Diagnosis of pregnancy with a radioreceptor assay for hCG.

A new serum assay for human chorionic gonadotropin, the radioreceptor assay (RRA), was compared with three commercial urinary agglutination inhibition pregnancy tests (AITs) in a group of women with suspected early pregnancies and ectopic gestations. The accepted definitions by which a laboratory test is characterized, including clinical sensitivity and specificity as well as predictive value of positive and negative tests and efficiency, were calculated for each test in three different time periods of gestation: less than 7 days, between 7 and 14 days, or more than 14 days after the expected menses had been missed. The results of the study showed that the RRA had greater clinical sensitivity and efficiency than the AITs in cases of both early gestation and ectopic pregnancy. The RRA has the disadvantages of requiring the capability to handle radioactive materials and gamma counter. This test is chiefly useful for those patients desiring early termination of pregnancy and those infertility patients anxious for early confirmation of pregnancy.