[A rapid and direct 125 I-based radioimmunoassay for unconjugated estriol in pregnancy serum and its clinical application (author's transl)].

A rapid and simple R.I.A. method for serum unconjugated estriol in pregnancy had been studied for its usefulness as a routine obstetrical test to assess fetal well-being. Diluted serum samples or known amounts of standard estriol were applied with 125 I-estriol on pre-packed minicolumns of Sephadex G-25, followed by appropriately diluted antiserum. During incubation, the columns were counted in an Auto Well gamma-System to read the total counts (T). After a 90 minute incubation period, the columns were eluted with a buffer solution to remove the bound fraction, and the free estriol remaining in the columns was counted (F). Two quality control samples and sera from 74 pregnant women were analysed by this new method, and the results were compared to those obtained by the conventional radioimmunoassay method. The new column method is simple, specific and accurate. Results can be calculated within 4 hours after 30 sample sera are brought into the laboratory. Within and between assay coefficients, variations are 12.6 and 13.5%, respectively. This method correlates well with the results of the conventional method (r=0.7088, p less than 0.001), which requires almost 2 full days to process the same numbers of samples. Results of clinical cases as well as advantages of measuring free-circulating estriol in pregnancy are discussed.