Two-center clinical evaluation of a new automated fluorometric immunoassay for the quantitative analysis of total betaeta-human chorionic gonadotropin.

Objectives: This study evaluated the quantitative total betahCG assay on the Stratus CS point-of-care instrument at two medical centers.

Design And Methods: Analytical sensitivity, linearity, within-run and total imprecision, interferences, dilution recovery, method comparison (Dimension RxL), comparison of matched heparinized whole blood and plasma samples, and determination of the normal reference interval were studied.

Results: Analytical sensitivity was <0.5 IU/L. The assay's linear range was 0 to 1250 IU/L; the clinical reportable range was up to 50,000 IU/L. Within-run imprecision (CV) at both low (<20 IU/L) and elevated (760 IU/L) betahCG concentrations were <4%. Total imprecision for three QC levels and two pools were <4%. Method comparison showed Stratus CS betahCG = 0.98 +/- 0.01* Dimension RxL hCG -0.11 +/- 2.69 (n = 136; r = 0.996; Sy/x = 27.7). Matched heparinized whole blood/plasma sample-comparison showed: whole blood = 1.05*Plasma + 0.37 +/- 1.29 (n = 41; r = 1.000; Sy/x = 7.57). Mean dilution recovery was 99% (range: 95% to 103%). None of the 52 drugs tested, lipemia, icterus, hemolysis, LH, FSH, TSH, hGH or prolactin represented a significant interference with the assay. Reference intervals were <0.5 IU/L for males (n = 123) and <3.0 IU/L for nonpregnant females (n = 120).

Conclusions: The Stratus CS betahCG test offers the advantage of quantitative measurement of total betahCG in whole blood at the point of care and is suitable for clinical use.