SLR - November 2021 - Jeff D. Tucci

Comparison of White Blood Cell Scintigraphy, FDG PET/CT and MRI in Suspected Diabetic Foot Infection: Results of a Large Retrospective Multicenter Study

Reference: Lauri C, Glaudemans AWJM, Campagna G, et al. Comparison of White Blood Cell Scintigraphy, FDG PET/CT and MRI in Suspected Diabetic Foot Infection: Results of a Large Retrospective Multicenter Study. J Clin Med. 2020;9(6):1645. Published 2020 May 30. doi:10.3390/jcm9061645

Level of Evidence: Level III

Scientific Literature Review

Reviewed By: Jeff D. Tucci, DPM
Residency Program: Hennepin Healthcare – Minneapolis, MN

Podiatric Relevance: This study aims to compare the accuracy of white blood cell (WBC) scintigraphy, F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT), and Magnetic Resonance Imaging (MRI) in differentiating osteomyelitis, soft tissue infection, and Charcot in patients with suspected diabetic foot infection (DFI). Currently there is no clear consensus on the most appropriate imaging techniques to use in suspected DFI patients. Additionally, improving the accuracy and efficiency of diagnosis has the potential to improve patient outcomes and guide appropriate treatment plans.  

Methods: This was a retrospective analysis of imaging data from a multi-center study for patients with diabetic foot complications between 2008 and 2014. Inclusion criteria: Type 1 or Type 2 diabetes on oral medications or insulin, suspected DFI on clinical presentation, at least one of three imaging modalities performed, and final diagnosis provided by gold standard (biopsy). Exclusion criteria: inconclusive biopsy results or patients lost to clinical follow up. Images were read by experienced radiologists, blinded to final diagnoses. Software statistical analysis was used to calculate sensitivity, specificity, and accuracy of WBC, FDG, and MRI in diagnosing osteomyelitis (OM), soft tissue infection (STI), and Charcot osteoarthropathy.

Results: There were 251 patients enrolled in the study from five contributing centers. Ninety-three patients were diagnosed via gold standard with OM, 76 with STI, and 10 with Charcot. In OM, WBC scintigraphy was shown to be more specific and accurate than MRI (91.9 percent vs. 70.7 percent, p<0.0001 and 86.2 percent vs. 67.1 percent, p= 0.003). In STI, both FDG PET/CT and WBC scintigraphy had significantly higher specificity than MRI (97.9 percent and 95.7 percent vs. 83.6 percent, p= 0.04 and p= 0.018). In Charcot, both MRI and WBC scintigraphy demonstrated significantly higher specificity and accuracy than FDG PET/CT (88.2 percent and 89.3 percent vs. 62.5 percent, p= 0.0009; 80.3 percent and 87.9 percent vs. 62.1 percent, p< 0.02). WBC scintigraphy was shown to be the most reliable imaging modality to differentiate between OM, STI, and Charcot in patients with suspected DFI.

Conclusions: The authors conclude that WBC scintigraphy is superior to other imaging modalities in accuracy, specificity, and sensitivity in discriminating OM, STI, and Charcot when proper imaging guidelines are followed. Using WBC scintigraphy from a practical standpoint involves several considerations, including economics, access, and infrastructure. Use on every suspected DFI in busy clinics with limited resources or areas without proper infrastructure may be ill-advised. A particular application of value I can see for use of WBC scintigraphy is in the case of Charcot osteoarthropathy with possible concomitant osteomyelitis present. Before undertaking a lengthy and expensive Charcot reconstructive procedure it would be beneficial to rule out any variables that could potentially compromise a patient’s outcome. 

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