Analytic Evaluation of the ??-Human Chorionic Gonadotropin Assay on the Stratus CS and Its Use in POCT

Abstract

The authors assessed the analytic performance of the Stratus CS (Dade Behring) β-human chorionic gonadotropin (βhCG) assay for quantitative measurement of intact hCG and β-subunit of hCG, and the possible use of this test in point-of-care testing (POCT). Commercial control samples and plasma pools were used to determine the calibration curve stability, precision, detection limit, and linearity, and stability of samples and reagents at room temperature. To assess the agreement between the Stratus CS βhCG and Dimension RxL hCG assays, a series of consecutive samples, recruited from outpatients (nonpregnant women) and from patients in the obstetric ward, were used. The total imprecision was 3.5 to 4.2% for concentrations ranging from 9.0 to 3370 IU/L βhCG. The detection limit was 0.39 IU/L. The assay was linear up to 950 IU/L. Sample and reagent stability studies showed a nonsignificant effect of room temperature. The comparison between Stratus CS βhCG and Dimension RxL hCG showed agreement when the determinations were evaluated inside the linearity of the βhCG assay (0-1250 IU/L; bias, −3.474). The bias measurement was found to be unsatisfactory when the determinations were evaluated on the homogeneous sample groups (pregnancy, spontaneous abortions, and ectopic pregnancy). The Stratus CS βhCG test is a fast, precise, and sensitive method for the determination of hCG and βhCG, and can thus be used in the routine or stat laboratory workups. This comparison study confirms that accurate utilization of POCT in the emergency department, and optimal integration between POCT and the core laboratory for hCG methods requires a methodological standardization of assays.