Adding ultrasound (US) to the clinical exam helps predict the likelihood of future gout flares, results of a prospective, observational study conducted in Italy suggest.
“Baseline US findings indicative of MSU [monosodium urate] burden and US-detected inflammation are independent predictors of gout flares over 12 months,” lead author Edoardo Cipolletta, MD, of the rheumatology unit, department of clinical and molecular sciences at Marche Polytechnic University in Ancona, Italy, and colleagues wrote in Rheumatology.
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“We demonstrated that US findings provided an additional value over clinical data in estimating the risk of flares. Moreover, we reported an association between US findings at a joint and the occurrence of gout flares at the same joint,” they added.
Predicting risk of flares and reducing their occurrence are two main challenges in managing gout, the authors wrote. US can be used to scan multiple joints and is widely used in Europe as a low-cost, radiation-free imaging tool that’s easily integrated into clinical practice.
To investigate whether US can predict gout flares, the researchers enrolled 81 consecutive adult patients with gout in the study between April 2019 and March 2021 at one academic rheumatology treatment site in Italy and followed them for 12 months. The authors compared cases (who developed at least one flare within 12 months of the baseline visit) with controls (who self-reported no gout flares over that period).
Patients diagnosed with other inflammatory arthritis and those with coexisting calcium pyrophosphate deposition disease were excluded from the study.
The 71 participants who completed the study were, on average, in their early 60s, and in both groups, all but one were male. At the baseline visit, all had been on stable urate-lowering therapy for at least 6 months and had not had any gout flares in 4 weeks. The mean gout duration was 7 years in the case group and 8 years in controls.
At baseline, all participants underwent physical examination and US of elbows, wrists, second metacarpophalangeal joints, knees, ankles, and first metatarsophalangeal joints by a member of the research team who was blinded to the clinical and laboratory data.
Clinical assessments were scheduled at baseline and at 6-month intervals, and all participants were evaluated by a second researcher who was blinded to US findings.
During follow-up visits, participants were asked to report any gout flare, considered to meet at least three of four criteria: patient-defined flare, pain at rest score higher than 3 on a 0-10 scale, at least one swollen joint, and at least one warm joint. Patients not reaching their target serum urate goal received escalated urate-lowering therapy dosage and anti-inflammatory prophylaxis.
The US indicators of MSU deposits – aggregates, double contour sign, and tophi – were recorded as present or absent. The power Doppler signal was scored from 0 through 4, and summated scores for each US finding were calculated.
Over 12 months, the researchers found:
- Thirty (42.3%) patients had at least one flare, with a median of 2.0 flares. Patients with flares had higher a US median total MSU score (5.0 vs. 2.0; P = .01) and power Doppler signal (3.0 vs. 0; P < .01) than controls.
- In multivariate analysis, baseline US scores indicating MSU deposits and US-detected inflammation were significantly linked with the occurrence of flares. The adjusted odds ratio for total MSU score was 1.75 (95% confidence interval, 1.26-2.43) and for power Doppler score was 1.63 (95% CI, 1.12-2.40).
- Also in a multivariate analysis, baseline US scores indicating MSU deposits and US-detected inflammation were significantly linked with the number of flares. The incidence risk ratio for total MSU score adjusted was 1.17 (95% CI, 1.08-1.26) and for power Doppler score was 1.29 (95% CI, 1.19-1.40).