Diagnostic Value of Erythrocyte Sedimentation Rate and C Reactive Protein in detecting Diabetic Foot Osteomyelitis; a Cross-sectional Study

INTRODUCTION: Osteomyelitis is one of the complications of diabetic foot infection. The present study aimed to evaluate the diagnostic value of erythrocyte sedimentation rate (ESR) and C reactive protein (CRP) in detection of osteomyelitis in patients with diabetic foot. METHODS: In this cross-sectional study, serum levels of ESR and CRP were measured for patients with diabetic foot referring to emergency department or endocrinology clinic and the screening performance characteristics of these markers in detection of osteomyelitis were calculated. The diagnosis of osteomyelitis was based on clinical examination and positive probe-to-bone test, which was confirmed by plain x-rays or MRI. RESULTS: 142 diabetic patients with an average age of 61.2 ± 11.8 years were evaluated (66.2 % male). The area under the ROC curve of ESR in detection of osteomyelitis in diabetic foot cases was 0.70 (95% CI: 0.62-0.79). The best ESR cut-off point in this regard was 49 mm/hour. Sensitivity, specificity, positive and negative predictive values, and positive and negative likelihood ratios of ESR in 49 mm/Hour cut-point were 74.6% (95% CI: 62.9-83.9), 57.7% (95% CI: 45.5-69.2), 63.9% (95% CI: 52.5-73.9), 69.5 % (95% CI: 56.0-80.0), 1.8 (95% CI: 1.3-2.4) and 0.4 (95% CI: 0.3-0.7), respectively. The area under the ROC curve of CRP in detection of osteomyelitis was 0.67 (95% CI: 0.58-0.76). The best cut-off point for CRP in this regard was 35 mg/liter with sensitivity, specificity, positive and negative predictive values, and positive and negative likelihood ratios of 76% (95% CI: 64.2-85), 54.9% (95% CI: 42.7-66.6), 62.8% (95% CI: 51.6-72.8), 69.6% (95% CI: 51.7-80.8), 1.7 (95% CI, 1.3-2.2), and 0.4 (95% CI: 0.3-0.7), respectively. CONCLUSION: Based on the findings of ROC curve analysis, ESR and CRP had fair and poor accuracy, respectively, in detecting the diabetic foot cases with osteomyelitis.