The Classic TyG Index Outperforms Neck-Based Variants for Detecting Metabolic Syndrome in Metabolic Bariatric Surgery Candidates

Abstract Objective To compare the diagnostic performance of TyG-NC and TyG-NHtR with the classic TyG index for identifying MetS in bariatric surgery candidates. Methods Cross-sectional diagnostic test study using secondary data from adults evaluated at a bariatric clinic. MetS was defined according to Latin American Diabetes Association criteria. Diagnostic accuracy was assessed using AUC-ROC curves with 95% confidence intervals (95%CI). Optimal cut-off points were identified using Liu’s method with 1000 bootstrap replications. Associations with MetS were evaluated using Poisson regression models with robust variance to estimate prevalence ratios. Results Among 349 adults (67.1% women; mean age 34.9 ± 9.7 years; median BMI 37.3 kg/m²), the classic TyG index evidenced higher discrimination for MetS (AUC 0.86, 95%CI: 0.82–0.90) than TyG-NC (0.72, 95%CI: 0.67–0.77) or TyG-NHtR (0.73, 95%CI: 0.67–0.78). TyG values above 8.8 were strongly associated with MetS (aPR = 3.39, 95%CI: 2.60–4.43), outperforming TyG-NC (aPR = 1.86, 95%CI: 1.47–2.35) and TyG-NHtR (aPR = 1.76, 95% CI: 1.39–2.24). Performance remained consistent across sex-stratified analyses. Conclusions In Peruvian bariatric patients, the classic TyG index outperformed its neck-based variants for identifying MetS. When central adiposity and metabolic disturbances are already marked, adding neck circumference may offer limited additional value beyond triglycerides and glucose.