Objectives: To evaluate whether ultrasound (US) findings indicating monosodium urate (MSU) deposits and US-detected inflammation [i.e. power Doppler (PD) signal] predict gout flares over 12 months.
Methods: Gout patients on urate-lowering therapy for at least the preceding six months were enrolled consecutively in this 12-month prospective, observational, single-centre study. A nested case-control analysis was performed. Cases were participants with at least one flare in the follow-up period, while controls did not self-report any gout flare. The US assessment included elbows, wrists, 2nd metacarpophalangeal joints, knees, ankles, and 1st metatarsophalangeal joints. The US findings indicating MSU deposits [i.e. aggregates, double contour (DC) sign and tophi] were identified as present/absent according to the Outcome Measure in Rheumatology definitions. PD signal was scored semi quantitatively. Summated scores were calculated for each US finding.
Results: Eighty-one gout participants were enrolled, and 71 completed the study. Thirty (42.3%) of 71 participants experienced at least one flare over 12 months, with a median of 2.0 flares. Cases had a greater US burden of MSU deposits (6.7 ± 4.7 vs 2.9 ± 2.6, p= 0.01) and PD signal (3.73 ± 3.53 vs 0.82 ± 1.44, p< 0.01) than controls, at baseline. The baseline US scores indicating MSU deposits and US-detected inflammation were significantly associated with the occurrence [total MSU score, adjusted Odds Ratio (aOR):1.75, 95%CI : 1.26-2.43; PD score, aOR : 1.63, 95%CI : 1.12-2.40] and the number (total MSU score, aIRR : 1.17, 95%CI : 1.08-1.26; PD score, aIRR : 1.29, 95%CI : 1.19-1.40) of flares over 12 months in multivariate analyses.
Conclusions: Baseline US findings indicating MSU deposits and US-detected inflammation are independent predictors of gout flares over 12 months.
Keywords: “Double contour” sign; Gout; Gout flares; Monosodium urate; Power Doppler; Tophus; Ultrasound.