A Comparison of the Cyclic Variation in Serum Levels of CA125 Across the Menstrual Cycle Using Two Commercial Assays

Background: Clinicians use CA125, a tumor-associated antigen, primarily to monitor epithelial ovarian cancer. However, CA125 lacks the sensitivity and specificity necessary for population-based screening in healthy women. The purpose of this study was to determine if serum concentrations of CA125 differed across the three phases of the menstrual cycle in healthy, premenopausal women using two commercially available assays. Methods: Healthy, Caucasian women between the ages of 18 and 39 were enrolled using strict criteria to exclude factors known to contribute to CA125 fluctuations. Menstrual cycle regularity was determined using calendars maintained by participants for 3 months. After cycle regularity was established, blood was drawn at three time points for CA125 determination using two commercial assays (i.e., Siemens and Panomics). Results: Regardless of the assay used, CA125 values were highest during menses. The CA125 values decreased 0.2 U/ml per day from menses to the end of the same cycle, which resulted in a net decrease of 5.8 U/ml across the cycle. Conclusions: The two commercial assays for CA125 determination demonstrated good concordance in terms of reference ranges regardless of epitope differences. While CA125 levels changed over the course of the menstrual cycle, these changes may not be clinically significant in healthy women. This study is the first to control for factors known to contribute to CA125 elevations; to quantify a decrease in CA125 levels across the menstrual cycle; and to confirm concordance in the relative decreases in serum CA125 levels across the menstrual cycle between two frequently used commercial assays.