Nonlinear association between C-reactive protein and severity of diabetic foot infection in patients with diabetes: A retrospective cohort study with clinical implications.

Objective: Diabetic foot infection(DFI) is a frequent complication of diabetes and can lead to significant morbidity and mortality. These are huge economic health burdens for patients, countries, and the world. Timely diagnosis and accurate assessment of the severity of DFI based on sensitive inflammatory biomarkers is critical, with considerable benefits for debridement procedures and antibiotic use. This study aimed to examine the association between C-reactive protein (CRP) levels and the severity of DFI in patients with diabetes.

Methods: In this retrospective cohort study, we investigate the association between CRP levels and the severity of DFI in patients with diabetes. Multivariable logistic regression modeling, a generalized additive model, and a two-piecewise linear regression model were conducted to explore the relationship between CRP levels and DFI severity.

Results: Based on inclusion exclusion criteria, A total of 301 patients with Wagner stage 3 or higher diabetic foot ulcers combined with moderate to severe infections were included in the study at last. CRP levels were independently associated with the severity of DFIs after accounting for potential confounding factors. A nonlinear relationship was observed between CRP level and DFI severity, with a threshold of approximately 105 mg/L. The odds ratio for severe diabetic foot infection was 1.039 (95% confidence interval: 1.019-1.06, P < 0.001) in patients with DFI and CRP < 105 mg/L.

Conclusion: The relationship between CRP and the severity of DFI was nonlinear; as CRP levels remained below 105 mg/L, the severity of DFI increased with an increase in CRP.