Background/Purpose:

 Uric monosodium urate (MSU) depositions are detected by ultrasound (US), and US is included in the ACR/EULAR classification criteria for gout. OMERACT definitions for US elementary lesions in gout include the double contour sign (DC) (deposits of crystals on the surface of cartilage), tophus (larger hypo-echoic aggregation of crystals, usually well delineated), aggregates (small hyper-echoic deposits) and erosions. MSU depositions have some predilection sites, but only a few small studies have explored the decrease of depositions during treatment. The present purpose was to explore by US the longitudinal development of MSU depositions during a treat-to-target approach with urate lowering therapy (ULT) in patients with gout.

Methods:

In a prospective observational study, patients with crystal-proven gout were included after a recent gout flare and if increased serum urate levels (>360 μmol/L/>6 mg/dl). In a treat-to-target approach using ULT and increasing drug doses with monthly follow-up until treatment target was met (<360 μmol/L, or <300 μmol/L if clinical tophi). An extensive US assessment was performed (GE E9 machine, grey scale 15MHz) at baseline and after 3, 6 and 12 months to detect MSU depositions (DC, tophi and aggregates) with bilateral assessment of radiocarpal joint, MCP 2, insertion of triceps and quadriceps, proximal and distal patellar and the Achilles tendon, cartilage of distal femur (maximal flexed knee) and the talar cartilage and MTP 1 joint. The degree of elementary lesions was semi quantitatively scored 0-3 (0=none, 1=possible, 2=certain, 3=major deposits). Total sum scores of DC, tophi and aggregates separately as well as all lesions were calculated for each visit. Changes from baseline were explored by paired samples T-test.

Results:

161 patients were included at baseline (93.3% men, mean (SD) age 57.0 (14.1) years, disease duration 8.0 (7.7) years). The mean (SD) serum urate level decreased from 487 (82) μmol/L at baseline to 312 (52) μmol/L at 12 months (p<0.001). Sum scores of deposits decreased over 12 months (table, *=p<0.05, **=p<0.001), and the numeric decrease was largest for DC (figure). In addition, the percentage of patients with no detected lesion increased most for DC (baseline to 12 months; DC: 8 to 53%, tophi: 8 to 16% and aggregates 1 to 3%).

Conclusion:

During a treat-to-target approach with ULT all forms of deposits decreased, and most extensively for DC. This study shows that reduction of the uric load in gout during treat-to-target ULT may be visualised by US, and that DC may be the lesion most sensitive to change.