Dalbeth, NicolaNicolaou, SavvasBaumgartner, ScottHu, JiaFung, MapleChoi, Hyon2018-04-192018Dalbeth, Nicola, Savvas Nicolaou, Scott Baumgartner, Jia Hu, Maple Fung, and Hyon K Choi. 2018. “Presence of monosodium urate crystal deposition by dual-energy CT in patients with gout treated with allopurinol.” Annals of the Rheumatic Diseases 77 (3): 364-370. doi:10.1136/annrheumdis-2017-212046. http://dx.doi.org/10.1136/annrheumdis-2017-212046.http://nrs.harvard.edu/urn-3:HUL.InstRepos:35981880Objective: Dual-energy CT (DECT) detects and quantifies monosodium urate (MSU) crystal deposition with high precision. This DECT study assessed crystal deposition in patients with gout treated with stable-dose allopurinol, and investigated potential clinical determinants for crystal deposition. Methods: Patients with gout treated with allopurinol ≥300 mg daily for at least 3 months were prospectively recruited from the USA and New Zealand, using monitored enrolment to include approximately 25% patients with palpable tophi and approximately 50% with serum urate (sUA) levels <6.0 mg/dL (<357µmol/L). MSU crystal deposition was measured in the hands/wrists, feet/ankles/Achilles and knees bilaterally. The presence and total volume of crystals were assessed by DECT and analysed according to sUA levels and gout characteristics. Results: Among 152 patients receiving allopurinol ≥300 mg/day for 5.1 years on average, 69.1% had crystal deposition on DECT, with a median total crystal volume of 0.16 cm3 (range: 0.01–19.53 cm3). The prevalence of crystal deposition ranged from 46.9% among patients with sUA <6.0 mg/dL and no palpable tophi to 90.0% among those with sUA ≥6.0 mg/dL and tophi. Total volume of crystal deposition was positively associated with sUA ≥6.0 mg/dL, gout flares within the past 3 months and tophi. Total volume of crystal deposition correlated positively with Patient Global Impression of Disease Activity scores. Conclusion: A substantial proportion of patients without palpable tophi have MSU crystal deposition, despite receiving allopurinol doses ≥300 mg/day for a considerable duration. Patients with higher sUA and clinical features of severe disease have a higher frequency and greater volume of MSU crystal deposition.en-USgouttreatmentpatient perspectiveJournal Article2018-04-1910.1136/annrheumdis-2017-212046