CA125 Measured During Menstruation Can Be Misleading.

Crosby DA1,2, Glover LE1, Martyn F1,2, Wingfield M1,2

1Merrion Fertility Clinic, 60 Mount Street, Dublin 2
2National Maternity Hospital, Holles Street, Dublin 2


The aim of these case reports and literature review is to report the importance of cyclical variation of serum CA-125 levels in two patients with endometriosis. Two case reports and a literature review of cyclical variation in serum CA-125 levels are discussed. There was significant variation in serum CA-125 levels taken during menses and mid-cycle in these two cases. Serum CA-125 levels increase dramatically during menstruation in women with endometriosis. This is important when assessing disease status.

Endometriosis is defined as the presence of endometrial glands and stroma outside the uterus, and is characterized by pain and subfertility1. At present, laparoscopy is considered the gold standard diagnostic test, preferably with histological confirmation2. Symptoms and fertility status should guide patient management rather than biomarker testing. However, serum CA-125 has been used as a biomarker for the disease and serial levels can reflect disease progression or response to treatment3. CA-125 is a well-established glycoprotein biomarker for epithelial cell ovarian cancer and is derived from coelomic epithelia which includes the endometrium, fallopian tube, ovary and peritoneum4. Increased serum CA-125 levels are found with endometriosis3, particularly deep infiltrating endometriosis5 and endometriomata6. A recent systematic review of the diagnostic accuracy of CA-125 in endometriosis found a pooled specificity of 93% and sensitivity of 52%1. Cyclical variation in serum CA-125 levels has been reported, with highest levels detected during menses in women with and without endometriosis7. Even after laparoscopic diagnosis and treatment, levels continue to be elevated during menses8. We report two cases of women with endometriosis, who underwent serial serum CA-125 measurements within the same menstrual cycle: one test was performed during menses on day three and a second was performed mid-cycle.

Case reports
Case 1
A 40-year-old woman with primary subfertility was attending for regular surveillance because of endosalpingiosis diagnosed at laparoscopy two years earlier. She also had endometriosis. As endosalpingiosis has been associated with ovarian cancer9, she was being monitored with three to six monthly CA-125 testing. Over the two years, levels varied between 58 and 67 units/ml. The index test showed a level of 163 units/ml which was of concern due to the elevation. It was noticed, however, that this had been taken during menstruation. A repeat test on day 17 of her cycle gave a result of 69 units/ml.

Case 2
A 36-year-old was referred from her GP with secondary subfertility, severe dysmenorrhoea, and a raised CA-125 level of 554 units/ml. The next available date for surgery was three months hence and there was concern that emergency surgery was indicated because of the CA-125 level. The initial test had been taken during menses. When repeated on day 12 of her menstrual cycle, her CA-125 level was 262 units/ml. She underwent laparoscopy six weeks after her second test, and was diagnosed with stage four endometriosis with an endometrioma.

Our findings demonstrate the significant variation in serum CA-125 levels taken during menstruation and at other times during a woman’s menstrual cycle. These findings have implications for serum CA-125 testing during menses in women with suspected endometriosis, as testing during this time may result in falsely elevated results. Pittaway et al. reported that CA-125 antigen levels increased in women with and without endometriosis during menses7. A case report of presumed endometriosis described a ten-fold increase in CA-125 levels during menses compared to the rest of the cycle (1113+-185.8 units/ml vs. 108+-60.0 units/ml; p<0.001)10.

Kafali et al. compared serum CA-125 levels three months after laparoscopy in 16 women diagnosed with endometriosis and 12 women without. In women with endometriosis, there was a 198.3% difference in CA-125 levels between menses and mid-cycle days 10-15, compared with a 22% difference in women with no endometriosis (p<0.001)8. These authors suggested that this difference could be used as a diagnostic tool - a sensitivity of 93% and specificity of 92% for the diagnosis of endometriosis was achieved, using a threshold of an 83% increase in CA-125 during menses.

Our cases are an important addition to the literature regarding raised serum CA-125 levels in women with endometriosis. The high levels found during menstruation can cause unnecessary concern for patients, and their doctors. We recommend that CA-125 testing in women with suspected endometriosis be performed outside the menstrual phase of the cycle.

Conflicts of Interest
The authors have no conflicts of interest to declare.

Dr. David Crosby MB BCh MAO, MRCPI, MRCOG, Merrion Fertility Clinic, 60 Mount Street, Dublin 2
Tel: 353 1 663500
E mail:

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