Verification of method performance for clinical laboratories

Method verification, a one-time process to determine performance characteristics before a test system is utilized for patient testing, is often confused with method validation, establishing the performance of a new diagnostic tool such as an internally developed or modified method. A number of international quality standards (International Organization for Standardization (ISO) and Clinical Laboratory Standards Institute (CLSI)), accreditation agency guidelines (College of American Pathologists (CAP), Joint Commission, U.K. Clinical Pathology Accreditation (CPA)), and regional laws (Clinical Laboratory Improvement Amendments of 1988 (CLIA'88)) exist describing the requirements for method verification and validation. Consumers of marketed test kits should verify method accuracy, precision, analytic measurement range, and the appropriateness of reference intervals to the institution's patient population. More extensive validation may be required for new methods and those manufacturer methods that have been modified by the laboratory, including analytic sensitivity and specificity. This manuscript compares the various recommendations for method verification and discusses the CLSI evaluation protocols (EP) that are available to guide laboratories in performing method verification experiments.