Enzyme immunoassay for human chorionic gonadotropin and its clinical application.

The assay for hCG is important in gynecological and obstetrical fields and has been performed by RIA and radioreceptor assay (RRA). But these procedures use radioisotope which limits popular use. Recently enzyme immunoassay (EIA) has been developed in which procedure the enzyme has been used for labelling in place of radioisotope. The labelling enzyme is stable and has no adverse effect on human beings and its activity is easily measured. In this study, EIA for hCG has been developed. beta-D-Galactosidase (beta-Gal) is preferred because an infinitesimal amount of beta-Gal is easily measured, and MCAE of conjugating agent is used to prevent self-coupling. As solid phase sheep red blood cells were used at first, but now silicone rods are being used because of easy handling. To remove serum interference, sequential competitive method is carried out and 0.5 mIU/ml to 200 mIU/ml of hCG is measurable in 12 h. Coefficients of variation are satisfied. This newly developed assay has been used clinically in diagnosis of brain metastasis of trophoblastic disease, early diagnosis of pregnancy and prognosis of threatened abortion and is now being tried for follow-up of trophoblastic disease.