Pregnancy testing. 2. Radioreceptor assay.

Of the various sensitive assays for human chorionic gonadotropin, the radioreceptor assay is now the most practical and should be used for the early diagnosis of pregnancy (35 days or less after the last normal menstrual period). Serial measurement of this hormone by the beta subunit radioimmunoassay provides a valuable guide to the management of trophoblastic disease.