Elimination of Human Chorionic Gonadotropin in Sandwich Enzyme Immunoassay for Human Thyroid-Stimulating Hormone in Serum

A method to eliminate human chorionic gonadotropin (hCG) in the sandwich enzyme immunoassay for human thyroid-stimulating hormone (hTSH) in serum is described. hTSH in serum containing hCG was reacted with dinitrophenyl monoclonal mouse anti-hTSH -subunit IgG1, and the complex formed between the dinitrophenyl IgG1 and hTSH was trapped onto affinity-purified rabbit (anti-dinitrophenyl bovine serum albumin) IgG-coated polystyrene balls. hCG in the test serum was largely eliminated by washing the polystyrene balls. Subsequently, the complex on the polystyrene balls was reacted with affinity-purified rabbit anti-hCG Fab′-peroxidase conjugate followed by washing. The complex of the dinitrophenyl IgG1, hTSH and the conjugate was eluted with dinitrophenyl-L-lysine from the polystyrene balls, to which hCG had been nonspecifically adsorbed, and was trapped onto clean polystyrene balls coated with affinity-purified rabbit (anti-mouse IgG) IgG. Peroxidase activity bound to the (anti-mouse IgG) IgG-coated polystyrene balls in the absence and presence of hTSH was not significantly affected by the presence of up to 75,000 IU of hCG per liter of serum. As a result, serum hTSH could be sensitively measured with little interference by hCG.