[Fundamental evaluation of ELSA.F-beta HCG kit as an immunoradiometric assay specific for serum beta HCG]

We evaluated ELSA.F-beta HCG kit as an immunoradiometric assay (IRMA) specific for serum beta human chorionic gonadotropin (beta hCG). This IRMA was found to be highly sensitive to serum beta hCG; the minimum detectable concentration of beta hCG was 0.05 ng/ml. No significant effects on the standard curves were observed when first and second incubation time and temperature were varied from 30 min to 240 min and from 4 degrees C to 37 degrees C, respectively. Commercial LH, FSH, and TSH had little effect on the assay system; the cross-reactivity of commercial hCG was 2.5%, and 0.14% after unconjugated beta hCG with alpha-subunit was absorbed with ELSA-tube. Multiple dilutions of sera of pregnancy resulted in curves paralleling that obtained using standard beta hCG; the recovery of beta hCG added to the serum was 98.1 +/- 2.5% (mean +/- SD), and mean coefficient of variation of the interassay reproducibility of serum beta hCG (n = 10) was 6.7 +/- 2.8 (SD)%. Serum beta hCG concentration measured using ELSA.F-beta HCG kit was well correlated with that measured using conventional beta hCG RIA kit (r = +0.961, p less than 0.01), although values were lower than those measured with the latter (y = 0.35x + 0.26). Our results suggest that ELSA.F-beta HCG kit is a useful assay system for serum beta hCG.