Do Monosodium Urate Crystals Reduce at Different Rates in Joints and Tendons During Urate-Lowering Therapy? A Dual-Energy Computed Tomography Study

Objective Prior imaging studies have suggested that monosodium urate (MSU) crystal deposits in joints dissolve more rapidly than those in tendons during urate-lowering therapy (ULT) for gout. This study aimed to examine whether urate deposits visible on dual-energy computed tomography (DECT) reduce at different rates in joints and tendons during ULT.

Methods Participants with gout from 2 clinical trials of oral ULT with the following criteria were included: paired DECT scans of the feet and ankles over 1-year of ULT, first DECT scan showing total urate volume ≥ 0.5 cm³, second DECT scan showing reduced total urate volume, and DECT deposition visible in at least 1 joint and 1 tendon on the first scan. DECT urate volumes in up to 3 index joints and up to 3 index tendons at baseline and year 1 were measured in known order. Data were analyzed using a general linear mixed analysis of covariance.

Results In total, 125 joint deposits and 95 tendon deposits were analyzed from 50 participants. The least means change (95% CI) in DECT urate volumes of the joint deposits was −0.37 (−0.47 to −0.26) cm³ and of the tendon deposits was −0.39 (−0.50 to −0.27) cm³ (both P < 0.001). There was no difference in the change in DECT urate volumes between the joint and tendon deposits; least means difference was 0.02 (95% CI −0.09 to 0.13) cm³ (P = 0.73).

Conclusion This DECT study indicates that similar rates of MSU crystal dissolution occur at both joints and tendons during oral ULT.