The infected diabetic foot: Can serum biomarkers predict osteomyelitis after hospital discharge for diabetic foot infections?

The aim of this study is to evaluate serum biomarkers to monitor high-risk patients for reinfection of bone. Thirty-five patients were prospectively enrolled with moderate to severe diabetic foot infections with suspicion of osteomyelitis. Bone samples were obtained for culture and histology. Clinical characteristics and outcomes of patients were compared using χ² square test. Biomarkers (white blood cell count, erythrocyte sedimentation rate, c-reactive protein, procalcitonin, interleukin-6, interleukin-8, and monocyte chemoattractant protein 1) were assessed at baseline, 3, and 6 weeks after treatment initiation and evaluated for correlation with reinfection of bone. After 6 weeks of antibiotic treatment, ESR at 73.5 mm/h (sensitivity 62.5%, specificity 100%, area under the receiver operating characteristic (AUROC) 0.7839, 95% CI 0.54-1.00, P < .01) and IL-8 at 15.09 mg/dL (sensitivity 42.9%, specificity 92.0% AUROC 0.6286, 95% CI 0.36-0.90, P = .0496) were associated with reinfection of bone. An increase in IL-8 from week 0 to 6 >0.95 mg/dL was associated with reinfection (sensitivity 71%, specificity 72% AUROC 0.7057, 95% CI 0.49-0.92, P = .04). An ESR change from week 0-6 of -16.5% (sensitivity 71.4%, specificity 86.4% AUROC 0.7403, 95% CI 0.48-1.00, P = .02), CRP (-)74.4% (sensitivity 66.7%, specificity 91.3% AUROC 0.7174, 95% CI 0.40-1.00, P = .04), IL-6 (-)49.9% (sensitivity 71.4%, specificity 76% AUROC 0.7371, 95% CI 0.47-1.00, P = .04), and IL-8 29% (sensitivity 85.7%, specificity 56.0% AUROC of 0.7343, 95% CI 0.54-0.93, P = .048) were associated with increased risk of reinfection. Pilot data suggest that serum biomarkers (ESR, IL8 and IL6, MCP-1) may be correlated with developing osteomyelitis and could be used to monitor high-risk patients for reinfection.

Comparison Between Tc-99m WBC SPECT/CT and MRI for the Diagnosis of Biopsy-proven Diabetic Foot Osteomyelitis

OBJECTIVE

Magnetic resonance imaging (MRI) is the recommended diagnostic imaging technique for diabetic foot osteomyelitis (DFO), with a reported accuracy of 79%. The gold standard to diagnose osteomyelitis is bone biopsy, with a positive culture and/or histopathology findings consistent with osteomyelitis. The purposes of this study are to assess the accuracy of technetium-99m (Tc-99m) labeled white blood cell (WBC) single-photon emission computed tomography/computed tomography (SPECT/CT) hybrid imaging for diagnosing DFO confirmed by bone biopsy and to compare that to the diagnostic accuracy of an MRI.

MATERIALS AND METHODS

The authors performed a retrospective chart review of 166 patients who received a bone biopsy to confirm the diagnosis of a suspected DFO at a large municipal hospital between 2010 and 2013. Patients were selected on the basis of whether they received an MRI or a SPECT/CT. Patients whose scans were not within a clinically relevant time frame of the biopsy were excluded. Imaging results were correlated with probability of osteomyelitis determined by bone biopsy.

RESULTS

For inclusion criteria, 110 patients met the study's criteria: 52 SPECT/CT patients and 58 MRI patients. The sensitivity, specificity, positive predictive value, and negative predictive value of SPECT/CT were 89%, 35%, 74%, and 60%, respectively; the corresponding values for MRI were 87%, 37%, 74%, and 58%, respectively. There were no significant differences in accuracy of diagnosing DFO between imaging techniques.

CONCLUSION

This data suggests that the diagnostic accuracy of SPECT/CT imaging in DFOs is similar to an MRI.