Studies on Immunological Assay of Urinary Estrogens. III. A New Latex Agglutination Inhibition Reaction Method

A new, simple and rapid method for the immunological determination of estrogens in pregnancy urine is described. The principle of this method is based on the latex agglutination inhibition reaction in a solid-solid system. An antibody latex reagent (Ab-Latex) was obtained by sensitizing latex particles with anti-estriol 16-glucuronide antibody which had been raised in a goat. Estriol 16-glucuronide-bound latex reagent (E3-16-G-Latex) was prepared by the condensation of polyacrylic acid combined with estriol 16-glucuronide (E3-16-G) and lysine-latex which had been prepared from carboxylate modified latex. Hexamethylenediamine was used for the binding of E3-16-G to polyacrylic acid. The latex agglutination inhibition tests were performed on opaque glass slides. One drop (30μl) of Ab-Latex suspension followed by one drop of E3-16-G-Latex suspension was added to one drop of diluted urine sample and mixed thoroughly. The slides were rotated gently for 2 minutes, and a macroscopically visible agglutination inhibition pattern was observed in the presence of an estrogen concentration of 0.1μg/ml (as estriol) or more. The estrogen values in urine can be obtained by multiplying the sensitivity by the highest dilution factor able to give a positive reaction. This test cross-reacted not only with free estriol but also with all free and conjugated estrogens having a free hydroxy group at position 3 in the steroid ring. The urinary estrogen values obtained by this method showed a good correlation with those measured by a radioimmunoassay method (correlation coefficient ; 0.9845, regression line ; y=0.823x-0.614). When this method was compared with a semi-quantitative determination method, the hemagglutination inhibition reaction (E3 HAIR kit), the results of the two methods were in fairly good agreement.