Solid-phase competitive and sandwich-type erythro-immunoassays for human chorionic gonadotropin

Abstract

A simple '1-step' competitive erythro-immunoassay for human chorionic gonadotropin (hCG) employing V-shaped well microtitration plates coated with monoclonal anti-β-hCG antibody has been described. hCG of the test sample competes with the antigen-coupled sheep erythrocytes for binding to the antibody on the solid surface. The assay is able to detect up to 31.25 ng hCG/ml. A higher sensitivity enabling detection up to 0.25 ng hCG/ml is attained by the sandwich erythro-immunoassay using a chimera antibody prepared by coupling monoclonal anti-α-hCG antibody to an affinity-purified polyclonal antibody specific for sheep erythrocytes. This assay is amenable to the qualitative as well as quantitative use as described. The urinary components do not interfere in the assay. Results obtained by this assay on 47 human urine samples correlated well with the values obtained by '2-step' sandwich enzyme immunoassay and radioimmunoassay.