Assessing diabetic foot osteomyelitis remission with white blood cell SPECT/CT imaging

Aims Diabetic foot osteomyelitis is an important risk factor of lower limb amputation. Antibiotic therapy is often effective in preventing surgery. However, the duration of antibiotic therapy is difficult to define in the absence of a marker to diagnose osteomyelitis remission at the end of the treatment. In this study, we assessed the diagnostic performance of white blood cell SPECT/CT imaging for evaluating osteomyelitis remission. Patients and methods Twenty-nine out of 42 episodes of diabetic foot osteomyelitis seen between December 2009 and April 2012 had radiographs, a three-phase bone scintigraphy and a white blood cell SPECT/CT at the end of antibiotic therapy. They were treated with antibiotics alone and considered in clinical remission. White blood cell SPECT/CT results were considered positive when abnormal uptake in the osteomyelitis location was identified. Osteomyelitis remission was defined by the absence of an osteomyelitis relapse after 12 months' follow-up. Results A negative white blood cell SPECT/CT was seen for 22 episodes of osteomyelitis. All of them were in remission. A positive white blood cell SPECT/CT was observed for seven episodes. A relapse occurred in five episodes (71.5%) after a median duration of 4 months (2-7 months). Sensitivity, specificity, positive predictive value and predictive negative value in predicting osteomyelitis relapse after the discontinuation of antibiotic treatment were, respectively, for radiographs 80%, 33%, 20% and 89%; for three-phase bone scintigraphy 100%, 12.5%, 15.5% and 100%; and for the white blood cell SPECT/CT 100%, 91.5%, 71.5% and 100%. Conclusion Negative uptake on white blood cell SPECT/CT is a good marker for diagnosis of diabetic foot osteomyelitis remission and might be very useful in guiding antibiotic therapy.