Challenges in harmonizing integrated healthcare network laboratories: multi-center evaluation of the hCG5 assay.

Background: Beckman Coulter recently introduced a new hCG assay manufactured for the Access 2 and DxI platforms. This assay is the first to use the 5th International Standard (5th IS) as its primary calibration material. Clinical laboratories are required to validate the method performance before testing and reporting patient results.

Methods: Beckman Coulter Access 2 instruments (n=41) across Kaiser Permanente Northern California were evaluated for their performance characteristics using the hCG5 reagent. Precision, linearity, dilution verification, and patient sample comparisons were performed on each instrument.

Results: The assay was linear up to 1350IU/L. Intra-day and inter-day precision ranged from 1.0%-3.3% and 1.8-7.3%, respectively, for the low QC material (mean concentration 4.6IU/L). Percent bias between the previous assay (hCG2) and the hCG5 assay was 3.2 to 22.7% for hCG concentrations <1000IU/L and -2.9 to 30% for concentrations >1000IU/L. On board and manual dilutions agreed within 15% following proper adjustment of the instrument dilution factor.

Conclusions: Achieving Access 2 inter-instrument agreement on specimens needing dilutions (hCG>1350IU/L) requires validation of the on board dilution factor. Laboratories should use QC material above the linear range to monitor instrument dilution accuracy and precision.