Time-resolved immunofluorometric assay of sex-hormone binding globulin

Abstract

A time-resolved immunofluorometric assay (trIFMA) for human sex-hormone binding globulin (SHBG) is described in which antibody-coated tubes or microtiter strip-wells and a europium (Eu) chelate-labeled monoclonal antibody are used. The trIFMA sensitivity is similar to that of other SHBG immunoassays, and other analytical variables compare favorably with an SHBG immunoradiometic assay (IRMA) kit and a steroid binding capacity assay: the interassay coefficient of variation (CV) is <8% and the intra-assay CV is <6% for concentrations between 6 and 200 nmol/L. The reference intervals (means ± SD) for SHBG concentrations (nmol/L) in serum from 10 men, 10 women, and 10 pregnant women were 23 ± 12, 65 ± 39, and 439 ± 122, respectively. In 14 hirsute women the mean ± SD serum SHBG concentration (37 ± 21 nmol/L) was significantly lower (P<0.01) than the mean for an age-matched, nonhirsute female comparison group. The trIFMA is technically simple, requires no centrifugation or separation reagent, and takes a counting time of only 1 s. In addition, the Eu-label is nontoxic, presents no waste-disposal problems, and has a long shelf life.