Evaluation of Neutrophil-to-Lymphocyte Ratio and CRP-to-Albumin Ratio in the Risk Stratification of Diabetic Foot Infection Severity

Background: Diabetic foot ulceration represents one of the most severe diabetic complications, with 50–60% progressing to diabetic foot infection (DFI). All diabetic wounds and diseases originate from peripheral vasculopathy and neuropathy, which are caused by oxidative stress and inflammatory processes. We investigated the utility of neutrophil-to-lymphocyte ratio (NLR) and CRP-to-albumin ratio (CAR) as cost-effective inflammatory biomarkers in DFI. Methods: The study included 58 DFI patients and 45 healthy controls. Disease severity was assessed using PEDIS staging. Routine laboratory parameters, NLR, derived NLR (d-NLR), and CAR were measured and compared. Results: In DFI patients, statistically significant increases (p < 0.001) were observed in NLR (3.12 vs. 1.99, p < 0.001), d-NLR (2.13 vs. 1.49, p = 0.003), CAR (0.91 vs. 0.03, p < 0.001), CRP (30.5 vs. 1.3 mg/L, p < 0.001) and PCT (0.1 vs. 0.02 μg/L, p < 0.001) values compared to the control group. Strong correlations existed between NLR, CAR and disease severity markers (CRP, PCT, HbA1c, osteomyelitis, PEDIS stage). ROC analysis revealed excellent discriminatory power for CAR (AUC = 0.915), PCT (AUC = 0.952), and CRP (AUC = 0.902), while NLR showed moderate performance (AUC = 0.702). Conclusions: NLR/CAR demonstrate excellent discrimination vs. healthy controls (AUC 0.915/0.702). The proposed workflow (NLR screening → CAR severity → PCT confirmation) requires prospective validation against with guidelines.