A chemiluminescent immunoassay (LIA) for testosterone

An immunoassay method for testosterone was developed in which the binding reaction is monitored by a chemiluminescent tracer (testosterone-3-carboxymethyloxime-aminobutyl-ethyl isoluminol; T-3cmo-ABEI). When undergoing oxidation at high pH values by a microperoxidase-hydrogen peroxide system, the chemiluminescent tracer emits light with a relative high quantum efficiency (detection limit = 0.5 fmol). A heterogeneous immunoassay, using dextran-coated charcoal for separation of bound and free forms of the ligand, was developed and assessed, always when performing parallel studies in RIA. Computer analysis of the results demonstrated that the performance of the chemiluminescent immunoassay (LIA) was entirely comparable to that of RIA in terms of sensitivity, precision, specificity and accuracy. Plasma samples of normal subjects and of patients affected by disorders of androgen secretion were assessed by both the procedures (RIA and LIA) and the results obtained using the two methods were superimposable (n=33; r=0.97). Aliquots of the incubation medium of a bioassay for serum hLH measurements (RICT) were also measured by the LIA procedure and by RIA - the results were similar. The proposed LIA method for testosterone, which does not require radioactive material, appears fully suitable for clinical purposes. (author)