The Positive Association Between RCII and Endometriosis and Its Integration into a Clinical Predictive Model: A Cross-Sectional Study

Introduction: Studies indicate that endometriosis (EMs) is associated with inflammation and metabolic abnormalities. The Remnant Cholesterol Inflammatory Index (RCII) concurrently reflects both inflammatory and metabolic status. However, the relationship between RCII and EMs remains unclear. Therefore, this study aims to investigate the association between RCII and EMs and explore the potential of RCII as a risk predictor for EMs. Methods: Making use of information from the 1999-2006 NHANES database, we investigated the connection between natural logarithm-transformed RCII (lnRCII) and EMs employing logistic regression analysis, restricted cubic spline (RCS) models, and subgroup analysis approaches. Finally, a nomogram was constructed based on feature variables selected via LASSO regression to enhance the interpretability of the predictive model. Results: After adjusting for potential confounding factors, lnRCII demonstrated a substantial positive correlation with the risk of EMs. For each 1-standard-deviation increase in lnRCII, the EMs' risk increased by 25% (fully adjusted model OR = 1.250, 95% CI: 1.266-1.461, P = 0.006). Furthermore, a linear relationship between lnRCII and EMS was observed via RCS analysis. According to subgroup analysis, the relationship between lnRCII and EMS has a consistent association across the majority of the population. (P for interaction > 0.05). Conclusion: In the US population, RCII was substantially linked to a higher risk of EMs, suggesting that the lipid metabolism-inflammation axis may represent a potential target for intervention in the prevention or treatment of EMs.