A comparative study between radioreceptor assay and radioimmunoassay for hCG in patients with trophoblastic disease.

The results of a urinary quantitative radioreceptor assay (RRA) were compared with those obtained with an established specific radioimmunoassay (RIA) for hCG in a group of patients with trophoblastic disease. A good correlation (r = 0.95) was found between the two methods for values greater than 10 mIU/ml of hCG. A specific RIA for hCG should be used when the hCG levels fall below 10 mIU/ml. With the use of this urinary RRA, the clinician can follow patients with hydatidiform more for up to 10 weeks after evacuation and have the hCG titer available on the same day the specimen is obtained.