Radioimmunoassay of Estriol-16-Glucuronide

A specific radioimmunoassay of estriol-16-glucuronide has been developed, using an antiserum obtained by immunization of rabbits against estriol-16-glucuronide-BSA. The assay does not require hydrolysis, extraction and purification, but only a dilution of the crude sample. This constitutes the main advantage of the precedure. Accuracy, precision and sensitivity of the method are similar to those reported for other radioimmunoassays of estriol. Its specificity is good for the measurement of estriol-16-glucuronide in urine and in amniotic fluid, but not in serum of pregnant women, which apparently contains material interfering with the radioimmunoassay, at dilutions of less than 1/100. A significant correlation was observed between estriol-16-glucuronide and total estriol in urine during pregnancy; however, the contribution of the glucuronide to the total increases as pregnancy progresses, rising from 50% for a total of 5 mg/24 h to 85% for a total of 50 mg/24 h. The present radioimmunoassay can be used as a quick and reliable method for the measurement of urinary estriol-16-glucuronide in high risk pregnancies.