The use of a radioreceptorassay of human chorionic gonadotropin for the diagnosis and management of ectopic pregnancy.

The radioreceptorassay of human chorionic gonadotropin (hCG), with a sensitivity of 50 pg or 3 mIU/ml of plasma, has provided almost 100% reliability in detecting pregnancy after the first missed cycle. This test may be performed within 1 hour and is ideally suited to the clinical detection of ectopic pregnancy, especially in patients who require immediate surgical intervention. Thirteen patients with suspected ectopic pregnancy were evaluated by the radioreceptorassay, one of whom was followed with four separate determinations. The results of the assay were subsequently compared with those of hemagglutination pregnancy tests, clinical symptoms, and pathologic findings. All of the patients were diagnosed accurately by the radioreceptorassay, even when hemagglutination tests yielded a false indication of pregnancy. By this assay, the hCG levels during ectopic pregnancies are generally lower than those found during a normal intrauterine pregnancy; in addition, pregnancy may be detected much earlier (prior to the rupture) than is possible by hemagglutination tests. Furthermore, the diagnosis of ectopic pregnancy may be excluded for patients admitted to the hospital with acute abdominal emergencies.