Background/Purpose: Provisional domains and definitions for gout remission criteria have been proposed using consensus methodology (de Lautour et al, Arthritis Care Res 2016). These criteria include 5 domains: serum urate, tophus, flares, pain due to gout, and patient global assessment (Table). Dual energy CT (DECT) is an advanced imaging technique that allows color coding and volumetric measurement of urate crystal deposition. The aim of this study was to test the construct validity of the provisional remission criteria by examining the association of each domain and the full remission criteria with DECT urate crystal deposition.

Methods: Patients with gout on allopurinol ≥300 mg daily for at least 3 months were prospectively recruited into a multicenter DECT study, using monitored enrollment to include approximately 25% of patients with subcutaneous tophi and 50% with serum urate <6.0mg/dL. Participants all fulfilled the 1977 ARA gout classification criteria, and attended a standardized study visit, which recorded gout flare frequency in the preceding 12 months, physical examination for tophus, serum urate, and patient questionnaires. DECT of both hands/wrists, feet/ankles/Achilles, and knees were performed using the second-generation Siemens 128-slice Definition Dual Source scanner, and urate crystal volume was measured by 2 DECT radiologists. The relationship between the DECT urate crystal volume and deposition with each domain as well as with the full remission criteria set (all 5 domains achieved) was analyzed.

Results: With the exception of the pain domain, participants fulfilling each remission domain had lower DECT urate crystal volume than those who did not fulfil the domain (Table). All 5 remission domains were achieved in 23/152 (15.1%) participants. Of those fulfilling the provisional remission criteria, 10/23 (43.5%) had DECT urate crystal deposition, compared with 95/129 (73.6%) of those not fulfilling the remission criteria (P<0.001). The median (range) DECT urate crystal volume was 0.00 (0.00-0.46) cm³ for those fulfilling the remission criteria, compared with 0.08 (0.00-19.53) cm³ for those not fulfilling the criteria (P=0.002). In multivariate linear regression (of ranked DECT crystal volume data) and logistic regression models including all 5 remission domains, the serum urate and tophus domains were independently associated with the DECT urate crystal volume and deposition.

Conclusion: In people with gout taking allopurinol, a state of remission defined by the provisional remission criteria is associated with lower DECT urate crystal deposition. Furthermore, those domains most directly related to monosodium urate crystal pathophysiology (serum urate and tophus) are independently associated with urate crystal deposition measured by DECT. Overall, these findings support the construct validity of the provisional gout remission criteria.