AlphaLISA for the determination of median levels of the free ß subunit of human chorionic gonadotropin in the serum of pregnant women.

ABSTRACT

Measurement of the free ß subunit of human chorionic gonadotropin (free ß-hCG) in serum is useful for prenatal screening. Concentrations of free ß-hCG vary in different races. Conventional assays used for such measurements have limitations. We applied the AlphaLISA to measure levels of free ß-hCG in maternal serum during 8-20 weeks of gestation in women from southern China. Two anti-free ß-hCG antibodies were used one was coated on AlphaLISA acceptor beads and the one was biotinylated. The assay also contained donor beads coated with streptavidin. The AlphaLISA assay detection limit was 0.11 ng/mL, and the analytical range was 0.11-200 ng/mL. The intra- and interassay coefficients of variation were 1.32%-2.50% and 3.44%-5.45%, respectively. The correlation with commercial Eu(3+)-labeled free ß-HCG-TRFIA assay was good (y = 1.045x + 1.580, r(2) = 0.978). Median levels of free ß-hCG in maternal serum at 8-20 weeks gestation were higher in women from southern China compared with those reported in women from other countries. The AlphaLISA for free ß-HCG could become the assay of choice for applications in clinical diagnostics. The established median value of free ß-HCG is helpful in clinical diagnosis specific for southern Chinese women.