Comparison of double antibody and solid-phase radioimmunoassays

Abstract

Two commonly used radioimmunoassay (RIA) procedures, double antibody assay and solid-phase assay, have been compared using the same reagents and conditions. Mouse hemoglobulin—horse anti-mouse hemoglobulin system was chosen for this study. The antibody was found to have more binding capacity in soluble form than in the Sepharose-bound form. The inhibition curves in both the assay systems were shifted to higher inhibitor concentration at higher control binding levels. At 40% control binding level, the double antibody RIA was found to be 2.7 times more sensitive than the solid-phase RIA. The reason for this most probably lies in the lower binding capacity of the Sepharose-bound antibody which necessitates the use of higher amounts of the antibody to reach 40% control binding.