Background/Purpose: To evaluate the sensitivity to change of ultrasound (US) structural gout lesions, as defined by the OMERACT US group, in gout patients during urate lowering therapy.

Methods: US examination (28 joints, 26 tendons) was performed in patients with microscopically verified gout, who initiated or increased urate lowering therapy. Joints and tendons were evaluated by US for the OMERACT structural gout lesions (double contour sign (DC), tophus, aggregates and erosions), scored binarily (0/1). Synovial changes were graded by grey scale (GS) and color Doppler (CD), both scored semiquantitatively (0-3), where a score > 1 was considered pathological. A sum score was calculated for each lesion for each patient. Numbers of gout attacks within the last 4 and 12 weeks and Patient Reported Outcomes (PROs) regarding pain (visual analogue scale (VAS)) and physical function (HAQ) were obtained, as were CRP, p-urate and clinical joint examination. All examinations were repeated after 3 and 6 months. Changes in patient’s sum scores and lesion scores at different locations (joints and tendons) were evaluated using Wilcoxon-Pratt signed-rank test. Furthermore, changes in lesion scores between groups that did/did not achieve the treatment target (p-urate < 0.36 mmol/L) were compared using Mann Whitney U test and Chi square test.

Results: 50 patients (48 males, 2 females), mean age of 68.9 years (range 30-88) were included. US showed a statistically significant decrease in DC and tophus sum scores from both 0-3 and 3-6 months (table 1). The aggregate sum score only showed a statistically significant decrease from 3-6 months, whereas the erosion sum score was almost unchanged in the follow-up period. GS and CD synovitis sum scores both showed statistically significant decreases at 6 months’ follow up, and for CD also from 0-3 months (table 1).

Structural lesions were most commonly found in metatarsophalangeal 1-4 and knee joints, which were also the locations with the most pronounced changes in scores (figure 1).

Tender and swollen joint counts, PROs and number of joint attacks declined statistically significantly from 0-3 months, except for the HAQ, which only declined numerically. P-urate levels decreased statistically significantly from both 0-3 months and 3-6 months (table 1).

No statistically significant differences in US sum score changes during follow up were observed between groups that did/did not obtain the treatment goal.

Conclusion: Of the four US structural gout lesions, DC and tophus showed sensitivity to change after only 3 months of urate lowering therapy, using a binary score, whereas aggregates only showed a change after 6 months follow-up.

This study indicates that US assessment of the OMERACT structural gout lesions, particularly DC and tophus, seems to be a useful tool for monitoring improvement over time. Future studies should investigate whether more sensitive monitoring may be obtained by using a semiquantitative scoring system.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/assessing-the-sensitivity-to-change-of-the-omeract-ultrasound-structural-gout-lesions-during-urate-lowering-therapy/