Background:Classification criteria are used for classifying groups of patients, especially for clinical trials, and diagnostic criteria for diagnosis in individual patients.Objectives:to establish the performance of the 2015 ACR/EULAR gout classification criteria for the diagnosis gout in patients with undifferentiated arthritis. Secondary, to explore the use and efficacy of uric acid lowering therapy (ULT) in daily clinical practice in new gout patients.Methods:1-year follow-up study was performed in subjects with unclassified arthritis, who had been classified as gout patients or not, according the gout classification criteria, including imaging with dual-energy CT, but without ultrasonography and joint X-rays.(1) The reference was the clinical diagnosis (gout yes/no) after 1-year follow-up.Results:71 patients were included; their demographic and clinical characteristics are summarized in Table 1. All 63/71 patients classified as having gout at baseline also had a clinical gout diagnosis after one year, and of the patients not classified, none had the clinical diagnosis of gout at one year.Table 1.Characteristics of the 71subjects included in analysesDiagnosis**gout (n=63)no gout (n=8)Age in years, mean (SD)62 (14)59 (14)Male gender, N (%)53 (84)5 (63)Symptom duration* at baseline in months, median (IQR)12 (1-48)8 (0.5-33)Joint involvement at baseline N patients (%):MTP,33 (52)1 (12)ankle/midfoot12 (19)1 (12)other joint18 (29)6 (76)SUA intercritical in umol/l, mean (SD)484 (63)337 (71)2015 ACR/EULAR criteria baseline score, mean (SD)***10.3 (2.5)2.6 (1.5)2015 ACR/EULAR criteria ≥8 points, N patients (%)***57 (90)0 (0)MSU crystal positive joint aspiration, N patients (%)44 (70)0 (0)DECT positive, N patients (%)49 (78)0 (0)* self-reported, intermittent symptoms; ** all patients classified with gout at baseline also had a clinical gout diagnosis after one yea; *** using a somewhat limited set, see methodsMTP, metatarsophalangeal joints; SUA, serum uric acid; DECT, dual-energy CT; MSU, monosodium urate;.Sensitivity, specificity, positive and negative predictive value, and accuracy values (95% CI) of the classification criteria set we used were 0.91 (0.80-0.96); 1 (0.63-1); 1; 0.57 (0.38-0.74) and 0.92 (0.83-0.97), respectively. The area under the receiver operating characteristics curve (95% CI) was 0.95 (0.91-0.99).ULT was started in 49/63 (78%) of gout patients; 45/49 (92%) of them had serum uric acid levels ≤ 360 μmol/l and no recurrent gout attack during one-year follow-up.Conclusion:The 2015 ACR-EULAR gout classification criteria performed well for the diagnosis gout in clinical practice. Most gout patients had been treated successfully, according to current guidelines.References:[1]Gamala M, Jacobs JWG, Linn-Rasker SF, Nix M, Heggelman BGF, Pasker-de Jong PCM, et al. The performance of dual-energy CT in the classification criteria of gout: a prospective study in subjects with unclassified arthritis. Rheumatology 2019 Sep (Epub ahead print).Disclosure of Interests:Mihaela Gamala: None declared, Johannes W. G. Jacobs Grant/research support from: 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: MSD, Genentech, Consultant of: MSD, Roche, Pfizer, Eli Lilly, BMS, Ruth Klaasen: None declared
In vivo identification of uric acid stones with dual-energy CT: diagnostic performance evaluation in patients