OP0287 LONGITUDINAL ASSESSMENT OF THE ULTRASOUND GOUT LESIONS USING THE VALIDATED OMERACT SEMI-QUANTITATIVE SCORING SYSTEM

Abstract

BackgroundIn gout, ultrasound (US) is a promising tool to detect changes in monosodium urate (MSU) depositions during urate-lowering therapy (ULT). The OMERACT US group has developed definitions of gout-specific US lesions[1] and a semi-quantitative scoring system for US lesions representing MSU deposition (tophus, double contour (DC) and aggregates)[2], but the responsiveness of lesions when applying this scoring system has not yet been assessed.ObjectivesThe primary aim was to evaluate the responsiveness of gout-specific US lesions in patients receiving treat-to-target ULT using both a binary (present/absent) and the OMERACT-defined semi-quantitative (0-3) scoring system. The secondary aims were to determine the most responsive US measure for MSU deposition at patient level and the optimal joint/tendon set for monitoring lesions.MethodsUS (28 joints, 14 tendons) was performed in microscopically verified gout patients initiating/increasing ULT and repeated after 6 and 12 months. Static images and videos of pathologies were stored. Tophus, DC and aggregates were scored binarily and semi-quantitatively. Individual lesion-scores were calculated at patient level as were combined crystal sum scores. Standardised response means (SRM) for lesions when scored binarily and semi-quantitatively were calculated at patient and joint/tendon level.ResultsSixty-three patients were followed for 12 months. Plasma urate levels were effectively lowered during follow-up (Table 1). US showed statistically significant decreases in tophus and DC sum scores, both when scored binarily and semi-quantitatively, whereas aggregates were almost unchanged during follow-up (Table 1). SRMs for the semi-quantitative tophus and DC sum scores were markedly higher than those for the binary. The most responsive measure for urate deposition at patient level was a combined semi-quantitative tophus-DC-sum score (SRM 0.92, Table 1). A reduced joint/tendon set for monitoring included knee and 1st–2nd metatarsophalangeal joints and peroneus and distal patella tendons representing the most prevalent and responsive sites (SRM 1.13, Figure 1).Table 1.Course and SRMs of US scores during 12 months’ follow-upBaseline6-months’ follow-up12-months’ follow-upP-value*SRMMeanMedian [IQR]MeanMedian [IQR]MeanMedian [IQR]Δ 0–6 monthsΔ 6–12 monthsΔ 0–12 months12 monthsP-urate (mmol/L)0.490.48 [0.42;0.56]0.330.32 [0.29; 0.36]0.310.30 [0.27;0.35]<0.0010.0464<0.001-SQ ultrasound scoring (0–3), [possible range]:DC sum score, [0–84]5.53 [1; 8]3.72 [0; 5]2.21 [0; 4]<0.001<0.001<0.0010.80Tophus sum score, [0–126]9.56 [4; 11]8.25 [3; 9]6.44 [2; 7]<0.001<0.001<0.0010.84Aggregates sum score, [0–126]12.210 [7; 16]12.610 [7; 16]11.811 [6; 15]0.8750.1920.5820.07SQ-TD-sum score, [0–210]15.010 [6; 16]11.98 [5; 12]8.76 [4; 9]<0.001<0.001<0.0010.92SQ-TDA-sum score, [0–336]27.222 [14; 30]24.618 [12; 28]20.516 [9; 25]<0.001<0.001<0.0010.73Binary ultrasound scoring (0–1), [possible range]:DC sum score, [0–28]1.81 [0; 3]1.11 [0; 2]0.60 [0; 1]<0.001<0.001<0.0010.72Tophus sum score, [0–42]3.42 [1; 4]3.02 [1; 3]2.32 [0; 3]0.002<0.001<0.0010.75Aggregates sum score, [0–42]4.43 [2; 6]4.74 [2; 6]4.24 [2; 6]0.3560.1250.7320.07Binary-TD-sum score, [0–70]5.33 [2; 6]4.23 [1; 4]2.92 [1; 3]<0.001<0.001<0.0010.86Binary-TDA-sum score, [0–112]9.78 [5; 11]8.87 [4; 10]7.16 [3; 9]<0.0010.001<0.0010.70US, ultrasound; SQ, semi-quantitative; SRM, standardised response mean; DC, double contour; TD-sum score, tophus+DC sum score, TDA-sum score, tophus+DC+aggregates sum score. * Wilcoxon signed rank test, statistically significant results are indicated by bold-face type.ConclusionThe OMERACT consensus-based semi-quantitative US gout scoring system showed longitudinal validity with both tophus and DC being highly responsive to treatment. A responsive US measure for urate deposition and a feasible joint/tendon set for monitoring are proposed.