Compared with normouricemic individuals, patients with asymptomatic hyperuricemia had ultrasound images with a high prevalence of tophus at the first metatarsophalangeal (MTP) joint and the double contour sign at the first MTP joint and femoral condyle, according to findings published in Seminars in Arthritis and Rheumatism.
Although ultrasound sometimes shows gout-related lesions in asymptomatic hyperuricemia, the most common characteristic signs and their related anatomic sites have yet to be defined. In a first of its kind review, investigators sought to examine the prevalence of these typical gouty ultrasound lesions, as defined by the Outcome Measures in Rheumatology (OMERACT) initiative, in asymptomatic hyperuricemia, and to determine their ability to differentiate from normouricemia.
A systematic literature review and meta-analysis was conducted in July 2018, searching databases including Ovid Medline, PubMed, Embase, and the Cochrane Library for relevant articles that involved asymptomatic hyperuricemia and reported the prevalence of at least 1 of 4 OMERACT elementary ultrasound lesions, including double contour sign, tophus, erosion, or hyperechoic aggregates. Pooled prevalence and pooled odds ratios (OR) for discrimination from normouricemia were calculated.
There were 20 studies reviewed and included in the qualitative analysis, 11 of which were also used for quantitative meta-analysis. Pooled sample sizes were 812 with asymptomatic hyperuricemia, 505 with normouricemia, and 778 with gout, with 7.0 mg/dL used as the most common cutoff between the first 2 categories. The first MTP joint was the most frequently scanned site (n=17 studies), and double contour sign, tophus, erosion, and aggregates were included in 18, 16, 9, and 6 articles, respectively.
In patients with asymptomatic hyperuricemia, limb-based pooled prevalence revealed that the double contour sign at the first MTP joint was the most frequent ultrasound finding (OR, 0.31; 95% CI, 0.20-0.42), and the first MTP joint tophus (OR, 0.16; 95% CI, 0.03-0.29) and femoral condyle double contour sign (OR, 0.16; 95% CI, 0.08-0.24) were the next most common lesions observed. Person-based pooled prevalence showed the first MTP joint double contour sign (OR, 0.45; 95% CI, 0.22-0.68) and the first MTP joint tophus (OR, 0.21; 95% CI, -0.03 to 0.45) were most common.
When comparing normouricemia and asymptomatic hyperuricemia, limb-based pooled ORs for the latter were 13.67 (95% CI, 5.42-34.49) for the femoral condyle double contour sign, 6.98 (95% CI, 3.14-15.57) for the first MTP joint double contour sign, and 6.10 (95% CI, 1.55-24.04) for the first MTP joint tophus. The double contour sign (OR, 13.68; 95% CI, 2.47-75.72) and tophus (OR, 5.06; 95% CI, 0.98-26.18) were best able to discriminate between the 2 groups in terms of person-based pooled ORs.
As expected, when comparing gout and asymptomatic hyperuricemia, gout had significantly higher pooled ORs for the first MTP joint tophus in both limb-based (OR, 3.69; 95% CI, 1.90-7.16) and person-based (OR, 6.66; 95% CI 2.06-21.56) analyses.
Study limitations included ultrasound heterogeneity, inconsistency in definitions, low methodologic quality, clinical or demographic heterogeneity, reporting inconsistencies, lack of aggregate prevalence estimates, possible underestimation of lesion prevalence at uncommon sites, use of only OMERACT definitions, and lack of effusion and synovitis assessment.
“These findings have the potential to inform further research which evaluates the significance of subclinical [monosodium urate] crystal deposition in the transition from [asymptomatic hyperuricemia] to symptomatic gout,” noted the authors. They recommended that future research involve longitudinal studies that explore the optimal joint combination for scanning.
Stewart S, Maxwell H, Dalbeth N. Prevalence and discrimination of OMERACT-defined elementary ultrasound lesions of gout in people with asymptomatic hyperuricaemia: A systematic review and meta-analysis [published online January 11, 2019]. Semin Arthritis Rheum. doi:10.1016/j.semarthrit.2019.01.004