Quality Assurance and Quality Control

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Quality Assurance and Quality Control

Learning Objectives

At the conclusion of this chapter, the reader should be able to:

• Identify the regulatory and accrediting organizations that influence quality assessment in clinical laboratories.

• Describe the eight nonanalytical factors related to testing accuracy.

• Identify and give examples of the three categories of errors related to the phase of testing.

• Define the terms accuracy, precision, reproducibility, and reliability.

• Describe the use of the coefficient of variation and give the formula.

• Define true positive, true negative, false positive, and false negative.

• Provide the equations for calculating percentage sensitivity and percentage specificity.

• Define positive predictive value and negative predictive value.

• Describe the process of proficiency testing.

• Explain the use of control specimens.

• Cite seven causes for a control value being out of the acceptable range or out of control.

• Define the terms mean, median, mode, standard deviation, and reference range.

• Discuss issues related to testing outcomes.

• Describe parallel testing of test kits.

• Describe how a new procedure is validated.

• Write and evaluate a procedural write-up using CLSI requirements.

• Correctly answer case study–related multiple choice questions.

• Be prepared to participate in a discussion of critical thinking questions.

• Correctly answer end of chapter review questions.

Key Terms

The introduction of routine quality assurance (QA) programs and quality control (QC) in the clinical laboratory was a major advance in improving the accuracy and reliability of testing. This process ensures the clinician ordering the test that the testing method has been done in the best possible way to provide the most useful information in diagnosing or managing a patient. QA indicators and QC are tools to ensure that reported laboratory results are of the highest quality.

Clinical Laboratory Regulatory and Accrediting Organizations

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 Qualification, was published in the Federal Register in January 2003. Enactment of the CLIA established a minimum threshold for all aspects of clinical laboratory testing.

Voluntary standards have been set by The Joint Commission (TJC), the Commission on Office Laboratory Accreditation (COLA), and the College of American Pathologists (CAP).

A more recent development in voluntary accreditation aimed at improving quality was the introduction of ISO 15189. The International Organization for Standardization (ISO) is the world’s largest nongovernmental developer and publisher of international standards. ISO standards and certification are widely used by industry, but ISO 15189 has now been formulated for clinical laboratories. ISO 15189 has gained some standing abroad as a mandatory accreditation, such as in Australia, Ontario, and many European countries. In the United States, ISO 15189 accreditation remains optional. Requirements for quality and competence in ISO 15189 are unique because it takes into consideration the specific requirements of the medical environment and the importance of the medical laboratory to patient care. CAP 15189 is a voluntary nonregulated accreditation to the ISO 15189:2007 standard as published by ISO. CAP 15189 does not replace CAP’s CLIA-based Laboratory Accreditation Program, but complements CAP accreditation and other quality systems by optimizing processes to improve patient care, strengthen the deployment of quality standard, reduce errors and risk, and control costs.

Nonanalytical Factors Related To Testing Accuracy

Qualified Personnel

The competence of personnel is an important determinant of the quality of the laboratory result. Only properly certified personnel can perform nonwaived assays (see Chapter 9 for levels of laboratory testing).

Laboratory Procedure Manual

A complete laboratory procedure manual for all analytical procedures performed in the laboratory must be provided. The manual must be reviewed regularly, in some cases annually, by the supervisory staff and updated as needed.

A complete laboratory procedure manual for all procedures performed in the laboratory must be provided. The Clinical and Laboratory Standards Institute (CLSI) recommends that these manuals follow a specific pattern for how procedures are organized (Box 7-1).

Box 7-1   Written Procedural Protocol

Adapted from Clinical and Laboratory Standards Institute: Clinical laboratory technical procedure manual: approved guideline, ed 4, Wayne, Pa, 2002, CLSI Document GP2-A4.

Inaccurate Results

Inaccuracies in testing can be systematic or sporadic. Systematic errors can be eliminated by a program that monitors equipment, reagents, and other supplies. Sporadic or isolated errors in technique can produce false-positive and false-negative results, depending on the technique used for testing (Box 7-2).

Box 7-2   Possible Causes of Technical Errors

False-Positive Errors

Overcentrifugation of serum cell mixture

Dirty glassware

Hemolyzed patient serum

Inadequate dispersal of centrifuged serum cell mixture

Extended incubation

An important aspect of quality is documentation of results. CLIA regulations mandate that any problem or situation that might affect the outcome of a test result be recorded and reported. These incidents can involve specimens that are improperly collected, labeled, or transported to the laboratory or problems concerning prolonged turnaround times for test results. There must be a reasonable attempt to correct the problems or situation and all steps in this process must be documented.

Errors Related to Phase of Testing

The Institute for Quality Laboratory Medicine has developed measures to evaluate quality in the laboratory based on the preanalytical, analytical, and postanalytical phases of testing.

Errors occurring during the analytical phase of testing in clinical laboratories are now relatively rare. Currently, most laboratory errors are related to the preanalytical and postanalytical phases of testing. To guarantee the highest quality laboratory results and to comply with CLIA regulations, various preanalytical factors need to be considered (Boxes 7-3 and 7-4).

Box 7-3   Preanalytical Errors

Incorrect test request

Specimen obtained from wrong patient

Specimen procured at wrong time

Specimen collected in wrong tube or container

Blood specimens collected in wrong order

Incorrect labeling of specimen

Improper processing of specimen

Box 7-4   Postanalytical Errors

Recording results inaccurately

Verbally reporting results for wrong patient

Quality Descriptors

Quality control 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 procedure and any corrective action taken in response to these problems. All solutions and kits used in testing must be carefully checked before actually being used for testing patient samples.

Definitions

Quality control consists of procedures used to detect errors that result from test system failure, adverse environmental conditions, and differences between technologists, as well as the monitoring of the accuracy and precision of test performance over time. Accrediting agencies require monitoring and documentation of quality assessment records. Documentation of QC includes preventive maintenance records, temperature charts, and QC charts for specific assays.

Quality control monitors the accuracy and reproducibility of results through the use of control specimens. The diagnostic usefulness of a test and its procedure is assessed by using statistical evaluations, such as descriptions of the accuracy and reliability of the test and its methodology.

The terms accuracy and precision are often used to describe quality. Accuracy describes how close a test result is to the true value. Precision describes how close the test results are to one another when repeated analyses of the same specimen are performed. It is possible to achieve great precision, with all laboratory personnel who perform the same procedure arriving at the same answer, but without accuracy if the answer does not represent the actual value being tested. Accuracy can be improved by the following:

• Use of properly standardized procedures

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