False diagnosis and needless therapy of presumed malignant disease in women with false-positive human chorionic gonadotropin concentrations

Background 12 women were diagnosed of having postgestational choriocarcinom a on the basis of persistently positive human chorionic gonadotropin (hCG) test results in the absence of pregnancy. Most of the women had extirpative surgery or chemotherapy, or bath, without significant diminution in hCG ti tre. Our aim was to assess whether the hCG concentrations were false-positi ve test results. Methods Samples were tested for hCG, hCG free beta subunit, and hCG beta-co re fragment. Assay kinetics were also assessed, and samples were tested ind ependently by competitive RIA. False-positive hCG concentrations were ident ified by two criteria: detection of hCG in serum and lack of detection of h CG and its degradation products in urine; and wide variations in results fo r different hCG assays. We corroborated false-positive hCG values by the la ck of parallel changes in hCG results when serum was diluted, by false dete ction of other antigens, and by failure to detect hCG with in-house assays. Findings All 12 women met both criteria for false-positive hCG, and all had corroborating findings. In all 12 cases, a false diagnosis had been made, and most of the women had been subjected to needless surgery or chemotherap y. Assay kinetics indicated that heterophilic antibodies were responsible f or the false-positive results. As a result of our findings all further ther apy was stopped. Interpretation Current protocols for the diagnosis and treatment of chorioc arcinoma should be modified to include a compulsory test for hCG in urine.