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

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 response to hCG. The results were compared to those obtained by established beta hCG radioimmunoassay. The assay sensitivity was 25 pg hCG-CR119/ml (65 μIU 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, 52,600 ± 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 significantly change at the various 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 obtained by both assays.     

Power of a simplified multivariate test for genetic linkage

In this paper we compare the power of the multivariate Haseman–Elston (MHE) test proposed earlier by Amos et al . (1990) and a computationally rapid new version of the multivariate Haseman–Elston test (NMHE) (Elston et al . 2000). We show that the power of NMHE was, for different simulation setups, identical or higher than that of MHE. In the bivariate case, the power of the NMHE method was somewhat less than that of the computationally intensive maximum likelihood variance components method (Amos et al . 2001). We present comparisons of the empirical distributions of the NMHE test to its limiting distributions for a range of numbers of traits. The distribution of the NMHE test appeared to conform satisfactorily to its limiting asymptotic distribution in large samples. Otherwise, empirical critical values for NMHE are somewhat higher than predicted, i.e. the test proposed by Elston et al . (2000) is non-conservative. The use of empirical critical values is therefore recommended for limited sample sizes (less than several hundred families). We also present the results of a linkage analysis performed by the NMHE method on a set of 4 body size-related traits. The method identified meaningful combinations of traits that showed significant linkage on chromosome 2 and suggestive linkage to regions on chromosomes 16 and 17.