Imaging as a potential outcome measure in gout studies: A systematic literature review.

OBJECTIVE: Despite major progress in the imaging of gout, it is unclear which domains these techniques can evaluate and whether imaging modalities have the potential to provide valid outcome measures. The aim of this study was to assess the use of imaging instruments in gout according to the Outcomes in Rheumatology Clinical Trials (OMERACT) filter to inform the development of imaging as an outcome measure.

METHODS: A systematic literature search of imaging modalities for gout was undertaken. Articles were assessed by two reviewers to identify imaging domains and summarize information according to the OMERACT filter.

RESULTS: The search identified 78 articles (one abstract). Modalities included were conventional radiography (CR) (16 articles), ultrasound (US) (29), conventional computed tomography (CT) (11), dual energy computed tomography (DECT) (20), and magnetic resonance imaging (MRI) (16). Three domains were identified as follows: urate deposition, joint damage, and inflammation. Although sufficient data were available to assess feasibility, validity, and reliability, comprehensive assessment of discrimination was not possible due to the paucity of prospective imaging studies. CR is widely accessible, inexpensive with a validated damage scoring system. US and MRI offer radiation-free methods of evaluating urate deposition, damage and inflammation, but may be limited by accessibility. DECT provides excellent definition of urate deposition and bone damage, but has restricted availability and requires radiation.

CONCLUSIONS: Imaging methods can detect urate deposition, damage, and inflammation in gout. More than one modality may be required depending on the domains and therapeutic agent of interest. No single imaging method currently fulfils all aspects of the OMERACT filter for any domain.