A researcher group conducted a meta-analysis to assess the sensitivity and specificity of cancer antigen (CA) 125 in the diagnosis of endometriosis, and found that CA 125 was a highly specific, but not highly sensitive, diagnostic method in endometriosis.
Endometriosis, the presence of uterine tissue outside of the uterus, affects 75% of symptomatic women. Despite the high prevalence, endometriosis is really under-diagnosed, mainly because the only diagnostic method is an invasive one: taking tissue out of the body and examining it. Researchers are on the lookout for new non-invasive diagnostic methods that may reduce time to diagnosis and psychological stress for women and lead to a more personalized treatment. Cancer antigen 125 (CA 125, a protein found on many ovarian cancer cell surfaces) is the most investigated biomarker that may be effective in the diagnosis of endometriosis.
A meta-analysis was published recently in BJOG: An International Journal of Obstetrics and Gynaecology that included 22 studies with 3626 participants. Fourteen studies with 2920 participants were meta-analysed for the sensitivity and specificity of >30 units/ml CA 125 in the diagnosis of endometriosis. Individual study sensitivities ranged from 0% to 87% and specificity from 51% to 100%. The pooled sensitivity of >30 units/ml CA 125 was 52.4%, while the specificity was 92.7%. Furthermore, the sensitivity of CA 125 was higher with a more severe disease. It seems that a positive result means endometriosis, but a negative one might not mean the absence of the disease.
In conclusion, CA 125 is a highly specific diagnostic method for endometriosis. However, a <30 units/ml CA 125 result does not mean that there is no endometriosis and further investigation is needed to find biomarkers that are able to diagnose endometriosis with a higher sensitivity.
Written By: Dr. Fanni R. Eros