Association between the C-reactive protein–triglyceride–glucose index and in-hospital minor amputation in diabetic foot ulcers

Background The C-reactive protein–triglyceride–glucose index (CTI) is a composite biomarker reflecting systemic inflammation and insulin resistance. CTI has been studied in diabetic foot with respect to mortality; whether it is associated with in-hospital minor amputation has not been examined. This study aimed to assess the association of CTI with in-hospital minor amputation in patients with diabetic foot ulcers (DFU). Methods We carried out a retrospective analysis involving 585 patients diagnosed with type 2 diabetes and DFU, comprising 479 cases without amputation and 106 cases with minor amputation. Statistical approaches included univariate and multivariable logistic regression, tertile-based analyses, restricted cubic splines (RCS), ROC curve analysis with DeLong tests, comparisons of nested models, and internal validation using bootstrap resampling along with calibration plots, calibration slope/intercept, and Brier score assessments. Results Patients who underwent in-hospital minor amputation exhibited higher CTI values (10.99 [10.57–11.43] vs. 10.30 [9.51–10.98]; p < 0.001). The incidence of amputation escalated from 6.2% in T1 to 19.4% in T2 and further to 28.9% in T3; compared with T1, the adjusted odds ratio was 2.742 (95% CI 1.284–5.859) for T2 and 3.081 (95% CI 1.442–6.583) for T3 (adjusted p for trend = 0.007). The adjusted RCS analysis corroborated an approximately linear relationship (adjusted p-nonlinearity = 0.293). In the prespecified multivariable model, CTI remained independently associated with in-hospital minor amputation (adjusted OR = 1.844, 95% CI 1.344–2.529, p < 0.001). Discriminative performance of the models improved progressively (Model 1 with CTI alone: AUC 0.718; Model 3: 0.835, optimism-corrected 0.817). Conclusions In this single-center retrospective cohort, elevated admission CTI was associated with increased odds of in-hospital minor amputation and provided modest incremental discrimination beyond a prespecified clinical model. CTI may represent a candidate biomarker in this setting, but its clinical applicability requires external prospective validation.