A sensitive solid phase enzymeimmunoassay for testosterone in plasma and saliva

Abstract

A sensitive, solid phase enzymeimmunoassay suitable for determining testosterone concentrations in small aliquots of plasma (20μ1) and saliva (200μ1) has been developed. A solid phase antiserum raised against a testosterone-11α-hemisuccinate/bovine serum albumin conjugate was prepared by coupling to cyanogen bromide activated cellulose. The “enzyme label” was a covalently linked testosterone/horseradish peroxidase conjugate. The assay had a lower limit of sensitivity of 4pg/assay tube and satisfied accepted criteria of specificity and precision. Testosterone concentrations determined by enzyme-immunoassay were in excellent agreement not only with a gas liquid chromatography/mass spectrometry procedure (r = 0.96, n = 12) but also with the radioimmunoassay in routine use (r = O.95, n = 12). The EIA can therefore replace RIA in both the small clinical laboratory and high throughput service centres for determining plasma and salivary testosterone concentrations. In normal males salivary testosterone concentrations reflected circulating steroid levels and indicated the possibility of assaying saliva rather than plasma in clinical studies.