Analytical performance evaluation of the i-STAT Total β-human chorionic gonadotropin immunoassay

Background: The ability to perform quantitative hCG testing in whole blood at the point-of-care is desirable. The purpose of this study was to perform an analytical validation of the Abbott i-STAT Total β-hCG test. Methods: Whole blood, plasma, and serum samples were prepared by the addition of hCG and were used to evaluate precision, linearity, analytical sensitivity, accuracy, the high-dose hook effect, and dilution recovery. Results: Imprecision was highest with whole blood (CV=16.0% and 6.7% at 10 and 1184IU/l, respectively) and lowest in serum (CV=8.1% and 4.3% at 11 and 1305IU/l, respectively). The limits-of-quantitation were 8 and <5IU/l for whole blood and both plasma and serum, respectively. The assay was linear between 5 and 2000IU/l in all sample types (R²≥0.998). i-STAT results agreed most closely with the Architect Total β-hCG assay and with greater differences observed with Beckman DxI Total βhCG and Roche Cobas e601 hCG+β assays (mean differences across all sample types were 9.3% and 12.3%, respectively). A high-dose hook effect was observed at concentrations >400,000IU/l. Accuracy was achieved in samples diluted with serum but not saline. Conclusions: The i-STAT Total β-hCG test demonstrates acceptable performance for quantifying hCG in whole blood, plasma and serum.