CA125 antigen levels in obstetric and gynecologic patients.

An immunoradiometric assay using a monoclonal antibody detects an antigenic determinant (CA125) that is present in more than 80% of epithelial ovarian cancers. CA125 levels are elevated in the sera of 16% of women in the first trimester of pregnancy and is found in very high concentration in amniotic fluid. In 988 nonpregnant patients with benign gynecologic disorders, CA125 was greater than 65 U/mL in 1% on a single determination and in 0.5% with two determinations. Given the low rate of positivity in benign gynecologic disease, the CA125 assay may deserve further evaluation for the early detection of ovarian carcinoma.