Testicular cancer secretes intact human choriogonadotropin (hCG) and its free β-subunit: Evidence that hCG (+hCG-β) assays are the most reliable in diagnosis and follow-up

Abstract

Human choriogonadotropin (hCG) and free hCG-β values for 934 serum samples from patients with seminomatous or nonseminomatous testicular cancer were measured by highly specific immunoradiometric assays (IRMAS). In non-seminoma samples, hCG and hCG-β were highly correlated (r = 0.82, P <0.001). Of 112 "marker-positive" seminoma samples, only 46 (41.1%) showed both increased hCG and hCG-β. In 39 cases (34.8%) only hCG-β and in 27 cases (24.1%) only dimer-hCG was increased. This makes the determination of hCG and hCG-β, either by two assays or by a single hCG (+hCG-β) assay, most reliable in these patients. For all samples, hCG (+hCG-β) was measured by a polyclonal RIA and a monoclonal IRMA, which differed in their cross-reactivities with hCG-β (234% and 720%, respectively). The hCG (+hCG-β) IRMA, as a result of its higher hCG-β cross-reactivity, was superior to the hCG (+hCG-β) RIA in detecting slightly increased hCG-β. Additionally, 11 widely used commercial hCG kits were tested for their hCG-β cross-reactivities and showed values between <3% and 264%.