Phantom hCG and phantom choriocarcinoma

Phantom hCG and phantom choriocarcinoma syndrome (pseudo-hypergonadotropine mia) refers to persistent mild elevations of hCG, leading physicians to tre at patients with cytotoxic chemotherapy for choriocarcinoma when in reality no true hCG or trophoblast disease is present. We report here three cases of the phantom hCG and phantom choriocarcinoma syndrome referred to the hCG Reference Service. In the first case, low levels of hCG were detected in s erum (49 to 89 IU/liter) 11 months after the patient had a miscarriage. The presumptive diagnosis of choriocarcinoma was made. After two courses of ch emotherapy and a hysterectomy low levels of hCG were still detected. Sample s were sent to the hCG Reference Service. While low levels of hCG were dete cted in serum by three different assays (17, 22, and 9.2 IU/ml), no hCG was detected in the urine. When serum was diluted, levels did not decrease par allel to the dilution. The lack of dilutional parallelism and absence of ur ine reactivity indicated that the molecule measured was a pseudogonadotropi n or phantom hCG, an interfering substance in hCG tests. Therapy was halted . In the second case, a positive serum pregnancy test was recorded 7 years after a normal pregnancy. A pelvic ultrasound and a laparoscopy revealed no pregnancy. Blood hCG levels stayed between 48 and 74 IU/liter over a 3-mon th period. Samples were sent to the hCG Reference Service. Low levels of hC G, free beta-subunit, and beta-core fragment were detected in serum using f our specific assays. No hCG immunoreactivity was found in the urine sample. None of the four assay results declined parallel to dilution. Again, phant om hCG was diagnosed. In the third case, a positive serum pregnancy test wa s recorded 1 year after the patient had a normal pregnancy. A pelvic ultras ound revealed no fetal sac. Low levels of hCG (51-135 IU/liter) persisted f or 3 months. A preumptive diagnosis of choriocarcinoma was again made. Afte r three cycles of chemotherapy, low levels of hCG were still detected. Samp les were sent to the hCG Reference Service. Low levels of hCG immunoreactiv ity were detected in serum in just one of three hCG assays (13 IU/liter). N o immunoreactivity was detected in the urine sample. Again, phantom hCG was diagnosed, and all therapy was halted. Care is needed in interpreting pers istent low levels of hCG in patients with no history of trophoblast disease . It is important for the laboratory to show dilutional parallelism in the hCG results and presence of hCG in serum and urine samples in order to excl ude phantom hCG before diagnosing choriocarcinoma. (C) 1998 Academic Press.