A number of conditions may cause elevated levels of cancer antigen 125, including endometriosis, pregnancy, uterine fibroids, menstruation, pelvic inflammatory disease, diverticulosis and liver cirrhosis, according to Mayo Clinic. For this reason, CA-125 testing is not a reliable indicator of ovarian cancer for women with normal risk.
The CA-125 test may be given by a doctor to assess the risk for ovarian cancer; however, it only returns a true positive result for approximately 50 percent of stage 1 ovarian cancer patients, and is not a reliable tool for early detection, according to Johns Hopkins. The test has an 80 percent likelihood of returning true positive results for stage 2, 3 and 4 cancer patients, while the other 20 percent of the cancer patients do not have elevated CA-125 levels. Since so many other conditions may cause elevated levels of cancer antigen 125 and result in a false-positive, CA-125 should be used in conjunction with other diagnostic tests in order to determine if ovarian cancer is present.
Other tests such as a transvaginal sonography or rectovaginal pelvic examination can be used in conjunction with a CA-125 test in order to provide more accurate results and lower the incidence of false-positives, states Johns Hopkins.