Triglyceride–glucose index and triglyceride/HDL-cholesterol ratio versus HbA1c and HOMA-IR for identifying microvascular complications in type 2 diabetes: a cross-sectional comparative diagnostic accuracy study from Western India

Insulin resistance contributes to microvascular complications of type 2 diabetes, but HOMA-IR requires insulin measurement. The triglyceride–glucose (TyG) index and triglyceride/HDL-cholesterol (TG/HDL-C) ratio are insulin-free surrogates using routine fasting biochemistry. We compared their discrimination with HbA1c and HOMA-IR for identifying prevalent microvascular complications. We conducted a cross-sectional comparative diagnostic accuracy study at a tertiary-care hospital in Pune, western India, enrolling 110 adults with type 2 diabetes. The prespecified composite outcome comprised diabetic retinopathy, kidney disease and peripheral neuropathy, with per-component analyses. Discrimination was assessed by AUC with DeLong confidence intervals; six pairwise comparisons used DeLong’s test with Holm–Bonferroni adjustment. Youden cut-offs were exploratory. Multivariable associations used Firth’s penalised-likelihood regression; calibration, decision curve analysis and incremental value (NRI, IDI) were also assessed. Among 110 participants, 64 (58.2%) had at least one microvascular complication. TyG achieved an AUC of 0.993 (95% CI 0.984–1.000), followed by HbA1c 0.971, TG/HDL-C 0.959 and HOMA-IR 0.810. TyG, TG/HDL-C and HbA1c each outperformed HOMA-IR (adjusted p < 0.001), with no significant differences among the three. The exploratory cut-offs were TyG ≥ 9.23 and TG/HDL-C ≥ 3.40; TyG had 93.8% sensitivity and 100% specificity at its cut-off. Each one-SD rise in TyG and TG/HDL-C remained associated with the outcome after Firth penalisation ( p = 0.002 and 0.003). Calibration was assessed using the intercept, slope and Brier score; adding TyG to a base HbA1c-plus-HOMA-IR model gave an IDI of 0.219. TyG and TG/HDL-C identified prevalent microvascular complications with discrimination at least comparable to HbA1c and above HOMA-IR. The unusually high AUCs may reflect the tertiary-care disease spectrum and should be regarded as upper bounds. Exploratory cut-offs require prospective, multicentre external validation before triage use; this cross-sectional study makes no claim of predictive or screening performance. Not applicable; observational cross-sectional study.