Comparing diagnostic accuracy of F-FDG-PET/CT, contrast enhanced CT and combined imaging in patients with suspected vascular graft infections

Abstract

BACKGROUND To evaluate the diagnostic accuracy of positron emission tomography/computed tomography with F-fluorodeoxyglucose (PET/CT), contrast-enhanced CT (CE-CT), and a combined imaging approach (CE-PET/CT) in patients with suspected vascular graft infection (VGI).
METHODS PET/CT and CE-CT were performed prospectively in 23 patients with suspected VGI. Diagnostic accuracy for PET/CT was assessed by using previously suggested cut-off points for maximum standardized uptake values (SUV) measured in the vicinity of the graft. Using a new 4-point scale for visual grading, two readers independently assessed the diagnostic accuracy for CE-CT and combined CE-PET/CT. Microbiological culture, obtained after open biopsy or graft explantation, and clinical follow-up of the patients served as the standard of reference.
RESULTS Sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), and accuracy of PET/CT for the diagnosis of VGI was 100%, 50%, 100%, 72.2%, and 78.3%, using the most favorable SUV cut-off ≥ 4.9. Respective values for CE-CT were 100%, 50%, 100%, 72.2%, and 78.3% for reader 1, and 92.3%, 80%, 88.9%, 85.7%, and 86.9% for reader 2; while respective values for combined CE-PET/CT were 100%, 70%, 100%, 81.3%, and 86.9% for reader 1, and 100%, 80%, 100%, 86.7%, and 91.3% for reader 2. Additionally, imaging provided a conclusive clinical diagnosis in patients without graft infection (i.e., other sites of infection): five of ten patients with CE-CT, six of ten patients with PET/CT, and seven of ten patients with combined CE-PET/CT.
CONCLUSION The diagnostic accuracy of combined CE-PET/CT in patients with suspected VGI is very high. The combination of the high sensitivity of PET/CT in detecting metabolically active foci in infection, and the high specificity of CE-CT in detecting anatomic alterations, appears to be the reason why combined imaging outperforms stand-alone imaging in diagnosing VGI and may be supportive in future decision-making of difficult cases of suspected VGI. Clinical Trials.gov Identifier: NCT01821664.