Calibration Verification and Linearity (CVL) Program

As specified in the CAP LAP Chemistry and Toxicology Checklist, laboratories are required to verify the AMR at least every six months, or if changes are made to an assay without recalibration. If your laboratory performs calibrations or calibration verification at least every six months using material that spans the low, mid, and high range of the AMR, separate AMR verification is not required. Coagulation tests based on direct measurement of an analyte require AMR verification at least every six months according to the LAP Hematology and Coagulation Checklist.

If your laboratory performs calibrations at least every six months, current CLIA regulations and the CAP Laboratory Accreditation Program do not require separate calibration verification. Otherwise, laboratories are required to confirm calibration verification at least every six months, or if changes are made to an assay without recalibration.

If your evaluation is Nonlinear, but your results are similar to your peer group, the nonlinearity may be inherent in the method and it is not specific to your instrument. The same scenario may occur due to a nonlinear matrix effect in the Survey material. In this case, it may be useful to investigate the apparent nonlinearity with previously tested patient specimens to identify a possible matrix effect. If your CAP calibration verification evaluation results include low, midpoint, and high values and the evaluation criteria are acceptable to your laboratory, your AMR is verified.

Make sure you are reporting in the correct units of measure and have not made a decimal place error. If your results are in agreement for some specimens, look for evidence of a peer-level problem. The peer group means may be influenced by laboratories that are nonlinear due to instrument differences or because of aging reagents. In this case, the coefficients of variation (CV) for the higher specimens tend to be much larger than the CVs of the midrange specimens. If your evaluation is Linear and there is evidence that the mean of your peer group includes nonlinear results, you should note that you suspect a peer-level problem.

The LAP Chemistry and Toxicology Checklist requires both calibration verification and AMR verification. You can use successful performance in the CVL Surveys to verify your AMR, but you must confirm that the evaluation includes specimens near the low, midpoint, and high values of the AMR. The LAP Hematology and Coagulation Checklist states that coagulation tests based on direct measurement of an analyte require AMR verification. Calibrated tests that directly measure activity or concentration of an analyte by enzyme immunoassay, immunoturbidity, or chromogenic methods require AMR verification. Clot-based tests do not require AMR verification. The checklist also states that linearity studies are not required for calibration and calibration verification of CBC instruments.

For the majority of the CVL Surveys, we offer the expedited linearity evaluation service, which provides your linearity evaluation via e-LAB Solutions within two business days of receipt of your data. Results may be submitted by any method, but they must be received by the due date printed on your result form. The expedited linearity evaluation provides the opportunity to verify your submitted results, review your linearity evaluation, and submit any necessary data corrections prior to the start of the CVL Survey processing. If data revisions are submitted prior to the survey due date, we will generate another expedited linearity evaluation. Your complete report package, including the calibration verification evaluation, will be generated after the survey due date when the peer summary results can be calculated.

We always use data from the current mailing to calculate peer-based target values and peer group summary statistics. We strive to include as much data as possible, especially for smaller peer groups. We believe this provides the most accurate peer group information for evaluations that utilize peer-based target values. Once we have begun summarizing the peer group data, it takes several days to generate and review the evaluation reports. We spend additional time formatting the Participant Summary reports, which may include commentary by Instrumentation Resource Committee members. Please note that you will have faster access to your full evaluation report package with e-LAB Solutions.