Cross-sectional associations and incremental discrimination of inflammatory and lipid-derived indices for prevalent coronary heart disease in type 2 diabetes

Background Routine blood-count and lipid-derived indices may be associated with coronary heart disease (CHD) in type 2 diabetes mellitus (T2DM), but comparative evidence within one cohort is limited. Methods This cross-sectional study included 3,964 adults with T2DM. Six inflammatory and three lipid-derived indices were examined using quartile-based and standardized continuous logistic regression. Domain-specific covariate sets avoided adjustment for constituent lipids. Dose–response, subgroup, and temporal sensitivity analyses were performed. Incremental discrimination was assessed against a common clinical base model with bootstrap optimism correction. Calibration and decision curves were based on cross-validated estimated probabilities; high-sensitivity C-reactive protein was a benchmark. Results CHD was present in 1,350 participants (34.1%). Median SII was 649 × 10 9 /L in participants with CHD and 522 × 10 9 /L in those without CHD ( P < 0.001). The adjusted OR for SII was 2.37 (95% CI, 1.91–2.93) for Q4 versus Q1 and 1.46 (95% CI, 1.36–1.58) per 1-SD increase. The association was nonlinear ( P for nonlinearity < 0.001), with no interaction by sex, age, BMI, or hypertension. The optimism-corrected AUC increased from 0.729 to 0.744 after adding SII (ΔAUC = 0.015, P < 0.001); corrected AUCs were 0.744 for PIV and 0.745 for SIRI. Paired comparisons showed no statistically significant difference between the SII-augmented model and either the PIV-augmented model (P = 0.964) or the SIRI-augmented model (P = 0.717). The SII model showed a cross-validated AUC of 0.742, Brier score of 0.188, ICI of 0.017, and calibration slope of 0.963. Conclusion Several indices were associated with prevalent CHD, without consistent evidence that SII was superior.