Quantitative, wide-range, 5-minute point-of-care immunoassay for total human chorionic gonadotropin in whole blood

Abstract

Background: Human chorionic gonadotropin (hCG) is among the most common analytes available for point-of-care immunotesting, with most assays currently based on simple manual assay devices. However, as the importance of good analytical performance of rapid assays is increasingly emphasized, more sophisticated immunoassay techniques are needed to meet the future challenges of rapid yet quantitative POC testing. Methods: We developed a simple, dry-reagent, all-in-one immunoassay for the quantitative measurement of hCG in whole blood, plasma, or serum. The noncompetitive assay equally measures intact, nicked, and hyperglycosylated hCG as well as nonnicked and nicked hCG β-subunit with a rapid and simple procedure consisting of a 5-min, one-step incubation and, subsequent to washing, the measurement of time-resolved fluorescence directly from a wet well surface. Results: The assay had a detection limit (background + 3 SD) of 0.4 IU/L hCG. The within-run CV was <15% down to 2 IU/L, and the assay was linear to 6000 IU/L. The within- and between-run CVs in heparinized whole blood and plasma were ≤10% throughout the measured range (4.0-4400 IU/L). The mean (95% confidence interval) difference between whole blood and plasma was -42 (-24 to -61)% without hematocrit correction and 6.5 (-14 to 27)% with hematocrit correction (n = 106). Regression analysis with the Diagnostic Products IMMULITE® 2000 hCG method yielded the following: slope (SD), 1.02 (0.01); y-intercept (SD), -6 (10) IU/L; Sy|x = 99 IU/L (n = 124; range, 1.6-4746 IU/L; r = 0.995). Conclusions: Combined with the fully automated instrumentation, the 5-min, dry-reagent assay allows quantitative and reproducible determination of hCG in whole blood while sustaining the speed and simplicity of conventional rapid assays. © 2004 American Association for Clinical Chemistry.