Comparison Between Four Radioimmunoassays for Plasma Estriol

Abstract

We have compared the results obtained for plasma estriol (E₃) when four radioimmunoassay methods were used to measure this steroid during various stages of human pregnancy. The first method used a nonspecific antiserum combined with a chromatographic step. The second method utilizes as binding reagent a specific antibody against estriol combined with the same chromatographic step. The last two methods involve solvent extraction only, combined with the specific antiserum. Dichloromethane and ether respectively are used as solvent. The lowest levels of E₃ were obtained with methods I and II. With dichloromethane extraction the E₃ levels were comparable to those obtained with methods I and II. When using ether extraction the E₃ levels were in most cases two to four times higher. Even with highly specific anti- E₃ sera, chromatography is still required to achieve specificity.