Association between thyroid feedback quantile‐based index and the risk of in‐hospital amputation in patients with diabetic foot ulcer

Aims To investigate the relationship between the thyroid feedback quantile‐based index (TFQI) and the risk of amputation during hospitalization in patients with diabetic foot ulcers (DFU). Methods This single‐center retrospective study included 381 hospitalized patients with DFU and normal thyroid function. Logistic regression assessed continuous TFQI and quartiles. Model 1 was unadjusted; Model 2 adjusted for age, sex, BMI, and smoking; Model 3 additionally adjusted for diabetes duration, HbA1c, diabetic peripheral neuropathy, peripheral arterial disease, hypertension, CRP, and dyslipidemia. RCS assessed dose–response patterns; Firth regression was used for sensitivity analysis. Results Fifty‐six patients underwent amputation. In Model 3, each 1‐SD increase in TFQI (equivalent to a 1‐unit increase in pre‐scaled TFQI) was associated with higher odds of amputation (OR 2.27, 95% CI 1.63–3.15; P < 0.001). Compared with Q1, ORs were 2.94 (0.98–8.83; P = 0.055), 5.60 (1.88–16.67; P = 0.002), and 14.79 (5.22–41.89; P < 0.001) for Q2, Q3, and Q4, respectively. RCS showed an overall association ( P = 0.002) and nonlinearity ( P = 0.046) in Model 3. Firth estimates were broadly consistent with conventional regression. Conclusion Among hospitalized DFU patients with normal thyroid function, higher TFQI levels are associated with an increased risk of amputation during hospitalization. Nevertheless, the clinical utility of TFQI requires further validation in prospective studies.