Diagnostic accuracy of C-reactive protein for diabetic foot osteomyelitis: a retrospective study and meta-analysis of composite cut-off values

OBJECTIVE: To determine the composite cut-off value and diagnostic accuracy of C-reactive protein (CRP) for diabetic foot osteomyelitis (DFO). METHOD: A retrospective study of patients was combined with a meta-analysis. Study quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. Pooled sensitivity, specificity and area under the curve (AUC) were calculated via forest plots and summary receiver operating characteristic curves. A composite cut-off model was developed using R 4.4.3 (R Foundation for Statistical Computing, Austria). RESULTS: The experimental cohort comprised 265 patients (204 with DFO and 61 without). The meta-analysis comprised 12 studies, including a total of 1828 patients. The retrospective cohort demonstrated that CRP achieved an AUC of 0.63 (95% confidence interval (CI): 0.55, 0.71) for diagnosing DFO, with an optimal cut-off value of 9.57mg/l (sensitivity 74%, specificity 53%). Meta-analysis revealed pooled sensitivity of 74% (63-83%) and specificity of 73% (65-79%) (AUC=0.79; 95%CI: 0.75, 0.82). The composite model suggested a CRP cut-off of 15.20mg/l (sensitivity 80%, specificity 53%). CONCLUSION: In this study, CRP demonstrated moderate diagnostic utility for DFO and could function as a screening adjunct.