The Measurement of Urinary LH, by a Solid-Phase Chemiluminescence Immunoassay

Abstract

SUMMARY.Ovulation in women may be predicted or detected by a simple, solid-phase, chemiluminescence immunoassay for the measurement of urinary LH. An IgG fraction of a donkey antiserum to rabbit immunoglobulins is passively adsorbed to the walls of polystyrene tubes. Human chorionic gonadotrophin-succinyl-butyl-ethyl-isoluminol and a primary antibody (rabbit anti-human LH) is incubated with samples of early morning urine. After the binding reaction, the solution is removed by aspiration. The antibody-bound fraction is washed twice with buffer. Sodium hydroxide is added and the mixture incubated. After cooling, luminescence is initiated by oxidation of the label with microperoxidase/hydrogen peroxide and the signal integrated.The method has been evaluated in terms of sensitivity, within-and betweenbatch precision, bias and parallelism. The time interval between the peak day of LH in EMU and maximum follicular diameter during 38 menstrual cycles was -24 h (11 %), 0 h (50%), + 24 h (28%) and + 48 h (II %).Cyclical ovarian function is associated with characteristic changes in the secretion of ovarian and pituitary hormones;' In particular, ovulation is preceded by an increase in the frequency and amplitude of the pulsatile release of luteinising hormone (LH).2 Consequently, rapid radioimmunoassays (RIAs) have been developed for the measurement of LH in serial samples of peripberalv': 4 or capillary plasma," and defined changes in immunoreactivity used as indices of impending ovulation.Related studies" have shown that there are two components to the half-life of LH in the peripheral circulation (approx. 20 and 180 minutes respectively), and the main metabolites are rapidly excreted in the urine." Consequently, a more practical reference method for the detection of ovulation has involved the measurement of LH by RIA in daily samples of Address for correspondence: Professor W. P. Collins, Department of Obstetrics and Gynaecology, King's College School of Medicine, Denmark Hill, London SES 8RX, UK. 284 early morning urine (EMU).H In addition, the collection of urine (every 2 to 4 hours) under carefully controlled conditions has enabled defined changes in the excretion rate of LH (U/h) to be used for predicting the appropriate time for oocyte recovery prior to extracorporeal fertilisation.T he increasing usefulness and availability of RIA, however, has raised several problemsIII and alternative labels have been proposed which overcome the disadvantages while retaining the specificity of the antigen-antibody reaction. II For example, Edwards et al.~have used a semi-quantitative haemagglutination immunoassay for the immediate prediction of ovulation, which involves the use of microtitre plates and the serial dilution of each urine sample. In this report a description is given of a quantitative chemiluminescence immunoassay (CIA) for the measurement of urinary LH. The method is assessed for sensitivity, precision, bias and parallelism, and the clinical value of using the peak excretion of LH in EMU as a reference point for ...