Monoclonal versus polyclonal antibody radioimmunoassay against the beta-subunit of human chorionic gonadotropin in patients with gestational trophoblastic neoplasia.

The level of human chorionic gonadotropin (hCG) in series of sera from eight patients with gestational trophoblastic neoplasia was measured by monoclonal antibody and polyclonal antibody radioimmunoassay. A comparative analysis was performed. Three commercially available monoclonal anti-beta-subunit of hCG (beta-hCG) antibodies were evaluated and the most specific and sensitive one was chosen to develop a quantitative beta-hCG radioimmunoassay. beta-hCG radioimmunoassay kits from Nuclear Medical Systems, Inc., and Clinical Assays served as polyclonal antibody assays. Results obtained with the monoclonal antibody radioimmunoassays demonstrated a high degree of correlation (r greater than 0.95, p less than 0.01) with those obtained by the polyclonal antibody techniques; however, the sera from one patient continuously demonstrated a low level of hCG in the monoclonal antibody radioimmunoassay while registering undetectable levels in the polyclonal antibody assays. Although the monoclonal antibody radioimmunoassay appears to be specific and fairly sensitive, the results indicate that, with current technology, there is no special advantage to employing this assay to measure hCG in patients with gestational trophoblastic neoplasia.