Objective: Endometriosis causes dysmenorrhea, pelvic pain and subfertility. Surgery is currently the only way of definitively diagnosing endometriosis; however, it is risky, costly and sometimes unnecessary. There is international recognition of the need for a non-invasive diagnostic test. The aim of this study was evaluating circulating microRNAs as diagnostic biomarkers for endometriosis.
Design and Methods: The study was divided into five phases: 1) verifying the stability of plasma microRNAs across the menstrual cycle; 2) biomarker discovery using multiplex Taqman Low Density Arrays (a) comparing women with endometriosis and healthy controls (n=8+8) and (b) comparing symptomatic women with and without surgically defined endometriosis (n=10+10); 3) a literature review to select promising microRNAs; 4) Singleplex RT-PCR validation of selected microRNAs in a small surgically defined cohort of women with pelvic pain (51 endometriosis and 27 endomretriosis-free) and 5) testing in an independent large surgically defined cohort of women with pelvic pain (74 endometriosis and 34 endometriosis-free).
Results: 61 microRNAs were selected for validation. After normalisation to miR30b, 6 microRNAs (miR574-3p, miR155, miR139-3p, miR923, miR668, and miR433) demonstrated significance and 6 more microRNAs showed a trend to significance. The first three microRNAs were validated in the large cohort as being significantly differentially regulated between two groups (p values = 0.031, 0.016 and 0.009, respectively). AUC was 0.72 in ROC analysis. At a cut-off of 0.612, the combination of the three microRNAs could distinguish endometriosis and control subjects with a sensitivity of 79% and a specificity of 51%.
Conclusions: Plasma microRNAs have been identified differentially expressed in endometriosis. Further validation is required, but at this stage, the sensitivity and specificity of the 3 tested mircoRNAs are not high enough for a replacement test for surgery. The diagnostic potential of these microRNAs could contribute to an accurate diagnostic test in combination with other biomarkers.