The utility of fluorine-18-fluorodeoxyglucose positron emission tomography in the diagnosis and monitoring of large vessel vasculitis: A South Australian retrospective audit

Aims To investigate the utility of fluorine-18-labelled deoxyglucose positron emission tomography (FDG-PET) in routine clinical practice to diagnose and monitor disease activity and treatment response in large vessel vasculitis in a South Australian cohort. Methods We performed a retrospective clinical audit of adult patients who received a FDG-PET at a tertiary referral center between August 2010 and August 2015, where the term "vasculitis" appeared in either the request or report. Results A total of 45 patients met the inclusion criteria. Nine patients (20%) had a positive FDG-PET for large vessel vasculitis. FDG-PET was positive in 3/6 (50%) patients who met the American College of Rheumatology (ACR) criteria for giant cell arteritis or Takayasu's arteritis (TA) on retrospective review. A positive FDG-PET for large vessel inflammation assisted the primary clinician in making the diagnosis of unclassified large vessel vasculitis in six patients. Four of the seven patients who had more than one scan for large vessel vasculitis demonstrated normalized FDG uptake on subsequent scans after a period on glucocorticoid treatment. The remaining three patients persisted in having increased FDG uptake on FDG-PET imaging while on active treatment. Conclusion Fluorine-18-labelled deoxyglucose positron emission tomography has a role in the diagnosis of large vessel vasculitis, particularly in patients with a high suspicion of active large vessel vasculitis who do not meet the ACR criteria. FDG-PET may have a role in monitoring disease activity in selected patients with large vessel vasculitis especially in identifying occult sites of large vessel inflammation or to titrate prednisolone therapy.