Semiquantitative assay of human chorionic gonadotropin by a simple and fast immunofiltration technique

An immunofiltration technique for the semiquantitative assay of human chorionic gonadotropin (hCG) was applied in two versions, using different antibodies. One anti-beta hCG subunit was immobilized on a glass microfibre disc in the form of six radially located bars, and the dry disc was placed on a water-absorbing material in a plastic device. A second antibody labelled with horse radish peroxidase conjugate was used in solution. For the colour reaction a solution with tetramethylbenzidine and hydrogen peroxide was used. The number of blue bars appearing on the test disc depended on concentration range of human chorionic gonadotropin. The technique with the monoclonal antibodies, anti-beta hCG and anti-alpha hCG-horse radish peroxidase conjugate, was specific for intact human chorionic gonadotropin, while the technique with the rabbit antibodies, raised against synthetic fragment 122-145-beta hCG and beta hCG-horse radish peroxidase, was useful for both intact human chorionic gonadotropin and its beta-chain. Cross reactions with human lutropin and thyrotropin were negligible. Haemoglobin, urea and various tested drugs did not affect the assay. In the assay of human chorionic gonadotropin in the urine of pregnant women and in sera of patients with trophoblastic diseases, the results from the immunofiltration technique were in accordance with data obtained by classical ELISA and by two commercial kits.