Comparability of four clinical laboratory measurement methods for GGT and commutability of candidate reference materials.

BACKGROUND: This study was conducted to evaluate the progress in the standardization of the gamma-glutamyl transferase (GGT) to achieve metrological traceability of routine in vitro diagnosis (IVD) medical devices.
METHODS: We collected 25 single fresh frozen serum samples for GGT analysis. Candidate reference materials (RMs), calibrators, internal quality controls (IQC), and external quality assessment (EQA) materials from the National Center for Clinical Laboratory (NCCL), Beijing Center for Clinical Laboratory (BCCL), and College of American Pathologists (CAP) were randomly added to these serum samples. A total of 42 samples were examined using IFCC reference method and four different IVD medical devices to perform the comparability and commutability study.
RESULTS: The four IVD medical devices achieved trueness assessment within the measurement range. Linear analysis showed the agreement of Siemens ADVIA 2400, Hitachi 7600-020/BioSino, Beckman AU 5800, and Roche Cobas 501 with the reference method. These assay pairs were comparable at the medical decision levels. The GGT in-house candidate RMs, and Beckmann and Roche calibrators were all within the limits of the 95% prediction intervals, the commutability of BioSino calibrators was indeterminate, and some internal and external quality controls were not commutable for comparisons of certain IVD medical devices vs the reference method.
CONCLUSIONS: By comparing with the reference method, we found that performance of GGT conventional measurement systems to be traceable to the higher order references was improved. The commutable materials for calibration and trueness controls of routine methods were significant to promote the standardization of GGT analysis.