Diagnosis and management of pregnancy by the radioreceptorassay of human chorionic gonadotropin

Abstract The radioreceptorassay (RRA) of human chorionic gonadotropin (hCG) has provided to the clinician one of the most sensitive, rapid, and reliable tests for the diagnosis and management of pregnancy. Since the “receptor” recognizes only the native form of the hormone, the RRA combines the specificity of the bioassay and the sensitivity of the radioimmunoassay. The accuracy of the RRA has been demonstrated in more than 10,000 pregnancy tests performed in our laboratory. The “yes and no” pregnancy kit based on the RRA of hCG (Biocept-G, Wampole Labs., Cranbury, New Jersey) provides a sensitivity of 200 ml.U. of hCG per milliliter, which is approximately sixfold greater and considerably more reliable than the available hemo- and latex-agglutination tests in the detection of early pregnancy. The quantitative RRA of hCG with a sensitivity of 6 ml.U. per milliliter can detect normal pregnancy one week after documented ovulation and is nearly 100 per cent accurate around the time of the first missed menstrual period. Serum hCG levels that are twofold greater than those encountered in normal pregnancy at four to eight weeks' gestation indicate twin pregnancy, which has been confirmed at eight to ten weeks by sonography. The quantitative RRA of hCG can also determine the quality of the pregnancy as well as predict ectopic pregnancies, threatened abortions, spontaneous abortions, and occult pregnancies. Thus, the RRA of hCG has become an invaluable aid to the clinician in providing better obstetric care with reduced morbidity in abnormal pregnancies. Similarly, early and reliable confirmation of pregnancy has permitted the performance of miniabortion before seven weeks of pregnancy and has eliminated such procedures in the absence of pregnancy. Likewise, the RRA of hCG has provided a rapid, highly sensitive, and useful marker in the detection of trophoblastic disease and ectopic tumors.