Beyond Inflammatory Ratios: Age and CRP as Key Predictors of Re-Amputation in Diabetic Foot Patients

Abstract

Background and Objectives: Re-amputation is an important adverse outcome of diabetic foot disease. This study compared age and preoperative inflammatory parameters between patients with and without subsequent re-amputation and examined their adjusted associations with re-amputation group membership. Materials and Methods: The records of 206 patients treated between 2013 and 2024 were reviewed retrospectively, with 103 patients included in each group. Laboratory parameters obtained before the index amputation were analyzed in both groups. Between-group comparisons were performed using the Mann–Whitney U test. Three exploratory binary logistic regression models included age and C-reactive protein (CRP), together with the neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), or platelet-to-lymphocyte ratio (PLR). The regression and ROC analyses were based on 197 complete cases. Results: Patients in the re-amputation group were older and had higher WBC, neutrophil, monocyte, CRP, NLR, MLR, and PLR values and lower lymphocyte values. In the primary model, age (adjusted OR = 1.034, 95% CI: 1.010–1.058; p = 0.006) and CRP (adjusted OR = 1.006 per 1 mg/L, 95% CI: 1.003–1.010; p = 0.001) were independently associated with re-amputation group membership, whereas NLR was not (p = 0.834). Neither MLR (p = 0.176) nor PLR (p = 0.446) was independently associated in the alternative models. Individual-marker AUCs ranged from 0.604 to 0.647, indicating limited discrimination. Conclusions: Older age and higher pre-index-amputation CRP levels were independently associated with membership in the re-amputation group. Although NLR, MLR, and PLR differed between groups, these ratios were not independently associated after adjustment for age and CRP. The limited discriminatory performance and data-derived cutoff values require validation in larger, independent cohorts.