Direct radioimmunoassay of testosterone in human saliva

A simple direct radioimmunoassay for testosterone in 400 μl of whole human saliva is reported. Neither extraction nor chromatography is needed. The direct assay involves a commercially available, highly selective antiserum raised against testosterone-19-(O-carboxymethyl)-ether-BSA, an iodinated tracer, a serum added to give parallel inhibition of analyte and tracer binding to serum proteins and a double antibody/polyethylene glycol separation technique. The lower limit of determination is about 3 pM salivary testosterone and the calibration curve covers the range of clinical interest both for males and females (0–868 pM). The assay is specific as judged from recovery and dilution tests, from the cross-reactivity of the antiserum used and from comparisons with an extraction procedure. Within-assay and between-assay relative standard deviations are 4.1, 1.9, 10.5% and 6.3, 2.8, 15.3% for saliva samples with testosterone concentrations of 310, 117 and 52.7 pM, respectively.