Assurance of Laboratory Testing Quality

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Accurate laboratory testing is essential to public health. Yet no laboratory test can be guaranteed to be accurate 100 percent of the time. In order to assure that test results are acceptable and reliable, a laboratory must incorporate both quality assurance and quality control procedures into its daily laboratory routine.

Quality assurance is the ongoing process of monitoring laboratory procedures so that corrective action can be taken when established criteria are not met. A critical element is the monitoring of the sample or specimen collection procedure. This includes making sure that the appropriate sample is submitted within the timeframe required, that it is shipped or carried to the laboratory under correct conditions for accurate testing, and that it is stored and handled according to the test protocol developed within the laboratory. A vital part of quality assurance is the statistical monitoring of the specific procedures used to measure quality control within the laboratory. Quality assurance includes both qualitative and quantitative parameters beginning with the conditions under which the specimen is collected and concluding with final report and disposition of the specimen following testing. Quality control consists of only those parameters that can be measured and reported statistically.

Internal quality control procedures can include recording the temperatures of refrigerators, freezers, incubators, water baths, and rooms; inclusion of positive and negative controls with each type of test performed; and documentation of the lot numbers and expiration dates of every reagent or medium used in testing. These procedures must be monitored routinely to alert the analyst to situations that may result in the unsatisfactory performance of a test. Corrective action can then be taken before any erroneous results are reported. External quality control, using anonymous and coded performance evaluation samples, is used to aid a laboratory in assessing its results and provide laboratory-to-laboratory comparisons.

Kathleen L. Meckstroth

(see also: Diagnostic Testing for Communicable Disease; Laboratory Services; Laboratory Technician; Practice Standards; Reference Laboratory )