Discordant inter-kit results in the radioimmunoassay for choriogonadotropin in serum.

Discordant results for concentrations of choriogonadotropin (HCG) in sera from five of 162 women are reported, as determined with four commercial radioassay kits: Becton-Dickinson, Clinetics, Corning, and Hybritech. Results ranged from 11.2 to 36.7 int. units/L, when assayed with the Becton-Dickinson kit, but HCG was not detectable when assayed with the other kits. None of the patients was pregnant, and none had evidence of persistent trophoblastic or nontrophoblastic disease. Concentrations of lutropin, follitropin, thyrotropin, triglycerides, cholesterol, protein, and albumin were normal. Assay of diluted sera did not parallel the standard curve, and nonspecific binding in the patients' samples was negligible. Some kits for HCG may be influenced by inherent methodological factors or interfering serum constituents, which can lead to spurious results.