Enzyme-linked immunosorbent assay of CA-125 in serum of patients with endometriosis: efficacy in diagnosis.

We used an enzyme-linked immunosorbent assay to quantify CA-125, a cancer antigen, in serum of patients with endometriosis. Concentrations of CA-125 in 103 patients with untreated endometriosis significantly (P less than 0.005) exceeded those for 31 controls with no evidence of disease: 9.1 (SD 12.3) vs 2.2 (SD 3.2) arb. units/mL. Values for patients with treated endometriosis were lower (2.3, SD 2.6, arb. units/mL, n = 9) than those for patients with untreated endometriosis. The mean concentrations of CA-125 in different stages of untreated endometriosis were 4.8 (SD 4.5), 7.1 (SD 9.9), 9.8 (SD 13.2), and 10.8 (SD 13.0) arb. units/mL for Stages I, II, III, and IV, respectively. The differences between controls and each stage were statistically significant (for all stages: P less than 0.05). We also assayed serum sampled from controls and patients with untreated endometriosis during menstruation (Group A) and during nonmenstruation (Group B). The efficacy of the present assay for concentrations of CA-125 in serum of patients with endometriosis was greater for Group B than for Group A. Evidently, determination of CA-125 in serum by the present assay may assist in such diagnosis.