Comparison of Human Chorionic Gonadotropin Measurements by Radioimmunoassay and In Vitro Bioassay

Publisher Website
Google Scholar
Abstract
A sensitive, accurate, and reproducible in vitro bioassay was developed for measuring human chorionic gonadotropin (hCG), based on testosterone production by collagenase-dispersed interstitial cells of rat testes in repsonse to hCG. The results were compared to those obtained by established beta hCG radioimmunoassay. The assay sensitivity was 25 pg hCG-CR119/ml (65 .mu.IU second IRP/ml). The intra-assay coefficient of variation (CV) was 8.8%, and the interassay CV was 13% and 33% in the high and low ranges of the standard curve, respectively. hCG recoveries were 89.6 .+-. 3.12% (SE, n = 12). The pattern of serum bio-hCG followed established patterns of immuno-hCG, with the highest level measured during the first trimester mean, 52,6000 .+-. 7,250 SE (mIU/ml, n = 11), decreasing thereafter to a mean value of 7,400 .+-. 1,500 mIU/ml at term. The mean ratio of the bio/immunoactivity was consistently greater than one and did not significntly change at the vairous stages of pregnancy, or between normal and molar pregnancies (first trimester, 1.75 .+-. 0.12 SE; mid-trimester, 1.46 .+-. 0.12; term, 1.50 .+-. 0.09; molar, 1.55 .+-. 0.2). When serum bioactive and immunoactive hCG were measured in a woman at five weeks of pregnancy, an episodic secretion of hCG was obained by both assays.