College of American Pathologists Quality Cross Check -Chemistry and Therapeutic Drug Monitoring as a tool for biannual instrument correlations.

Background: Biannual instrument-correlation studies are required for nonwaived assays performed on multiple instruments.

Objective: To determine the feasibility of using College of American Pathologists (CAP) Quality Cross Check-Chemistry and Therapeutic Drug Monitoring (CZQ) to assess instrument correlations among multiple analyzers, analyzer models, and Clinical Laboratory Improvement Amendments (CLIA) licenses for 55 unique analytes.

Methods: Instrument correlation studies were performed on 9 Abbott ARCHITECT instruments (c4000 [n = 4], c8000 [n = 2], and c16000 [n = 3]) over 3 CLIA licenses using CZQ materials. The mean (SD) values, concentration difference, percent bias, and peer data for each individual level of CZQ were determined for each individual analyzer. Acceptable concentration and percentage for each analyte were set using criteria from CAP or other reputable sources such as the American Association of Bioanalysts or the Royal College of Pathologists of Australasia. Peer data were provided by CAP with the CZQ kit.

Results: Correlations using CZQ materials showed that 94.5% of assays studied were within the acceptability criteria by percent bias only and 98.2% were within acceptability criteria by concentration difference.

Conclusions: The use of CZQ provides support to standardized correlation studies among instruments within and across separate CLIA licenses. However, widespread adoption of CZQ may be limited due to concerns regarding matrix effects, analyte ranges, and ease of data analysis.