OP0050 ADDITIVE VALUE AND DIAGNOSTIC ACCURACY OF DUAL-ENERGY CT FOR THE DIAGNOSIS OF GOUT: A PROSPECTIVE STUDY IN SUBJECTS WITH UNCLASSIFIED MONO OR OLIGOARTHRITIS

Background: The latest diagnostic technique to visualize monosodium uric acid (MSU) depositions is Dual Energy CT scan (DECT).1 Objectives: To assess the additive value and accuracy of DECT in diagnosing gout in a prospective study in subjects with unclassified arthritis. Methods: We included 100 consecutive patients with acute unclassified mono or oligo arthritis who presented to the outpatient clinic of the Department of Rheumatology of Meander Medical Centre, Amersfoort, the Netherlands, ClinicalTrials.gov NCT03038386. Eleven patients dropped out, see Figure. Patients underwent aspiration of the arthritic joint (see Table) and a DECT scan of hands and wrists, knees, ankles and feet bilaterally. The 2015 EULAR/ACR gout classification criteria were used to score the subjects, with and without DECT result, to determine the additive value of DECT. Sensitivity and specificity of DECT for diagnosing gout were calculated separately for at the joint and at individual persons’ level, using as reference standards microscopy of synovial fluid (SF) and the gout classification criteria. Results: For demographic and clinical characteristics of the patients see Table 1, and for study data and outcomes see Figure and Table 2. Sixty-eight of 89 patients (76.4%) fulfilled the 2015 EULAR/ACR criteria for gout. Of the 98 patients with SF aspiration, 55 (56%) were positive for MSU; of these, 89 subjects underwent DECT, of whom 38 had a negative microscopy result. Of these 38 subjects, 14 (37%) met the gout classification criteria only after a positive DECT result. Conclusion: Our findings suggested that DECT could have an additive value to clinical algorithms in subjects with undifferentiated arthritis when microscopy of SF fails to demonstrate the presence of MSU crystals. References: [1] Choi HK, et al. Dual energy CT in gout: a prospectieve validation study. Ann Rheum Dis2012; 71:1466-71. Disclosure of Interests: Mihaela Gamala: None declared, Johannes W. G. Jacobs Grant/research support from: Roche, Consultant for: Roche, Suzanne Linn-Rasker: None declared, Maarten Nix: None declared, Ben Heggelman: None declared, Pieternel Pasker: None declared, Jacob M. van Laar Grant/research support from: Genentech, Consultant for: F. Hoffmann-La Roche, Ruth Klaasen: None declared