Enzymeimmunoassay of unconjugated estriol in serum and saliva during pregnancy.

An enzymeimmunoassay (EIA) for unconjugated estriol was developed. Estriol-6-CMO-BSA was used as antigen for the antiserum production with low cross reactivities to estrone (0.3%) and estradiol (0.17%). The enzyme conjugate (estriol-peroxidase) was prepared using the mixed anhydride reaction. The antibody bound estriol fraction was separated from the free fraction with the double antibody technique. The test requires a simple photometer for the measurement of enzyme label. The developed estriol-EIA needs a short incubation time (2 hrs). The normal values of estriol in serum were determined. The results are in good agreement with the results of RIA. Furthermore, we found an inverse diurnal rhythm of serum and salivary estriol in comparison to the cortisol level. Low estriol levels in the morning and high estriol concentration in the evening are indices of fetal health. Decreased estriol levels in the morning of several days were found in pathological pregnancies (intrauterine fetal death, fetal distress, hepatose).