POS0139 TWO-YEAR REDUCTION OF URATE LOAD IN DUAL-ENERGY CT DURING A TREAT-TO-TARGET APPROACH IN GOUT PATIENTS: RESULTS FROM A LONGITUDINAL STUDY (NOR-GOUT)
Authors: T. Uhlig, T. Eskild, L. F. Karoliussen, T. K. Kvien, E. A. Haavardsholm, N. Dalbeth, H. B. Hammer
Journal: Annals of the Rheumatic Diseases (2021)

Background: Dual-energy computed tomography (DECT) detects urate depositions, and is included in the ACR/EULAR classification criteria for gout. There is lack of longitudinal studies in large patient populations for changes in urate deposition measured by DECT during urate lowering therapy (ULT). Objectives: To explore by DECT the longitudinal changes urate depositions during a treat-to-target approach in gout with ULT. Methods: In a prospective observational study, patients with crystal-proven gout were included if they presented after a recent gout flare and with increased serum urate levels (&gt;360 μmol/L/&gt;6 mg/dl). In a treat-to-target approach they received ULT with escalating drug doses with monthly follow-up during the first year until the treatment target was met with serum urate &lt;360 μmol/L or 360 µmol/L if tophi. A DECT scanner (General Electric Discovery CT750 HD) acquired data from bilateral forefeet and ankles at 80 KW and 140 KV, processed with a software with a 2-material decomposition algorithm which colour codes urate. Follow-up DECT was performed after one and two years. Images were scored with a semiquantitative method (Bayat et al. 2015) by one experienced radiologist in known order and blinded to serum urate and clinical data. Each scan assessed four regions: the first metatarsophalangeal (MTP1) joint, the other joints of the toes, the ankles and midfeet, and all visible tendons in the feet and ankles. Each region was then scored according to the maximum amount of urate deposition observed on visual inspection (0=no deposits, 1=dots, 2=single deposit, 3=more than one deposit). A total DECT sum score was derived by adding all values from the four regions, with a maximum score of 12. Results: DECT was at baseline measured in 187 of 211 patients. 95.2% were males, mean (SD) age was 56.7 (13.7) years, disease duration 8.1 (7.9) years), and 17% had clinical tophi. The total DECT scores and all subscores decreased from baseline to 2 years (p&lt;0.001 for all comparisons versus baseline), table 1. The mean (SD) serum urate level (μmol/L) decreased from 501 (80) at baseline to 311 (48) at 12 months and 322 (67) at 24 months. Reaching the treatment target &lt;360 µmol/L after year 1 or 2 was only numerically but not statistically related to reductions in DECT scores. Patients with clinical tophi at baseline had larger reductions in total DECT scores after 1 (3.4 vs. 1.5, p&lt;0.01) and 2 years (6.5 vs. 2.3, p&lt;0.001) than patients without tophi. Conclusion: During a treat-to-target approach urate deposition visualised by DECT were clearly reduced in ankles and feet after 1 year with further reduction after 2 years. Table 1. Baseline (n=187) Mean (SD) 1 year (n=157) Mean (SD) 2 years (n=166) Mean (SD) MTP1 (0-3) 1.4 (2.0) 1.0 (1.7) 0.6 (1.3) Toes (0-3) 1.0 (1.8) 0.6 (1.4) 0.3 (1.0) Ankle/Midfoot (0-3) 1.2 (2.1) 0.7 (1.6 0.3 (1.0) Tendons (0-3) 1.0 (1.7) 0.5 (1.2) 0.3 (0.8) Sum score (0-12) 4.6 (6.4) 2.8 (4.7) 1.5 (3.2) Disclosure of Interests: Till Uhlig Speakers bureau: Grünenthal, Novartis, Consultant of: Grünenthal, Novartis, Tron Eskild: None declared, Lars Fridtjof Karoliussen: None declared, Tore K. Kvien Consultant of: AbbVie, MSD, UCB, Hospira/Pfizer, Eli-Lilly, Roche, Hikma, Orion, Sanofi, Celltrion, Sandoz, Biogen, Amgen, Egis, Ewopharma, Mylan, Grant/research support from: BMS, AbbVie, MSD, UCB, Hospira/Pfizer, Eli-Lilly, Espen A Haavardsholm Consultant of: Pfizer, UCB, Eli Lilly, Celgene, Janssen-Cilag, AbbVie and Gilead, Nicola Dalbeth Speakers bureau: Menarini, AstraZeneca, Takeda, S. Nicolaou, Consultant of: AstraZeneca, Fonterra, Takeda, Pfizer, Cymabay, Crealta, Grant/research support from: AstraZeneca, Siemens Healthcare, Hilde Berner Hammer Consultant of: AbbVie, Lilly and Novartis