SYNTHESIS OF A NOVEL BIOTIN-ESTRADIOL CONJUGATE AND ITS USE FOR THE DEVELOPMENT OF A DIRECT, BROAD RANGE ENZYME-IMMUNOASSAY FOR PLASMA ESTRADIOL

The synthesis and purification by high pressure liquid chromatography of a novel biotinoyl-diaminodioxaoctaneestradiol conjugate is describe d. The conjugate was used for the development of an enzyme immunoassay (EIA) for the direct determination of estradiol in human plasma. This assay was characterized by a low limit of detection (77 pM) and a bro ad working range. Estradiol concentrations ranging from 77 to 24300 pM , i.e. from the lower levels observed in the follicular phase of the n ormal menstrual cycle to the very high levels attained during hypersti mulation for in vitro fertilization, could be determined directly in u ndiluted plasma samples. Intra-assay variation ranged from 3.6 to 10.9 % and interassay variation from 6.1 to 12%. The results obtained by th e present EIA correlate well with target values obtained by isotope-di lution gas chromatography-mass spectrometry (r = 0.96) and with result s obtained by a direct RIA (r = 0.97). The EIA requires no special app aratus, is simple, fast and robust, and could be applied in any clinic al laboratory.