Q&A column

Q. Does the CAP require instrument-to-instrument comparability studies at least twice a year for waived point-of-care testing instruments, such as glucose meters, or nonwaived instruments, such as critical care analyzers? Are we required to perform a linearity study twice a year on all waived and nonwaived POC testing instruments?

A.Per CAP checklist requirement COM.04250 Comparability of Instruments and Methods—Nonwaived Testing, all nonwaived methods and instruments, including nonwaived POC testing instruments, need to be checked against each other at least twice a year for comparability of results. The laboratory may use a control product or patient sample for the studies. If the main laboratory and POC testing areas are under the same CAP number, at least one of the nonwaived POC testing instruments must be compared with the main laboratory instruments that report the same analyte. The remaining nonwaived POC instruments can then be compared to the POC instrument that was compared to the main laboratory instruments.

The CAP does not require instrument-to-instrument comparisons for waived testing as long as the laboratory follows all of the manufacturer’s instructions as defined for the test system and has not modified the test.

The CAP does not mandate that laboratories perform linearity studies on nonwaived POC testing instruments. However, they must verify the analytical measurement range for such instruments at least every six months following defined criteria. While linearity materials can be used for such purposes, the POC testing checklist requirement POC.08500 AMR Verification Materials describes other suitable materials as well. Furthermore, POC.08600 AMR Verification contains information on an alternative process in which the analytical measurement range can be verified on a sampling of devices when a large number of single-use devices are in use.

For waived testing, laboratories are required to follow the manufacturer’s instructions for calibration, calibration verification, and related processes. Manufacturer instructions that require performing linearity studies at a defined frequency must also be followed.

Shelley Martire, MLS(ASCP)^CM
LAP Senior Technical Specialist
College of American Pathologists
Northfield, Ill.