Experimental determination of the operative parameters for a double antibody solid phase radioimmunoassay of luteinizing and follicle-stimulating hormones in serum.

The experimental parameters of a Double Antibody Solid Phase (DASP) radioimmunoassay (RIA) for the determination of serum luteinizing (LH) and follicle-stimulating (FSH) hormones, are described. The lowest detection limits can be fixed at about 20 pg LH and about 10 pg FSH. Evidence of parrallelism among the dose-response curves and the dilution curves of different sera is provided for FSH-RIA and for about 92% of the tested sera for LH-RIA. The antisera dilution curves are reported (final titres: (/160 - 10(3) for anti-LH and 1/40 - 10(3) for anti-FSH). The traditional cross-reaction study in buffer indicates that 5.38 and 46.8) muU TSH/ml mimic 1 ng LH/ml and 1 ng FSH/ml respectively. The regression-line equations of antigen recovery (f = found, e = expected) are: lH f = 0.94 LH e + 0.91 and FSH f = 1.05 FSH e + 0.17; the same equations when TSH is added become: LH f = 1.30 LH e + 1.46 and FSH f = 1.40 FSH e -- 0.37. It is concluded that LH-RIA is interfered by TSH over 8-10 muM TSH/ml and in function of TSH concentration; FSH-RIA is not interfered by TSH up to 4-5 ng FSH/ml; for higher FSH levels, TSH interferes according to a linear law (angular coefficient 1.40) and not in function of its concentration. LH and FSH levels throughout normal menstrual cycle in follicular phase, centre peak and luteal phase are: 3.14 +/- 1.16, 16.71 +/- 12.99, 2.31 +/- 1.04 ng LH/ml (mean +/- 2SD) and 3.57 +/- 0.95, 5.72 +/- 2.90, 2.57 +/- 0.80 ng FSH/ml (mean +/- 2SD) respectively. Finally, the within-assay coefficient of variation is 7.65% for LH-RIA and 3.16% for FSH-RIA.