Human Chorionic Gonadotropin Assays and Their Uses

Frequent false positive beta human chorionic gonadotropin tests in immunoglobulin A deficiency

A patient with IgA deficiency had a series of positive serum pregnancy tests which led to medical and surgical procedures for suspected molar pregnancy. These tests were found to be falsely positive due to heterophile antibody. The aim of this study was to determine the frequency of false positive betahCG assays in sera of IgA deficient patients. Sera from a panel of IgA deficient (IgA < 7 mg/dl) patients were tested for the presence of betaHCG using three different assays, and also for IgG anti-goat and anti-mouse antibodies. Patients were seen at Mount Sinai Medical Center and included 54 patients (ages 1-80 years, 32 females, 22 males) with IgA deficiency. Thirty percent of 54 IgA deficient patient sera yielded positive pregnancy tests by one or more of the three betahCG assays, however, none of the patients were pregnant. In comparison to sera of normal controls, 39% of the patient sera contained significant amounts of anti-goat antibody and 18% contained significant amounts of anti-mouse antibody. While heterophile antibodies are common in IgA deficient serum, false positive assays for betahCG in IgA deficient serum have not been previously reported. The possibility of false positive test results should be considered prior to invasive procedures in IgA deficient patients.

Gynecologic tumor markers

The advent of monoclonal technology has increased the potential utility of antibody-dependent tumor marker assays in gynecologic oncology. The availability of unlimited quantities of several pure monoclonal antibodies directed against novel epitopes on tumor-associated antigens has permitted development of highly sensitive assays for serum markers. Traditional assays for human chorionic gonadotropin (hCG), NB/70K and TA-4 have been improved. CA 125 has provided a useful first-generation marker for monitoring ovarian cancer and triaging patients with pelvic masses, despite limitations in sensitivity and specificity. In the next decade, the challenge is to identify new markers that will complement CA 125 in monitoring ovarian cancer and facilitate screening for occult early-stage disease. Strategies involving multiple markers and modalities may be required. Some markers may emerge through a more fundamental knowledge of the biology of gynecologic neoplasms, including the expression of growth factors and their receptors. Finally, the application of monoclonal antibodies to immunohistochemistry and radionuclide imaging also may provide new areas of diagnostic application for monoclonal antibodies in gynecologic oncology.