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

Abstract

Diabetic foot infections (DFIs) represent one of the most frequent and disabling morbidities of longstanding diabetes; therefore, early diagnosis is mandatory. The aim of this multicenter retrospective study was to compare the diagnostic accuracy of white blood cell scintigraphy (WBC), 18F-fluorodeoxyglucose positron emission tomography/computed tomography ((18F) FDG PET/CT), and Magnetic Resonance Imaging (MRI) in patients with suspected DFI. Images and clinical data from 251 patients enrolled by five centers were collected in order to calculate the sensitivity, specificity, and accuracy of WBC, FDG, and MRI in diagnosing osteomyelitis (OM), soft-tissue infection (STI), and Charcot osteoarthropathy. In OM, WBC acquired following the European Society of Nuclear Medicine (EANM) guidelines was more specific and accurate than MRI (91.9% vs. 70.7%, p < 0.0001 and 86.2% vs. 67.1%, p = 0.003, respectively). In STI, both FDG and WBC achieved a significantly higher specificity than MRI (97.9% and 95.7% vs. 83.6%, p = 0.04 and p = 0.018, respectively). In Charcot, both MRI and WBC demonstrated a significantly higher specificity and accuracy than FDG (88.2% and 89.3% vs. 62.5%, p = 0.0009; 80.3% and 87.9% vs. 62.1%, p < 0.02, respectively). Moreover, in Charcot, WBC was more specific than MRI (89.3% vs. 88.2% p < 0.0001). Given the limitations of a retrospective study, WBC using EANM guidelines was shown to be the most reliable imaging modality to differentiate between OM, STI, and Charcot in patients with suspected DFI.

Diabetic Foot Infections: The Diagnostic Challenges

“…In accordance with this view, we strongly recommend the use of radiolabelled WBC scintigraphy in suspected pedal OM, as it also emerged from a recently published retrospective multicenter study [89].…”

“…In accordance with this view, we strongly recommend the use of radiolabelled WBC scintigraphy in suspected pedal OM, as it also emerged from a recently published retrospective multicenter study [ 89 ]. [ 18 F]FDG PET/CT could represent a valid alternative if it is not possible to perform this imaging modality due to the limitations of the single center, but the interpretation of a PET scan, at the moment, really relies on personal experience, and therefore, the scans must be evaluated with caution.…”

Handling of Doubtful WBC Scintigraphies in Patients with Suspected Prosthetic Joint Infections

“…The recently published EANM guidelines have definitely clarified all the aspects able to reach a high accuracy in detecting an infection by using this imaging modality [ 15 ]. Indeed, if correctly acquired, displayed and interpreted, planar images allow to accurately differentiation between an infection from a sterile inflammation, as it has also been demonstrated in other clinical scenarios [ 24 ]. However, despite these precautions, some scintigraphies still remain doubtful basing only on visual analysis.…”

PET/CT Imaging for Personalized Management of Infectious Diseases

“…PET-tracers can also be used to label leukocytes. Because labelled leukocytes require 20–24 h to be recruited to infection sites, FDG is not suitable for radiolabeling glucose due to its short half-life [ 56 ].…”