IMMUNOMETRIC ASSAYS OF LUTEINIZING-HORMONE (LH) - DIFFERENCES IN RECOGNITION OF PLASMA-LH BY ANTI-INTACT AND BETA-SUBUNIT-SPECIFIC ANTIBODIES IN VARIOUS PHYSIOLOGICAL AND PATHOPHYSIOLOGICAL SITUATIONS

Restricted immunoreactivity of plasma luteinizing hormone (LH) has bee n described in some subjects when assayed with certain methods involvi ng antibodies against intact LH. We have compared the performance of t he Amerlite LH-30 (A) and Delfia LH(Spec) (D) assays (which include an ti-intact and beta-specific antibodies, respectively) in normal and pa thological conditions. As shown previously, results of the two systems were highly correlated with each other and, as we show here, with tho se of a bioassay. We found eight outliers (results outside the 95% con fidence interval of the regression) among 427 samples studied from 121 subjects. Of the outliers, five had Delfia results in a range (<1 IU/ L) that was associated with poor assay precision for that assay, and t he ratios of their values by both methods (A:D ratios) were very low. This ratio was affected by endocrine status, e.g., was lower in postme nopausal women than in premenopausal controls, and varied intraindivid ually within the same menstrual cycle. The restricted immunoreactivity described previously for assays involving anti-intact LH antibodies m ay, in part, reflect these differences, which, in turn, may reflect th e presence of isoforms (e.g., glycoforms) that are differentially reco gnized by assays that have different antibody configurations.