College of American Pathologists
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March 2003

CLIA ’88 regulations use the term "calibration verification" to refer to the verification of correct method calibration and validation of the AMR. The CAP’s checklists use separate terms, as follows, to identify two distinct processes required for good laboratory practice.

Analytical measurement range validation:

The process of confirming that the assay system will correctly recover the concentration or activity of the analyte over the AMR. The materials used for validation must be known to have matrix characteristics appropriate for the method. The matrix of the sample-that is, the environment in which the sample is suspended or dissolved-may influence the measurement of the analyte. In many cases, the method manufacturer will recommend suitable materials. The test specimens must have analyte values that, at a minimum, are near the low, midpoint, and high values of the AMR. Specimen target values can be established by comparison with peer group values for reference materials, by assignment of reference or comparative method values, and by dilution or admixture ratios of one or more specimens with known values. Each laboratory must define limits for accepting or rejecting validation tests of the AMR. The AMR must be revalidated at least every six months, at changes in major system components, and when a complete change in reagents for a procedure is introduced, unless the lab can demonstrate that changing reagent lot numbers does not affect the range used to report patient/client test results. Routine reagent lot changes may not require AMR revalidation if they occur within the six-month interval. The laboratory director should determine what constitutes a major system component change or a "complete" change in reagents that would require revalidation of the AMR. Manufacturers’ instructions should be followed.

Calibration verification:
The process of confirming that the current calibration settings remain valid for a method. If calibration verification confirms that the current calibration settings are valid, it is not necessary to perform a complete calibration or recalibration of the method. Calibration verification can be accomplished in several ways. If the method manufacturer provides a calibration validation or verification process, it should be followed. Other techniques include (1) assay of the current method calibration materials as unknown specimens and determination that the correct target values are recovered, and (2) assay of matrix-appropriate materials with accurate target values that are specific for the method. Materials for calibration verification must have a matrix appropriate for the clinical specimens assayed by that method and target values appropriate for the measurement system. In general, routine control materials are not suitable for calibration verification, except in situations where the material is specifically designated by the method manufacturer as suitable for verification of the method’s calibration process.