Association between the CRP–triglyceride–glucose index and chronic obstructive pulmonary disease: A cross-sectional study based on NHANES 2015 to 2018

Chronic obstructive pulmonary disease (COPD) is a leading cause of global mortality and has been linked to systemic inflammation and insulin resistance. The C-reactive protein-triglyceride-glucose index (CTI), a composite biomarker integrating inflammatory and metabolic components, may reflect these intertwined pathways. However, its association with COPD in the general population remains unclear. In this cross-sectional study, we analyzed data from 3442 adults aged ≥20 years participating in the National Health and Nutrition Examination Survey 2015 to 2018. Weighted multivariable logistic regression models were used to assess the association between CTI and self-reported COPD. Dose-response relationships were evaluated using restricted cubic splines. Subgroup and interaction analyses were performed across demographic and socioeconomic factors. Receiver operating characteristic (ROC) curves were constructed to compare the discriminatory ability of CTI with individual biomarkers. Mean CTI levels were higher among participants with COPD compared to those without COPD (9.29 vs 8.95; P < .001). After adjustment for potential confounders, participants in the highest CTI quartile had a modestly increased likelihood of COPD compared with those in the lowest quartile (odds ratio = 1.04, 95% confidence interval: 1.02-1.07). A linear dose-response association was observed (P for nonlinearity = .319). A statistically significant interaction by sex was identified, with a stronger association observed in males. In ROC curve analysis, CTI demonstrated slightly higher discriminatory ability (area under the ROC curve = 0.630) than individual biomarkers, although overall predictive performance remained limited. In this nationally representative cross-sectional analysis, higher CTI levels were independently associated with COPD prevalence, with a modest effect size. While CTI showed slightly improved discriminatory performance compared with single biomarkers, its overall predictive capacity was limited. Prospective studies are warranted to clarify its potential role in COPD risk assessment.