a biohazard container.
A color-coded, two–laboratory coat or equivalent system should be used whenever laboratory personnel are working with potentially infectious specimens. The coat worn in the laboratory must be changed or covered with an uncontaminated coat when leaving the immediate work area. Coats should be changed immediately if grossly contaminated with blood or body fluids, to prevent seepage through street clothes to the skin. Contaminated coats or gowns should be placed in an appropriately designated biohazard bag for laundering. Disposable plastic aprons are recommended if blood or certain body fluids may be splashed. Aprons should be discarded into a biohazard container.
Decontamination of Work Surfaces, Equipment, and SpillsAll work surfaces are cleaned and sanitized at the beginning and end of the shift with a 1:10 dilution of household bleach (Table 1.1) or an EPA-registered disinfectant.
Disinfection describes a process that eliminates many or all pathogenic microorganisms, except bacterial spores, on inanimate objects. In healthcare settings, objects usually are disinfected by liquid chemicals or wet pasteurization. The effective use of disinfectants is part of a multibarrier strategy to prevent healthcare-associated infections. Surfaces are considered noncritical items because they contact intact skin. Use of noncritical items or contact with noncritical surfaces carries little risk of causing an infection in patients or staff.
Disinfecting Solutions
Hypochlorites are the most widely used of the chlorine disinfectants. The most prevalent chlorine products in the United States are aqueous solutions of 5.25% to 6.15% sodium hypochlorite, usually called household bleach. Bleach, a broad spectrum of antimicrobial activity, does not leave a toxic residue and is unaffected by water hardness. In addition, bleach is inexpensive and fast acting, removes dried or fixed microorganisms from surfaces, and has a low incidence of serious toxicity. A hazard is that sodium hypochlorite at the concentration used in household bleach can produce ocular irritation or oropharyngeal, esophageal, and gastric burns. The Environmental Protection Agency (EPA) has determined that the currently registered uses of hypochlorites will not result in unreasonable adverse effects to the environment.
Hypochlorites are the most widely used of the chlorine disinfectants. The most prevalent chlorine products in the United States are aqueous solutions of 5.25% to 6.15% sodium hypochlorite, usually called household bleach. Bleach, a broad spectrum of antimicrobial activity, does not leave a toxic residue and is unaffected by water hardness. In addition, bleach is inexpensive and fast acting, removes dried or fixed microorganisms from surfaces, and has a low incidence of serious toxicity. A hazard is that sodium hypochlorite at the concentration used in household bleach can produce ocular irritation or oropharyngeal, esophageal, and gastric burns. The Environmental Protection Agency (EPA) has determined that the currently registered uses of hypochlorites will not result in unreasonable adverse effects to the environment.
Hypochlorites are widely used in healthcare facilities in a variety of settings. Inorganic chlorine solution is used for spot disinfection of countertops and floors. A 1:10 to 1:100 dilution of 5.25% to 6.15% sodium hypochlorite (i.e., household bleach) can be used.
For small spills of blood (i.e., drops of blood) on noncritical surfaces, the area can be disinfected with a 1:100 dilution of 5.25% to 6.15% sodium hypochlorite or an EPA-registered tuberculocidal disinfectant. Because hypochlorites and other germicides are substantially inactivated in the presence of blood, large spills of blood require that the surface is cleaned before an EPA-registered disinfectant or a 1:10 (final concentration) solution of household bleach is applied. If a sharps injury is possible, the surface initially should be decontaminated and then cleaned and disinfected (1:10 final concentration).
An important issue concerning use of disinfectants for noncritical surfaces in healthcare settings is that the contact time specified on the label of the product is often too long to be practically followed. The labels of most products registered by EPA for use against HBV, HIV, or Mycobacterium tuberculosis specify a contact time of 10 minutes. Such a long contact time is not practical for disinfection of environmental surfaces in a healthcare setting because most healthcare facilities apply a disinfectant and allow it to dry (∼1 minute). Multiple scientific papers have demonstrated significant microbial reduction with contact times of 30 to 60 seconds.
Hypochlorite solutions in tap water at a pH > 8 stored at room temperature (23°C) in closed, opaque plastic containers can lose up to 40% to 50% of their free available chlorine level over 1 month. Sodium hypochlorite solution does not decompose after 30 days when stored in a closed brown bottle.
Disinfecting Procedure
While wearing gloves, employees should clean and sanitize all work surfaces at the beginning and end of their shift with a 1:10 dilution of household bleach. Instruments such as scissors or centrifuge carriages should be sanitized daily with a diluted solution of bleach. It is equally important to clean and disinfect work areas frequently during the workday as well as before and after the workday. Studies have demonstrated that HIV is inactivated rapidly after being exposed to common chemical germicides at concentrations that are much lower than those used in practice. Disposable materials contaminated with blood must be placed in containers marked “Biohazard” and properly discarded.
Neither HBV (or HCV) nor HIV has ever been documented as being transmitted from a housekeeping surface (e.g., countertops). However, an area contaminated by either blood or body fluids needs to be treated as potentially hazardous, with prompt removal and surface disinfection. Strategies differ for decontaminating spills of blood and other body fluids; the cleanup procedure depends on the setting (e.g., the porosity of the surface) and volume of the spill. The following protocol is recommended for managing spills in a clinical laboratory:
1. Wear gloves and a laboratory coat.
2. Absorb the blood with disposable towels. Remove as much liquid blood or serum as possible before decontamination.
3. Using a diluted bleach (1:10) solution, clean the spill site of all visible blood.
4. Wipe down the spill site with paper towels soaked with diluted bleach.
5. Place all disposable materials used for decontamination into a biohazard container.
6. Decontaminate nondisposable equipment by soaking overnight in a dilute bleach (1:10) solution and rinsing with methyl alcohol and water before reuse. Disposable glassware or supplies that have come in contact with the blood should be autoclaved or incinerated.
2. Absorb the blood with disposable towels. Remove as much liquid blood or serum as possible before decontamination.
3. Using a diluted bleach (1:10) solution, clean the spill site of all visible blood.
4. Wipe down the spill site with paper towels soaked with diluted bleach.
5. Place all disposable materials used for decontamination into a biohazard container.
6. Decontaminate nondisposable equipment by soaking overnight in a dilute bleach (1:10) solution and rinsing with methyl alcohol and water before reuse. Disposable glassware or supplies that have come in contact with the blood should be autoclaved or incinerated.
General Infection Control Safety Practices
All laboratories need programs to minimize risks to the health and safety of employees, volunteers, and patients. Suitable physical arrangements, an acceptable work environment, and appropriate equipment need to be available to maintain safe operations.
All laboratories need programs to minimize risks to the health and safety of employees, volunteers, and patients. Suitable physical arrangements, an acceptable work environment, and appropriate equipment need to be available to maintain safe operations.
A variety of other safety practices should be adhered to, to reduce the risk of inadvertent contamination with blood or certain body fluids. These practices include the following:
1. All devices in contact with blood that are capable of transmitting infection to the donor or recipient must be sterile and nonreusable.
2. Food and drinks should not be consumed in work areas or stored in the same area as specimens. Containers, refrigerators, or freezers used for specimens should be marked as containing a biohazard.
3. Specimens needing centrifugation should be capped and placed into a centrifuge with a sealed dome.
4. Rubber-stoppered test tubes are opened slowly and carefully with a gauze square over the stopper to minimize aerosol production (the introduction of substances into the air).
5. Autodilutors or safety bulbs are used for pipetting. Pipetting of any clinical material by mouth is strictly forbidden (see the following discussion).
6. No tobacco products can be used in the laboratory.
7. No manipulation of contact lenses or teeth-whitening strips should be done with gloved or potentially infectious hands.
8. Do not apply lipstick or makeup.
9. All personnel should be familiar with the location and use of eyewash stations and safety showers.
Pipetting Safeguards: Automatic Devices
Pipetting must be done by mechanical means. Such a device is a bottle top dispenser that can be used to deliver repetitive aliquots of reagents. It is designed as a bottle-mounted system that can dispense selected volumes in an easy, precise manner. It is usually trouble free and requires minimal maintenance.
Specimen-Processing Protection
Protective gloves should always be worn for handling any type of biological specimen. Biohazards are generally treated with great respect in the clinical laboratory (see Fig. 1.3). The adverse effects of pathogenic substances on the body are well documented.
The presence of pathogenic organisms is not limited to the culture plates in the microbiology laboratory. Airborne infectious particles, or aerosols, can be found in all areas of the laboratory where human specimens are used.
In the hematology laboratory, centrifuge accidents, or the improper removal of rubber stoppers from test tubes, produce airborne droplets (aerosols) that can result in an occupational exposure. If these aerosol products are infectious and come in direct contact with mucous membranes or nonintact skin, direct transmission of virus can potentially result.
When the cap is being removed from a specimen tube or a blood collection tube, the top should be covered with a disposable gauze pad or a special protective pad. Gauze pads with an impermeable plastic coating on one side can reduce contamination of gloves. The tube should be held away from the body and the cap gently twisted to remove it. Snapping off the cap or top can cause some of the contents to aerosolize. When not in place on the tube, the cap should still be kept in the gauze and not placed directly on the work surface or countertop.
When specimens are being centrifuged, the tube caps should always be kept on the tubes. Centrifuge covers must be used and left on until the centrifuge stops. The centrifuge should be allowed to stop by itself and should not be manually stopped by the worker.
Another step that should be taken to control the hazard from aerosols is to exercise caution in handling pipettes and other equipment used to transfer human specimens, especially pathogenic materials. These materials should be discarded properly and carefully.
Specially constructed plastic splash shields are used in many laboratories for the processing of blood specimens. The tube caps are removed behind or under the shield, which acts as a barrier between the person and the specimen tube. This is designed to prevent aerosols from entering the nose, eyes, or mouth. Laboratory safety boxes are commercially available and can be used to remove stoppers from tubes or perform other procedures that might cause spattering. Splash shields and safety boxes should be periodically decontaminated.
Specimen-Handling and Shipping Requirements
The proper handling of blood and body fluids is critical to the accuracy of laboratory test results, and the safety of all individuals who come in contact with specimens must be guaranteed. If a blood specimen is to be transported, the shipping container must meet OSHA requirements for shipping clinical specimens (Federal Register 29, CAR 1910.1030). Shipping containers must meet the packaging requirements of major couriers and Department of Transportation hazardous materials regulations. Approved reclosable plastic bags for handling biohazardous specimens and amber bags for specimens for analysis of light-sensitive drugs are available. These bags must meet the NCCLS M29-A3 specimen handling guidelines. Approved bags have bright orange and black graphics that clearly identify bags as holding hazardous materials (Fig. 1.4).
The proper handling of blood and body fluids is critical to the accuracy of laboratory test results, and the safety of all individuals who come in contact with specimens must be guaranteed. If a blood specimen is to be transported, the shipping container must meet OSHA requirements for shipping clinical specimens (Federal Register 29, CAR 1910.1030). Shipping containers must meet the packaging requirements of major couriers and Department of Transportation hazardous materials regulations. Approved reclosable plastic bags for handling biohazardous specimens and amber bags for specimens for analysis of light-sensitive drugs are available. These bags must meet the NCCLS M29-A3 specimen handling guidelines. Approved bags have bright orange and black graphics that clearly identify bags as holding hazardous materials (Fig. 1.4).
Some products have an additional marking area that allows phlebotomists to identify contents that must be kept frozen, refrigerated, or at room temperature. Maintaining specimens at the correct preanalytical (preexamination) temperature is extremely important. Products such as the Insul-Tote (Palco Labs) are convenient for specimen transport from the field to the clinical laboratory. This particular product has a reusable cold gel pack that keeps temperatures below 70°F for 8 hours even if the exterior temperature is above 100°F. Many laboratory courier services use everyday household coolers.
Blood specimen collection and processing should conform with the current checklist requirements adopted by the CAPs (http://www.cap.org). Errors in specimen collection and handling, preanalytical (preexamination) errors, are a significant cause of erroneous results.
Storage of Processed Specimens
Some specimens must be analyzed immediately after they reach the laboratory. Blood specimens for hematology studies can be stored in the refrigerator for 2 hours before being used in testing. After storage, anticoagulated blood must be thoroughly mixed after it has reached room temperature.
Some specimens must be analyzed immediately after they reach the laboratory. Blood specimens for hematology studies can be stored in the refrigerator for 2 hours before being used in testing. After storage, anticoagulated blood must be thoroughly mixed after it has reached room temperature.
Plasma and serum often can be frozen and preserved satisfactorily until a determination can be done. Whole blood cannot be frozen because RBCs rupture on freezing. Freezing preserves heat-sensitive coagulation factors. A laboratory determination is best done on a fresh specimen.
OSHA Medical Waste Standards
OSHA standards provide for the implementation of a waste disposal program (see Box 1.4). On the federal level, the storage and management of medical waste is primarily regulated by OSHA. Laws and statutes are defined by the Occupational Health and Safety Act and the Clean Air Act.
BOX 1.4
BOX 1.4
OSHA Regulation of Medical Waste
■ Contaminated reusable sharps must be placed in containers that are puncture resistant; labeled or color coded; and leakproof on the sides and bottom. Reusable sharps that are contaminated with blood or other potentially infectious materials must not be stored or processed in a manner that requires employees to reach by hand into the containers.
■ Specimens of blood or other potentially infectious material are required to be placed in a container that is labeled or color coded and closed prior to being stored, transported, or shipped. Contaminated sharps must be placed in containers that are closeable, puncture resistant, leakproof on sides and bottoms, and labeled or color coded.
■ Regulated wastes (liquid or semiliquid blood or other potentially infectious materials; contaminated items that would release blood or other potentially infectious materials in a liquid or semiliquid state if compressed; items that are caked with dried blood or other potentially infectious materials and are capable of releasing these materials during handling; contaminated sharps; and pathological and microbiological wastes containing blood or other potentially infectious materials) must be placed in containers that are closeable, constructed to contain all contents and prevent leakage of fluids, labeled or color coded, and closed prior to removal (see a full discussion below of biohazard containers and biohazard bag).
■ All bins, pails, cans, and similar receptacles intended for reuse, which have the likelihood of becoming contaminated with blood or other potentially infectious materials, are required to be inspected and decontaminated on a regularly scheduled basis. Waste containers must be easily accessible to personnel and must be located in the laboratory areas where they are typically used. Containers for waste should be constructed so that their contents will not be spilled if the container is
tipped over accidentally.
■ Labels affixed to containers of regulated waste; refrigerators and freezers containing blood or other potentially infectious materials; and other containers used to store, transport, or ship blood or other potentially infectious materials must include the biohazard symbol; be fluorescent orange or orange-red or predominantly so, with lettering and symbols in contrasting color; and be affi xed as closely as possible to the container by adhesive or wire to prevent loss or removal.
■ Contaminated reusable sharps must be placed in containers that are puncture resistant; labeled or color coded; and leakproof on the sides and bottom. Reusable sharps that are contaminated with blood or other potentially infectious materials must not be stored or processed in a manner that requires employees to reach by hand into the containers.
■ Specimens of blood or other potentially infectious material are required to be placed in a container that is labeled or color coded and closed prior to being stored, transported, or shipped. Contaminated sharps must be placed in containers that are closeable, puncture resistant, leakproof on sides and bottoms, and labeled or color coded.
■ Regulated wastes (liquid or semiliquid blood or other potentially infectious materials; contaminated items that would release blood or other potentially infectious materials in a liquid or semiliquid state if compressed; items that are caked with dried blood or other potentially infectious materials and are capable of releasing these materials during handling; contaminated sharps; and pathological and microbiological wastes containing blood or other potentially infectious materials) must be placed in containers that are closeable, constructed to contain all contents and prevent leakage of fluids, labeled or color coded, and closed prior to removal (see a full discussion below of biohazard containers and biohazard bag).
■ All bins, pails, cans, and similar receptacles intended for reuse, which have the likelihood of becoming contaminated with blood or other potentially infectious materials, are required to be inspected and decontaminated on a regularly scheduled basis. Waste containers must be easily accessible to personnel and must be located in the laboratory areas where they are typically used. Containers for waste should be constructed so that their contents will not be spilled if the container is
tipped over accidentally.
■ Labels affixed to containers of regulated waste; refrigerators and freezers containing blood or other potentially infectious materials; and other containers used to store, transport, or ship blood or other potentially infectious materials must include the biohazard symbol; be fluorescent orange or orange-red or predominantly so, with lettering and symbols in contrasting color; and be affi xed as closely as possible to the container by adhesive or wire to prevent loss or removal.
Source: www.fedcenter.gov
QUALITY ASSESSMENT IN THE HEMATOLOGY LABORATORY
The assessment of quality results for the various analyses is critical and is an important component of the operation of a high-quality laboratory. Quality assessment programs monitor the following:
■ Test request procedures
■ Patient identification
■ Specimen procurement
■ Specimen labeling
■ Specimen transportation and processing procedures
■ Laboratory personnel performance
■ Laboratory instrumentation, reagents, and analytical (examination) test procedures
■ Turnaround times
■ Accuracy of the final result
■ Test request procedures
■ Patient identification
■ Specimen procurement
■ Specimen labeling
■ Specimen transportation and processing procedures
■ Laboratory personnel performance
■ Laboratory instrumentation, reagents, and analytical (examination) test procedures
■ Turnaround times
■ Accuracy of the final result
Complete documentation of all procedures involved in obtaining the analytical (examination) result for the patient sample must be maintained and monitored in a systematic manner.
Regulations and Organizations Impacting Quality
Clinical Laboratory Improvement Amendments
In 1988, the U.S. Congress enacted the Clinical Laboratory Improvement Amendments of 1988 (CLIA’88) in response to the concerns about laboratory testing errors. The final CLIA rule, Laboratory Requirements Relating to Quality Systems and Certain Personnel Qualifications, was published in the Federal Register on January 24, 2003. Enactment of CLIA established a minimum threshold for all aspects of clinical laboratory testing. CLIA’88 also incorporates proficiency testing in the regulations.
In 1988, the U.S. Congress enacted the Clinical Laboratory Improvement Amendments of 1988 (CLIA’88) in response to the concerns about laboratory testing errors. The final CLIA rule, Laboratory Requirements Relating to Quality Systems and Certain Personnel Qualifications, was published in the Federal Register on January 24, 2003. Enactment of CLIA established a minimum threshold for all aspects of clinical laboratory testing. CLIA’88 also incorporates proficiency testing in the regulations.
Voluntary Accrediting Organizations
Voluntary accrediting agencies, for example, the Joint Commission on Accreditation of Healthcare Organization and the CAP, have set standards that include quality assessment programs.
ISO 15189
The International Organization for Standardization (ISO), a network of the national standards institutes of 159 countries, is the world’s largest developer and publisher of international standards. ISO is a nongovernmental organization that forms a bridge between the public and private sectors. ISO standards and certification are widely used by industry but now ISO 15189 has been formulated for clinical laboratories. The standard, ISO 15189, is based on ISO/IEC 17025, the main standard used by testing and calibration laboratories, and ISO 9001. The 15189 standard was developed with the input of the CAP and has gained acceptance as a mandatory accreditation in Australia, the Canadian province of Ontario, and many European countries. In the United States, 15189 accreditation remains optional.
ISO 15189:2007 is for use by medical laboratories in developing their quality management systems and assessing their own competence and for use by accreditation bodies in confirming or recognizing the competence of medical laboratories.
The International Organization for Standardization (ISO), a network of the national standards institutes of 159 countries, is the world’s largest developer and publisher of international standards. ISO is a nongovernmental organization that forms a bridge between the public and private sectors. ISO standards and certification are widely used by industry but now ISO 15189 has been formulated for clinical laboratories. The standard, ISO 15189, is based on ISO/IEC 17025, the main standard used by testing and calibration laboratories, and ISO 9001. The 15189 standard was developed with the input of the CAP and has gained acceptance as a mandatory accreditation in Australia, the Canadian province of Ontario, and many European countries. In the United States, 15189 accreditation remains optional.
ISO 15189:2007 is for use by medical laboratories in developing their quality management systems and assessing their own competence and for use by accreditation bodies in confirming or recognizing the competence of medical laboratories.
Components of Quality Assessment
■ A Quality Assessment system is divided into two major components: nonanalytical factors and the analysis of quantitative data (quality control [QC]).
Quality Assessment is used in the clinical hematology laboratory to ensure excellence in performance. A systematic approach to quality assures that correct laboratory results are obtained in the shortest possible time and at a reasonable cost.
The total testing process (TTP) serves as the primary point of reference for focusing on quality in the clinical laboratory. TTP is defined by activities in three distinct phases related to workflow outside and inside the laboratory:
1. Preanalytical (preexamination)
2. Analytical (examination)
3. Postanalytical (post-examination)
1. Preanalytical (preexamination)
2. Analytical (examination)
3. Postanalytical (post-examination)
Nonanalytical Factors in Quality Assessment
To guarantee the highest quality patient care through laboratory testing, a variety of preanalytical (preexamination) and Postanalytical (post-examination) factors in addition to analytical (examination) data must be considered. For laboratories to comply with CLIA’88 and be certified to perform testing, they must meet minimum standards. In some cases, deficiencies are noted and must be corrected.
Nonanalytical factors that support quality testing include the following:
1. Qualified personnel
2. Laboratory policies
3. Laboratory procedure manual
4. Test requisitioning
5. Patient identification and specimen procurement and labeling
6. Specimen collection, transport, processing and storage
7. Preventive maintenance of equipment
8. Appropriate methodology
9. Accuracy in reporting results and documentation
1. Qualified personnel
2. Laboratory policies
3. Laboratory procedure manual
4. Test requisitioning
5. Patient identification and specimen procurement and labeling
6. Specimen collection, transport, processing and storage
7. Preventive maintenance of equipment
8. Appropriate methodology
9. Accuracy in reporting results and documentation
Qualified Personnel
The entry-level examination competencies of all certified persons in hematology must be validated. Validation takes the form of both external certification and new employee orientation to the work environment.
The entry-level examination competencies of all certified persons in hematology must be validated. Validation takes the form of both external certification and new employee orientation to the work environment.
Continuing competency is equally important. Participation in continuing education activities is essential to the maintenance of competency and is required in some instances to maintain professional certification. Personnel performance should be monitored with periodic evaluations and reports. Quality assessment demands that a supervisor monitors the results of daily work and that all analytical (examination) reports produced during a particular shift be evaluated for errors and omissions.
Laboratory Policies
Laboratory policies should be included in a laboratory reference manual that is available to all hospital personnel. Each laboratory must have an up-to-date safety manual. This manual contains a comprehensive listing of approved policies, acceptable practices, and precautions, including standard blood and body fluid precautions. Specific regulations that conform to current state and general requirement, such as OSHA regulations, must be included in the manual. Other sources of mandatory and voluntary standards include JCAHO, CAP, and the CDC.
Laboratory policies should be included in a laboratory reference manual that is available to all hospital personnel. Each laboratory must have an up-to-date safety manual. This manual contains a comprehensive listing of approved policies, acceptable practices, and precautions, including standard blood and body fluid precautions. Specific regulations that conform to current state and general requirement, such as OSHA regulations, must be included in the manual. Other sources of mandatory and voluntary standards include JCAHO, CAP, and the CDC.
Laboratory Procedure Manual
Laboratory procedures should be contained in a current and complete document of laboratory procedures, including approved policies for the reporting of results. The manual must be reviewed regularly, in some cases annually, by the supervisory staff and updated, as needed.
Laboratory procedures should be contained in a current and complete document of laboratory procedures, including approved policies for the reporting of results. The manual must be reviewed regularly, in some cases annually, by the supervisory staff and updated, as needed.
The laboratory procedure manual describes each procedure performed in the hematology laboratory. This manual must comply with the CLSI format standards for a procedure manual. CLSI is an internationally recognized group of laboratory professionals who lead Quality Assessment efforts. To support a QC program, methods for documenting laboratory results must be included in the procedure manual. Proper documentation ensures that control specimens have been properly monitored. The procedural format found in Chapter 26 of this book follows the CLSI guidelines.
The CLSI recommends that the procedure manual follows a specific pattern of organization. Each assay done in the hematology laboratory must be included in the manual. The minimal components are as follows:
■ Title of the assay
■ Principle of the procedure and statement of clinical applications
■ Protocol for specimen collection and storage
■ QC information
■ Reagents, supplies, and equipment
■ Procedural protocol
■ Reference “normal” ranges
■ Technical sources of error
■ Limitations of the procedure
■ Proper procedures for specimen collection and storage
■ Approved policies for the reporting of results
■ Title of the assay
■ Principle of the procedure and statement of clinical applications
■ Protocol for specimen collection and storage
■ QC information
■ Reagents, supplies, and equipment
■ Procedural protocol
■ Reference “normal” ranges
■ Technical sources of error
■ Limitations of the procedure
■ Proper procedures for specimen collection and storage
■ Approved policies for the reporting of results
Test Requisitioning
A laboratory test can be requested by a primary care provider or, in some states, the patient. The request, either hard copy or electronic, must include the patient identification data, the time and date of specimen collection, the source of the specimen, and the analyses to be performed. The information on the accompanying specimen container must match exactly the patient identification on the test request. The information needed by the physician to assist in ordering tests must be included in an online database or printed handbook.
A laboratory test can be requested by a primary care provider or, in some states, the patient. The request, either hard copy or electronic, must include the patient identification data, the time and date of specimen collection, the source of the specimen, and the analyses to be performed. The information on the accompanying specimen container must match exactly the patient identification on the test request. The information needed by the physician to assist in ordering tests must be included in an online database or printed handbook.
Patient Identifi cation, Specimen Procurement, and Labeling
Maintaining an electronic database or handbook of specimen requirement information is one of the first steps in establishing a quality assessment program for the clinical laboratory. Current information about obtaining appropriate specimens, special collection requirements for various types of tests, ordering tests correctly, and transporting and processing specimens appropriately should be included in the database.
Patients must be carefully identified. Preanalytical (preexamination) errors are the most common source of laboratory errors (see Box 1.5). For example, identification errors, either of the patient or of the specimen, are major potential sources of error. The use of computerized bar code identification of
specimens is an asset to specimen identification. Using established specimen requirement information, the clinical specimens must be properly labeled once they have been obtained from the patient. Computer-generated bar code labels (Fig. 1.5) assist in making certain that proper patient identification is noted on each specimen container sent to the laboratory. An important rule to remember is that the analytical result can only be as good as the received specimen.
specimens is an asset to specimen identification. Using established specimen requirement information, the clinical specimens must be properly labeled once they have been obtained from the patient. Computer-generated bar code labels (Fig. 1.5) assist in making certain that proper patient identification is noted on each specimen container sent to the laboratory. An important rule to remember is that the analytical result can only be as good as the received specimen.
BOX 1.5
Examples of Potential Preanalytical (preexamination)/Analytical (examination)/Postanalytical (post-examination) Errors
PREANALYTICAL (PREEXAMINATION)
■ Specimen obtained from the wrong patient
■ Specimen procured at the wrong time
■ Specimen collected in the wrong tube or container
■ Blood specimens collected in the wrong order
■ Incorrect labeling of specimen
■ Improper processing of specimen
■ Specimen obtained from the wrong patient
■ Specimen procured at the wrong time
■ Specimen collected in the wrong tube or container
■ Blood specimens collected in the wrong order
■ Incorrect labeling of specimen
■ Improper processing of specimen
ANALYTICAL (EXAMINATION)
■ Oversight of instrument flags
■ Out-of-control QC results
■ Wrong assay performed
POSTANALYTICAL (POST-EXAMINATION)
■ Verbal reporting of results
■ Instrument: Laboratory Information System (LIS) incompatibility error
■ Confusion about reference ranges
■ Failure to report critical values immediately
Specimen Collection, Transporting, Processing and Storage
Strict adherence to correct procedures for specimen collection and storage is critical to the accuracy of any test.
Specimens must be efficiently transported to the laboratory. Some assays require special handling conditions, such as placing the specimen on ice immediately after collection. Specimens should be tested within 2 hours of collection to produce accurate results. The documentation of specimen arrival times in the laboratory as well as other specific test request data is an important aspect of the quality assessment process. It is important that the laboratory processing system is able to track a specimen.
Correct storage of specimens is critical to obtaining accurate results. Specimen integrity is an important issue when blood is collected at a site away from the testing facility. Samples may need to be drawn several hours before testing. In many cases, cooling of specimens on ice is critical. This is particularly true for coagulation testing (e.g., prothrombin time [PT] and activated partial thromboplastin time [aPTT]).
According to CLSI (Collection, Transport, and Processing of Blood Specimens for Testing Plasma-Based Coagulation Assays, 5th ed, Approved Guidelines, H21-A5, 2008), blood samples collected for PT and aPTT analysis in tubes with sodium citrate should be handled using the following sample protocol when collected off-site. The sample tube should remain unopened before testing. Centrifugation and testing of such samples can be delayed for up to 2 hours at 22° to 24°C (71.6° to 75.2°F) or for up to 4 hours at 2° to 4°C (35.6° to 39.2°F). The sample must be kept in a well-chilled, properly insulated cooler or a refrigerated block. Either storage device must have a thermometer to monitor its temperature to prevent overheating or partial freezing of whole blood samples. Separation of the sample upon standing should not affect sample integrity. In addition, this method of storage should be confi rmed for compatibility by contacting both the manufacturer of the evacuated tube collection system and the technical supervisor of coagulation testing.
Preventive Maintenance of Equipment
Monitoring of the temperatures of equipment and refrigerators is important to the quality of test performance. Microscopes, centrifuges, and other pieces of equipment need regularly to be cleaned and checked for accuracy. A preventive maintenance schedule should be followed for all automated equipment.
Monitoring of the temperatures of equipment and refrigerators is important to the quality of test performance. Microscopes, centrifuges, and other pieces of equipment need regularly to be cleaned and checked for accuracy. A preventive maintenance schedule should be followed for all automated equipment.
Equipment such as microscopes, centrifuges, and spectrophotometers should be cleaned and checked for accuracy on a regular schedule. A preventive maintenance schedule should be followed (refer to the section “Instrument Protocol,” Chapter 27 for examples) for all pieces of automated equipment (e.g., cell-counting instruments). Failure to monitor equipment regularly can produce inaccurate test results and lead to expensive repairs.
Manufacturers will recommend a calibration frequency determined by measurement system stability and will communicate in product inserts the specific criteria for mandatory recalibration of instrument systems. These may include the following:
■ Instrument maintenance
■ Reagent lot change
■ Major component replacement
■ New software installation
Clinical laboratories must follow CLIA or the manufacturer’s requirements for instrument calibration frequency, whichever is most stringent. CLIA requires that laboratories recalibrate an analytical (examination) method at least every 6 months.
Appropriate Methodology
When new methods are introduced, it is important to check the procedure for accuracy and variability. Replicate analyses using control specimens are recommended to check for accuracy and to eliminate factors such as day-to-day variability, reagent variability, and differences between
technologists.
When new methods are introduced, it is important to check the procedure for accuracy and variability. Replicate analyses using control specimens are recommended to check for accuracy and to eliminate factors such as day-to-day variability, reagent variability, and differences between
technologists.
A template for a standard protocol for the introduction of new testing into a clinical laboratory is presented in Box 1.6.
BOX 1.6
Seven Steps for New Assay Development
STEP 1: SELECT AN ASSAY
Determine the need for the assay, the volume of tests and cost-effectiveness, and site of testing.
Determine the need for the assay, the volume of tests and cost-effectiveness, and site of testing.
STEP 2: RESEARCH ISSUES RELATED TO TESTING
Analyze physical and financial requirements, workflow analysis, and required approvals.
STEP 3: NEGOTIATE WITH VENDORS
Communicate with vendors to evaluate related equipment and supplies, validation panels, and related training and education.
STEP 4: MAKE A DECISION
“Which particular assay or multiple assays will optimally meet the specified needs of the laboratory?”
“Do the cost/benefit ratio, demand for the assay, and quality of available products meet the requirements established by due diligence (Step 2)?”
“Can special requirements for the performance of the assay be met?”
STEP 5: ESTABLISH SPECIFIC REQUIREMENTS
Determine FDA status of assay, the CLIA’88 level of complexity of the assay, parameters of validation study, and the method of documentation consistent with good laboratory practices (GLP).
STEP 6: DEVELOP DOCUMENTATION
Write a standard operating procedure (SOP) for the assay including the technical procedure and QC log, and monitor, assess, and correct problems. A quality assessment document should be included to designate responsible staff, verification of results, proficiency testing, and maintenance of all regulations. Other supplemental documents can include logs of patients, inventory, discrepant results, temperature log, and personnel training.
Write a standard operating procedure (SOP) for the assay including the technical procedure and QC log, and monitor, assess, and correct problems. A quality assessment document should be included to designate responsible staff, verification of results, proficiency testing, and maintenance of all regulations. Other supplemental documents can include logs of patients, inventory, discrepant results, temperature log, and personnel training.
STEP 7: CONDUCT AND ASSESS TRAINING AND PROFICIENCY
After selection of personnel for training, the actual training is conducted. Competency evaluations should be conducted initially and periodically (after 6 months, after 1 year, and annually). Proficiency testing is conducted to verify accuracy and reliability of testing. The frequency of testing is determined by regulatory agencies.
Source: Lazzari MA. LABMEDICINE. 40(7):2009, 389–393.
Accuracy in Reporting Results and Documentation
Many laboratories have established critical values or the Delta check system to monitor individual patient results. The difference between a patient’s present laboratory result and consecutive previous results that exceed a predefined limit is referred to as a Delta check. An abrupt change, high or low, can trigger this computer-based warning system and needs to be investigated before reporting a patient result. Delta checks are investigated by the laboratory internally to rule out errors, for example, mislabeling of a specimen.
Many laboratories have established critical values or the Delta check system to monitor individual patient results. The difference between a patient’s present laboratory result and consecutive previous results that exceed a predefined limit is referred to as a Delta check. An abrupt change, high or low, can trigger this computer-based warning system and needs to be investigated before reporting a patient result. Delta checks are investigated by the laboratory internally to rule out errors, for example, mislabeling of a specimen.
Highly abnormal individual test values and significant differences from previous results in the Delta check system alert the technologist to a potential problem. At times, a phone call to the primary care provider may be made by the laboratory technologist to investigate possible preanalytical (preexamination) errors such as:
1. Obtaining specimens from IV lines
2. Specimen processing error
3. Actual changes in a patient’s clinical condition
Other quantitative control systems (discussed later) are also used to ensure the quality of test results.
Reporting Results
The ongoing process of making certain that the correct laboratory result is reported for the right patient in a timely manner and at the correct cost is known as continuous quality improvement (CQI). This process assures the clinician ordering the test that the testing process has been done in the best possible way to provide the most useful information in diagnosing or managing the particular patient
in question. Quality assessment indicators are evaluated as part of the CQI process. Each laboratory will set its own indicators, depending on the specific goals of the laboratory. Any quality assessment indicators should be appreciated as a tool to ensure that reported results are of the highest quality.
The ongoing process of making certain that the correct laboratory result is reported for the right patient in a timely manner and at the correct cost is known as continuous quality improvement (CQI). This process assures the clinician ordering the test that the testing process has been done in the best possible way to provide the most useful information in diagnosing or managing the particular patient
in question. Quality assessment indicators are evaluated as part of the CQI process. Each laboratory will set its own indicators, depending on the specific goals of the laboratory. Any quality assessment indicators should be appreciated as a tool to ensure that reported results are of the highest quality.
Documentation is an important aspect of quality assessment. CLIA regulations mandate that any problem or situation that might affect the outcome of a test result be recorded and reported. All such incidents must be documented in writing, including the changes proposed and their implementation, and follow-up monitored.
Another valuable quality assessment technique is to look at the data generated for each patient and inspect the relationships between them. These many relationships include the relationship between hemoglobin and hematocrit and the appearance of the blood smear on microscopic examination.
Documentation
The use of laboratory computer systems and information processing expedites record keeping. Quality assessment programs require documentation, and computer record–keeping capability assists in this effort. When control results are within the acceptable limits established by the laboratory, these data provide the necessary link between the control and patient data, thus giving reassurance that the patient results are reliable, valid, and reportable. This information is necessary to document that uniform protocols have been established and that they are being followed. The data can also support the proper functioning capabilities of test systems being used at the time patient results are produced.
The use of laboratory computer systems and information processing expedites record keeping. Quality assessment programs require documentation, and computer record–keeping capability assists in this effort. When control results are within the acceptable limits established by the laboratory, these data provide the necessary link between the control and patient data, thus giving reassurance that the patient results are reliable, valid, and reportable. This information is necessary to document that uniform protocols have been established and that they are being followed. The data can also support the proper functioning capabilities of test systems being used at the time patient results are produced.
QUALITY CONTROL IN THE HEMATOLOGY LABORATORY
QC monitors the accuracy and precision of test performance over time.
The purpose of QC is to detect errors that result from:
■ Test system failure
■ Adverse environmental conditions
■ Variance, a general term that describes the factors or fluctuations that affect the measurement, in operator performance
QC monitors the accuracy and precision of test performance over time.
The purpose of QC is to detect errors that result from:
■ Test system failure
■ Adverse environmental conditions
■ Variance, a general term that describes the factors or fluctuations that affect the measurement, in operator performance
It is important for hematology technologists or technicians to understand basic statistical concepts used in QC. Knowledge of specific elements of statistics is important in hematology for two reasons:
1. Application of statistical analysis of results in Quality Assessment protocols
2. Instrumental applications of statistics to erythrocyte, leukocyte, and platelet reports
Accrediting agencies require monitoring and documentation of QC records. CLIA states, “The laboratory must establish and follow written quality control procedures for monitoring and evaluating the quality of the analytical (examination) testing process of each method to assure the accuracy and reliability of patient test results and reports.” For tests of moderate complexity, CLIA states that laboratories comply with the more stringent of the following requirements:
■ Perform and document control procedures using at least two levels of control material each day of testing.
■ Follow the manufacturer’s instructions for QC. QC activities include monitoring the performance of laboratory instruments, reagents, other testing products, and equipment. A written record of QC activities for each procedure or function should include details of deviation from the usual results, problems, or failures in functioning or in the analytical (examination) procedure and any corrective action taken in response to these problems.
■ Perform and document control procedures using at least two levels of control material each day of testing.
■ Follow the manufacturer’s instructions for QC. QC activities include monitoring the performance of laboratory instruments, reagents, other testing products, and equipment. A written record of QC activities for each procedure or function should include details of deviation from the usual results, problems, or failures in functioning or in the analytical (examination) procedure and any corrective action taken in response to these problems.
Documentation of QC includes preventive maintenance records, temperature charts, and QC charts for specific assays. All products and reagents used in the analytical (examination) procedures must be carefully checked before actual use in testing patient samples. Use of QC specimens, proficiency testing, and standards depends on the specific requirements of the accrediting agency.
Terms Used in Clinical Quality Control
In the clinical hematology laboratory, several terms are used to describe different aspects of Quality Assessment:
1. Accuracy (Fig. 1.6) describes how close a test result is to the true value. This term implies freedom from error. Reference samples and standards with known values are needed to check accuracy.
2. Calibration is the comparison of an instrument measurement or reading to a known physical constant.
3. Control (noun) represents a specimen that is similar in composition to the patient’s whole blood or plasma. The value of a control specimen is known. A control specimen must be carried through the entire test procedure and treated in exactly the same way as any unknown specimen; it must be affected by all the variables that affect the unknown specimen. Control specimens are tested daily or in conjunction with the unknown (patient) specimen. Controls are the best measurements of precision and may represent normal or abnormal test values.
4. Precision (Fig. 1.6) describes how close the test results are to one another when repeated analyses of the same material are performed. Precision refers to the reproducibility of test results. It is important to make a distinction between precision and accuracy. The term accuracy implies freedom from error; the term precision implies freedom from variation.
In the clinical hematology laboratory, several terms are used to describe different aspects of Quality Assessment:
1. Accuracy (Fig. 1.6) describes how close a test result is to the true value. This term implies freedom from error. Reference samples and standards with known values are needed to check accuracy.
2. Calibration is the comparison of an instrument measurement or reading to a known physical constant.
3. Control (noun) represents a specimen that is similar in composition to the patient’s whole blood or plasma. The value of a control specimen is known. A control specimen must be carried through the entire test procedure and treated in exactly the same way as any unknown specimen; it must be affected by all the variables that affect the unknown specimen. Control specimens are tested daily or in conjunction with the unknown (patient) specimen. Controls are the best measurements of precision and may represent normal or abnormal test values.
4. Precision (Fig. 1.6) describes how close the test results are to one another when repeated analyses of the same material are performed. Precision refers to the reproducibility of test results. It is important to make a distinction between precision and accuracy. The term accuracy implies freedom from error; the term precision implies freedom from variation.
5. Proficiency Testing is incorporated into the CLIA requirements with each laboratory participating in an external PT program as a means of verifi cation of laboratory accuracy. Periodically, identical samples are sent to a group of laboratories participating in the PT program; each laboratory analyzes the specimen, reports the results to the agency, and is evaluated and graded on those results in comparison to results from other laboratories. In this way, QC between laboratories is monitored. Laboratory proficiency testing is required by federal CLIA regulations.
6. Standards are highly purifi ed substances of a known composition. A standard may differ from a control in its overall composition and in the way it is handled in the test. Standards are the best way to measure accuracy. Standards are used to establish reference points in the construction of graphs (e.g., manual hemoglobin curve) or to calculate a test result.
7. QC is a process that monitors the accuracy and reproducibility of results through the use of control specimens.
Functions of a Quality Control Program
Assaying control specimens and standards along with patient specimens serves several major functions:
■ Providing a guide to the functioning of equipment, reagents, and individual technique
■ Confirming the accuracy of testing when compared with reference values
■ Detecting an increase in the frequency of both high and low minimally acceptable values (dispersion)
■ Detecting any progressive drift of values to one side of the average value for at least 3 days (trends)
■ Demonstrating an abrupt shift or change from the established average value for 3 days in a row (shift)
Assaying control specimens and standards along with patient specimens serves several major functions:
■ Providing a guide to the functioning of equipment, reagents, and individual technique
■ Confirming the accuracy of testing when compared with reference values
■ Detecting an increase in the frequency of both high and low minimally acceptable values (dispersion)
■ Detecting any progressive drift of values to one side of the average value for at least 3 days (trends)
■ Demonstrating an abrupt shift or change from the established average value for 3 days in a row (shift)
If the value of the QC specimen for a particular method is not within the predetermined acceptable range, it must be assumed that the values obtained for the unknown specimens are also incorrect, and the results are not reported. After the procedure has been reviewed for any indication of error and the error has been found and corrected, testing must be repeated until the control value falls within the acceptable range.
Analysis of Quantitative Data
It is important for hematology technologists and technicians to understand basic statistical concepts used in QC. Knowledge of specific elements of statistics is important in hematology for two reasons:
1. Application of statistical analysis of results in Quality Assessment protocols
2. Instrumental applications of statistics to erythrocyte, leukocyte, and platelet reports
It is important for hematology technologists and technicians to understand basic statistical concepts used in QC. Knowledge of specific elements of statistics is important in hematology for two reasons:
1. Application of statistical analysis of results in Quality Assessment protocols
2. Instrumental applications of statistics to erythrocyte, leukocyte, and platelet reports
Terms and Defi nitions
Average equals the sum of the test results divided by the number of tests. The average is the arithmetic mean value.
Average equals the sum of the test results divided by the number of tests. The average is the arithmetic mean value.
Mean is the term used to express the average or arithmetic mean value. The mean value is 13.6 for the following series of values: 10, 11, 14, 16, and 17.
Median is the middle value of a set of numbers arranged according to their magnitude. If two middle values exist in an even number of mathematical observations, the median is the arithmetic mean of the two middle values. The median value is 14 if the following five test values are arranged in order of size: 10, 11, 14, 16, and 17.
Mode is the term used to indicate the number or value that occurs with the greatest frequency. The mode is 45 if the following values are obtained for a control blood test: 45, 48, 35, 39, 51, 42, 45, 39, 45, 44, and 45.
Measurements of Variation
In the laboratory, measures of variation can include the range, the variance, the standard deviation, the coefficient of variation, and the z score.
Range is the term used to express the difference between the highest and lowest measurements in a series. The range is expressed in the same units as the raw data. Therefore, if the value of the raw data is expressed as a percentage (%), the range is also expressed as a percentage. If the following values are obtained, the range can be determined. The range is 0.5% to 2.0% for the following values (expressed as percentages): 1, 1.5, 1, 0.5, 2.0, 1.5, and 1.0.
Variance is an expression of the position of each observation or test result in relationship to the mean of the values. The variance is determined by examining the deviation from the mean of each individual value. If the mean value for this series of assays is 8, the variance can be determined in this
example. The following test results were obtained: 3, 4, 5, 6, 8, 9, 10, 12, and 15. The variance from the mean (deviance from the mean) of each individual result is -5, -4, -3, -2, 0, 1, 2, 4, and 7. To compute the variance, the squares of each deviation are used. The formula for computing a population variance is as follows:
example. The following test results were obtained: 3, 4, 5, 6, 8, 9, 10, 12, and 15. The variance from the mean (deviance from the mean) of each individual result is -5, -4, -3, -2, 0, 1, 2, 4, and 7. To compute the variance, the squares of each deviation are used. The formula for computing a population variance is as follows:
Standard deviation (SD) expresses the degree to which the test data tend to vary about the average value (mean). To obtain a measure of variation expressed in the same units as the raw data, the square root of the variance or the SD is used.
SD, as a measure of variability, has meaning only when two or more sets of data having the same units of measurement are compared. However, the principle of SD can be used to describe the single-set measurement.
The traditional formula for calculating the SD is the square root of the sum of all the differences from the mean squared and subsequently divided by the number of determinations (tests) minus 1. The traditional formula is as follows:
To calculate the SD of a laboratory test in the traditional manner, the following steps should be used:
1. A minimum of 20 results are needed. These results represent 20 consecutive days of testing of a control from the same pool sample.
2. Calculate the average (mean).
3. Determine the variance of each number from the mean.
4. Square each variance.
5. Add the squared variances.
6. Divide by the number of test results minus 1.
7. Find the square root of this number.
1. A minimum of 20 results are needed. These results represent 20 consecutive days of testing of a control from the same pool sample.
2. Calculate the average (mean).
3. Determine the variance of each number from the mean.
4. Square each variance.
5. Add the squared variances.
6. Divide by the number of test results minus 1.
7. Find the square root of this number.
The value obtained represents 1 SD. In many cases, the traditional formula is not appropriate because the mean does not lend itself to easy manipulation and the sum of the differences does not add up to a sum of zero. In these cases, the alternate formula, which is also the formula programmed into a scientific calculator, should be used. This formula is:
The coefficient of variation (CV), or related standard deviation, is a statistical tool used to compare variability in nonidentical data sets. The CV of each data set allows comparison of two or more test methods, laboratories, or specimen sets. To do this, the variability in each data set must be expressed as a relative rather than an absolute measure. This is accomplished for each data set by expressing the SD as a percentage of the mean. The formula for this calculation is as follows:
The z score measures how many standard deviations a particular number is from the right or left of the mean (Fig. 1.7A). A positive z score measures the number of standard deviations an observation is above the mean, and a negative z score gives the number of standard deviations an observation is below the mean. The z score is a unitless measure.
To compare the ranking of two observations from two different populations, the ranking is converted into standard units referred to as z scores or z values. The formula to compute the z score is:
Using Statistical Analysis of Results in Quality Assessment
Statistical analysis of results has been used in the clinical laboratory since the original introduction of the Levey-Jennings chart. With the advent of computer technology and computerized instrumentation in hematology, many additional systems have been introduced to monitor test results numerically. In this section, the following methods will be presented:
1. The Levey-Jennings chart
2. The cumulative sum (Cusum) method
3. Trend line analysis
4. Power functions
Statistical analysis of results has been used in the clinical laboratory since the original introduction of the Levey-Jennings chart. With the advent of computer technology and computerized instrumentation in hematology, many additional systems have been introduced to monitor test results numerically. In this section, the following methods will be presented:
1. The Levey-Jennings chart
2. The cumulative sum (Cusum) method
3. Trend line analysis
4. Power functions
The Levey-Jennings Chart
QC charts are used in the clinical laboratory to graphically display the assay values of controls versus time (e.g., day or specimen run). The Levey-Jennings chart is the traditional approach to monitoring QC (e.g., instrument calibration or lot-to-lot reagent changes).
Confidence or control limits are calculated from the mean and the SD. The confidence limits represent a set of mathematically established limits into which the majority of values (results) will fall. Within the confidence limits, the results are assumed to be accurate. It is common practice to use ±2 SD as the limit of confidence.
In the Levey-Jennings control chart (Fig. 1.8), the control results are plotted on the y-axis versus time on the x-axis. This chart shows the expected mean value by the solid line in the center and indicates the control limits or range of acceptable values by the dotted points. If the control assay value is outside the confidence limits, the control value and the patient’s values are considered to be out of control and cannot be reported. If the control assay value falls within the confidence limits, the control value and patient specimens assayed at the same time are considered to be in control, and the results can be reported.
Types of Changes
The classification of changes in a QC system is important because different kinds of changes suggest different sources. Three types of changes are commonly observed in the Levey-Jennings QC approach (Fig. 1.9):
1. Systematic drift
2. Increased dispersion of results
3. Shift or abrupt change in results
The classification of changes in a QC system is important because different kinds of changes suggest different sources. Three types of changes are commonly observed in the Levey-Jennings QC approach (Fig. 1.9):
1. Systematic drift
2. Increased dispersion of results
3. Shift or abrupt change in results
Systematic drift or trend is displayed when the control value direction moves progressively in one direction from the mean for at least 3 days. Systematic drift or a trend in control values suggests that a problem is progressively developing. This problem may be because of the deterioration of a reagent or control. Diluent contamination affects erythrocyte and leukocyte controls with an upward trend as bacterial growth increases.
Dispersion is observed when random errors or the lack of precision increases. This type of pattern indicates inconsistency in technique or a stability problem (e.g., fluctuating electrical voltage or poor mixing of a cellular control specimen).
Shift or abrupt change is observed when a problem develops suddenly. This type of change can be associated with the malfunction of an instrument or an error in technique.
Computed-Based Control Systems
Cumulative Sum (Cusum) Method. This was an early supplementary control method. Decision limits can be manually calculated from the SD with this method; however, computer systems are more efficient. This method allows for the rapid detection of trends and shifts from the mean. Its major disadvantages are that too many out of control results are obtained, and it does not readily control for random error (precision). Cusum can be used as a supplement to the Levey-Jennings system.
Cumulative Sum (Cusum) Method. This was an early supplementary control method. Decision limits can be manually calculated from the SD with this method; however, computer systems are more efficient. This method allows for the rapid detection of trends and shifts from the mean. Its major disadvantages are that too many out of control results are obtained, and it does not readily control for random error (precision). Cusum can be used as a supplement to the Levey-Jennings system.
Trend Line Analysis. Observed daily results of either the control value or the change in the SD introduced by the control value are tracked. The tracking value at each point is plotted and compared against known error limits for the control of both the mean (accuracy) and the SD (precision). If the value exceeds determined limits, a message is sent to the technologist.
Power Functions
These systems are a means of displaying the performance of a QC rule by plotting the probability for rejection versus the size of the analytical (examination) error. This computerized method can be used to determine what control rule is most useful in detecting an error of given magnitude when a specific number of controls is evaluated.
These systems are a means of displaying the performance of a QC rule by plotting the probability for rejection versus the size of the analytical (examination) error. This computerized method can be used to determine what control rule is most useful in detecting an error of given magnitude when a specific number of controls is evaluated.
Other Statistical Applications in the Hematology Laboratory
Frequency Distribution
In any large series of measurements (test results) of a normal population, the results are evenly distributed about the average value. Grouping of data in classes and determining the number of observations that fall in each of the classes is a frequency distribution of grouped data (Table 1.2).
In any large series of measurements (test results) of a normal population, the results are evenly distributed about the average value. Grouping of data in classes and determining the number of observations that fall in each of the classes is a frequency distribution of grouped data (Table 1.2).
Histogram
Information regarding frequency distribution is easier to understand if presented graphically. A bar chart provides immediate information about a set of data in a condensed form; the related pictorial representation is a histogram.
Information regarding frequency distribution is easier to understand if presented graphically. A bar chart provides immediate information about a set of data in a condensed form; the related pictorial representation is a histogram.
Histograms can have almost any shape or form. The most frequently encountered type of distribution is the bell-shaped histogram, which is symmetrical. The bell shape may vary, with some curves being flatter and wider than others; however, most values cluster about the mean, with a few values falling in the extreme tails of the curve. This normal curve is referred to as a Gaussian distribution (see Fig. 1.7B).
In the bell-shaped normal curve, ±1 SD includes 68% of all of the values, ±2 SD includes 95% of the values, and ±3 SD includes 99.7% of the values. For biological studies, control confidence limits are usually established at ±2 SD. When values fall outside these limits, the procedure is considered out of control. In the establishment of reference values for a procedure, the reference range for a specific assay refl ects the statistical processing of a large number of normal samples and represents the values found within 2 or 3 SDs.
In Chapter 27, histogram data generated by automated cell-counting systems are presented. The interpretation of patient histograms compared with histograms based on established normal values for erythrocytes, leukocytes, and platelets are presented in detail.
CHAPTER HIGHLIGHTS
Hematology is the discipline that studies the development and diseases of blood. Basic procedures performed in the hematology laboratory include the CBC. Molecular diagnostics, flow cell cytometry, and digital imaging are modern techniques that have revolutionized the laboratory diagnosis and monitoring of many blood disorders. The field of hematology encompasses the study of blood coagulation––hemostasis and thrombosis.
Hematology is the discipline that studies the development and diseases of blood. Basic procedures performed in the hematology laboratory include the CBC. Molecular diagnostics, flow cell cytometry, and digital imaging are modern techniques that have revolutionized the laboratory diagnosis and monitoring of many blood disorders. The field of hematology encompasses the study of blood coagulation––hemostasis and thrombosis.
Medical laboratory professionals in the hematology laboratory and phlebotomists who are on the front lines play a major role in patient care. Although the CBC is the most frequently requested procedure, a laboratorian must be familiar with the theory and practice of a wide variety of automated
and manual tests performed in the laboratory to provide quality patient care.
Safety in the Hematology Laboratory
The practice of safety should be uppermost in the mind of all persons working in a clinical hematology laboratory. Most laboratory accidents are preventable by exercising good technique, staying alert, and using common sense. One of the goals of particular interest to laboratory professionals addresses the issue of critical laboratory assay values because urgent notification of critical results to the primary healthcare provider is the responsibility of the laboratory.
The practice of safety should be uppermost in the mind of all persons working in a clinical hematology laboratory. Most laboratory accidents are preventable by exercising good technique, staying alert, and using common sense. One of the goals of particular interest to laboratory professionals addresses the issue of critical laboratory assay values because urgent notification of critical results to the primary healthcare provider is the responsibility of the laboratory.
A designated safety officer is a critical part of a laboratory safety program. OSHA Acts and Standards ensure that workers have safe and healthful working conditions. The “Right to Know” laws and the OSHA-mandated Occupational Exposure to Bloodborne Pathogens regulation require that laboratories develop, implement, and comply with a plan that ensures the protective safety of laboratory staff to potential infectious bloodborne pathogens, HBV and HIV. The law further specifies the rules for managing and handling medical waste in a safe and effective manner.
Blood is the most frequently implicated infected body fluid in HIV and HBV exposure in the workplace. An occupational exposure is defined as a percutaneous injury, for example, needlestick or cut with a sharp object, or contact by mucous membranes or nonintact skin, or the contact is prolonged or involves an extensive area with blood, tissues, blood-stained body fluids, body fluids to which standard precautions apply, or concentrated virus. The most widespread control measure required by OSHA and CLSI is the use of puncture-resistant sharps containers. An occupational exposure should be considered to be an urgent medical concern to ensure timely postexposure management. After skin or mucosal exposure to blood, the ACIP recommends immunoprophylaxis, depending on several factors.
Safe Work Practices and Protective Techniques for Infection Control
Each laboratory must have an up-to-date safety manual. This manual contains a comprehensive listing of approved policies, acceptable practices, and precautions including standard precautions. Standard precautions represent an approach to infection control used to prevent occupational exposures to bloodborne pathogens.
Each laboratory must have an up-to-date safety manual. This manual contains a comprehensive listing of approved policies, acceptable practices, and precautions including standard precautions. Standard precautions represent an approach to infection control used to prevent occupational exposures to bloodborne pathogens.
Gloves should be used as an adjunct to, not a substitute for, handwashing. All work surfaces are cleaned and sanitized at the beginning and end of the shift with a 1:10 dilution of household bleach or an EPA-registered disinfectant. A variety of other safety practices should be adhered to, to reduce the risk of inadvertent contamination with blood or certain body fluids. Protective gloves should always be worn for handling any type of biological specimen.
Quality Assessment in the Hematology Laboratory
The assessment of quality results for the various analyses is critical and is an important component of the operation of a high-quality laboratory. Quality assessment is used in the clinical hematology laboratory to ensure excellence in performance. A systematic approach to quality assures that correct laboratory results are obtained in the shortest possible time and at a reasonable cost. A quality assessment system is divided into two major components: nonanalytical factors and the analysis of quantitative data (QC). Nonanalytical factors that support quality testing include qualified personnel, laboratory policies, laboratory procedure manual, test requisitioning, patient identification, and specimen procurement and labeling; specimen collection, transport, and processing and storage; and preventive maintenance of equipment, appropriate methodology, and accuracy in reporting results and documentation. Delta checks are particularly important to rule out mislabeling, clerical error, or possible an analytical (examination) error.
The assessment of quality results for the various analyses is critical and is an important component of the operation of a high-quality laboratory. Quality assessment is used in the clinical hematology laboratory to ensure excellence in performance. A systematic approach to quality assures that correct laboratory results are obtained in the shortest possible time and at a reasonable cost. A quality assessment system is divided into two major components: nonanalytical factors and the analysis of quantitative data (QC). Nonanalytical factors that support quality testing include qualified personnel, laboratory policies, laboratory procedure manual, test requisitioning, patient identification, and specimen procurement and labeling; specimen collection, transport, and processing and storage; and preventive maintenance of equipment, appropriate methodology, and accuracy in reporting results and documentation. Delta checks are particularly important to rule out mislabeling, clerical error, or possible an analytical (examination) error.
Quality Control in the Hematology Laboratory
QC monitors the accuracy and precision of test performance over time. The purpose of QC is to detect errors that result from test system failure, adverse environmental conditions, and variance.
It is important for hematology technologists and technicians to understand basic statistical concepts used in QC. Knowledge of specific elements of statistics is important in hematology in order to apply statistical analysis of results and in instrumental applications of statistics to erythrocyte, leukocyte, and platelet reports.
Statistical analysis of results has been used in the clinical laboratory since the original introduction of the Levey-Jennings chart. With the advent of computer technology and computerized instrumentation in hematology, many additional systems have been introduced to monitor test results numerically.
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Reference: Clinical Hematology 5 Edition - Mary Louise Turgeon
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