The role of triglycerides and HDL in predicting insulin resistance in diabetic and non-diabetic young adults in Lephalale, Limpopo Province, South Africa

Insulin resistance (IR) drives early cardiometabolic risk in low-resource settings, yet gold-standard measures are impractical. We assessed routine lipids, triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and the TG/HDL-C ratio, as predictors of IR in 781 adults aged 20–29 years from the Ellisras Longitudinal Study (Lephalale, Limpopo). IR was defined as HOMA-IR ≥2.5. Participants were 51.8% female and 39.1% diabetic. Diabetic participants showed higher fasting glucose, insulin, and HOMA-IR, and more adverse lipid profiles than non-diabetics (all p < 0.001). Receiver-operating-characteristic analysis showed the TG/HDL-C ratio discriminated IR best (AUC 0.88, 95% CI 0.85–0.91), outperforming TG (0.78, 0.74–0.82) and HDL-C (0.75, 0.71–0.79). A practical cut-off of ≥2.0 yielded 82.1% sensitivity and 85.0% specificity. In multivariable models adjusted for age and sex, TG ≥1.7 mmol/L (aOR 2.92, 95% CI 2.04–4.18), low HDL-C (AOR 2.47, 1.75–3.48), and TG/HDL-C ≥ 2.0 (aOR 4.85, 3.32–7.08) were independently associated with IR; each year of age increased odds (AOR 1.06), and sex was not significant. Performance was consistent across diabetes status (AUC 0.84 non-diabetic; 0.81 diabetic) and sex (0.86 males; 0.83 females). The TG/HDL-C ratio is a simple, low-cost screening tool for IR in semi-rural South Africa and merits integration into primary care.