Discriminative Performance of the C-Reactive Protein-Triglyceride-Glucose Index for Endometriosis: A Case-Control Study

INTRODUCTION: Endometriosis, a common gynecologic disorder, causes pain and fertility problems. Since laparoscopy, as a definitive diagnostic procedure, is considered invasive, finding reliable and noninvasive biomarkers is a clinical priority. This study evaluated the diagnostic performance of C-reactive protein-triglyceride-glucose index (CTI) for endometriosis. MATERIALS AND METHODS: In this case-control study, 153 participants with surgically confirmed endometriosis and 112 participants without visible endometriosis at laparoscopy were included. Fasting glucose, triglycerides (TG), total cholesterol, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) were measured, and CTI was calculated using a previously described formula. Receiver operating characteristic (ROC) analysis was carried out to assess diagnostic discrimination and identify an exploratory threshold for CTI cutoff. Multivariable logistic regression was used to assess the independent relationship between CTI and endometriosis. Nested models were also assessed to examine the incremental contribution of TG and glucose beyond CRP. RESULTS: Women with endometriosis exhibited higher levels of TG, total cholesterol, ESR, CRP, and CTI than controls (all P<0.001), whereas fasting glucose did not differ significantly between groups. CTI showed good discrimination for endometriosis, with an area under the ROC curve (AUC) of 0.900 (95% CI, 0.858-0.942). An exploratory cutoff of 9.686 yielded a sensitivity of 92.16% and specificity of 83.93%. CTI was independently associated with endometriosis after adjustment for age, body mass index, systolic and diastolic blood pressure (adjusted OR per 0.5-unit increase, 2.598; 95% CI, 2.079-3.245; P<0.001). However, CTI's discriminatory performance was not significantly different from CRP's. (AUC 0.898; P=0.827). Addition of TG to a CRP-based model significantly improved model fit (P=0.007), whereas addition of glucose did not (P=0.095); the overall difference in AUCs across the nested models was not statistically significant (P=0.719). CONCLUSION: CTI showed good discrimination for endometriosis but did not significantly outperform CRP. It may serve as a complementary biomarker alongside clinical and imaging assessment.