A highly sensitive and specific sandwich enzyme immunoassay for detection of human chorionic gonadotropin in trophoblastic disease.

A highly sensitive and specific two-site enzyme immunoassay (EIA) kit for human chorionic gonadotropin (hCG) has been examined and applied to the detection of hormones in the serum of normal individuals and patients with trophoblastic disease. This EIA uses a solid phase coupled antibody to the unique COOH terminal peptide region of the hCG beta-subunit (beta-CTP) and an enzyme conjugated monoclonal antibody to the hCG beta-subunit. The overnight 2 step assay measured as little as 0.2 mIU/ml serum without hLH interference and a rapid one step assay was newly developed in our laboratory. Assays of serum from normal men and nonpregnant women of reproductive age indicated that most individuals did not have detectable serum levels of hCG immunoreactivity, although a minority had minute amounts. In contrast, women with non-functional ovaries had detectable levels of hCG immunoreactivity with a mean value of 0.86 mIU/ml serum. The extremely high sensitivity and specificity of the EIA in detecting hCG provides substantial advantages for the detection of early pregnancy and for monitoring trophoblastic tumors.