Diagnostic value of a rapid HCG-beta-subunit radioimmunoassay in cases of suspected ectopic pregnancies.

A rapid and sensitive RIA specific for the beta-subunit of HCG was developed. This RIA gives the results in less than 3 hours, and is able to detect the pregnancy 12 days after the midcycle LH-peak. The clinical reliability was evaluated by assaying plasma samples from 128 patients with acute gynecologic symptoms and suspicion of ectopic pregnancy. Other diagnostic methods including urinary pregnancy test (117 patients), culdocentesis (57 patients), and endometrial curettage (66 patients) were also performed. The final clinical diagnosis was ectopic pregnancy in 45 cases, intrauterine pregnancy in 31 cases, and no pregnancy in 52 cases. The rapid HGC-RIA gave a positive result in 93%, 97%, and 6% of these patient groups, respectively. The conventional diagnostic methods were less reliable and gave a positive result in only 52-59% of the ectopic pregnancies. Three false negative results (7%) in the HCG-RIA were obtained in cases of ectopic pregnancy. Three false positive results (6%) were obtained in patients not pregnant. The results show the superiority of the HCG beta-subunit RIA compared to the conventional diagnostic methods in the diagnosis of ectopic pregnancy.