[Studies of enzyme-linked immunoassay for testosterone using penicillinase as label]

An enzyme-linked immunoassay (EIA) for testosterone was developed based on penicillinase as the marker enzyme. The assay proposed requires a conjugate containing penicillinase as the enzymatic component, penicillin Vas substrate and an iodine-starch reagent as the chromogenic component. The binding of conjugate molecules results in the transition of the iodic complex from dark blue to colourless. delta A (the difference between the blank and the testosterone) vs log C was linear over the range 10(-7) - 10(-2)mg/ml (r = 0.9969), with a limit of detection 25 pg per disc. The CVs of day to day and within day for plasma testosterone were < 3.3% and 5.9%, respectively. There was a good correlation between the values obtained by EIA and radioimmunoassay (r = 0.937).