Background: Musculoskeletal ultrasound allows visualization of monosodium urate (MSU) crystal deposition in people with gout, most commonly as double contour signs, tophi, and aggregates. Prior ultrasound studies have reported that these ultrasound findings may be present in people with asymptomatic hyperuricemia; 14% to 59% of people with apparently asymptomatic hyperuricemia have ultrasound evidence of MSU crystal deposition. The Outcomes in Rheumatology (OMERACT) ultrasound working group has developed definitions for ultrasound elementary gout lesions, together with a semi-quantitative ultrasound scoring system for gout [1].

Objectives: To describe the musculoskeletal ultrasound features of asymptomatic hyperuricaemia using the OMERACT gout semi-quantitative scoring system and examine relationships between ultrasound lesions.

Methods: Baseline visit data from the T ransitions in G out R e sea r ch (TIGER) study, a multi-national prospective cohort study of people with asymptomatic hyperuricemia, were analysed. Participants with serum urate ≥0.48mmol/L, no previous gout flares, and no subcutaneous tophi (n=269) underwent a standardized ultrasound examination of both patellar ligaments, knees, 1st and 2nd metatarsophalangeal joints (MTP) and Achilles tendons. Double contour and tophus were scored at the time of scanning according to the OMERACT gout ultrasound semi-quantitative scoring system (0-3, with score >1 indicating a definite finding), together with aggregates, erosion, synovial hypertrophy and power Doppler activity. For elementary ultrasound lesions, semi-quantitative sum scores for each ultrasound lesion and the proportion of participants with at least one definite ultrasound lesion were calculated. A combined semi-quantitative double contour-tophus (SQDT) sum score was calculated by summing the double contour and tophus scores for all scanned sites, with a maximum score of 60. Bivariate Spearman correlation analyses were performed. The odds of an ultrasound score >1 at each joint were modelled with a binomial distribution and a logit link function.

Results: The mean (SD) age was 48 (18) years and 81% were male. The mean (SD) serum urate at screening was 0.52 (0.04) mmol/L. For the ultrasound elementary gout lesions, scores >0 were common, particularly for double contour (Table 1). There were 77 (28.6%) participants with at least one definite (score >1) double contour, 46 (17.1%) with at least one definite tophus, and 104 (38.7%) participants with at least one definite double contour and/or tophus. Definite aggregates were present in 50 (18.6%) participants, and erosion was present in 32 (11.9%) participants. The median (IQR) SQDT sum score was 2 (0-4). Double contour scores at the 1 ^st MTP, knee, and 2 ^nd MTP contributed most to the SQDT sum score, followed by 1 ^st MTP tophus. There were no significant correlations between screening serum urate concentrations and elementary ultrasound lesion or SQDT sum scores (r= -0.12 to 0.06, P>0.05 for all comparisons). In the site-by-site analysis of individual joints, double contour was associated with synovial hypertrophy at the 1 ^st and 2 ^nd MTP, and tophus was associated with erosion, synovial hypertrophy, and power Doppler activity at the 1 ^st MTP (Table 2).

Conclusions: Definite musculoskeletal ultrasound features of gout can be identified in more than one third of people with asymptomatic hyperuricemia. However, the amount of MSU crystal deposition on ultrasound, assessed using the OMERACT gout ultrasound scoring system, is low. In asymptomatic hyperuricemia without clinical evidence of gout, ultrasound features of gout are associated with subclinical joint damage and inflammation.

REFERENCES: [1] Christiansen SN, Filippou G, Scire CA, et al. Consensus-based semi-quantitative ultrasound scoring system for gout lesions: Results of an OMERACT Delphi process and web-reliability exercise. Semin Arthritis Rheum. 2021;51:644-9.

Acknowledgments: NIL.

Disclosure of Interests: Sarah Stewart: None declared, Greg Gamble: None declared, William Taylor: None declared, Andrew Harrison: None declared, Tony Merriman: None declared, Borislav Mihov: None declared, Anne Horne: None declared, Isabel Su: None declared, Adwoa Dansoa Tabi-Amponsah: None declared, Lisa Stamp: None declared, Janine Haslett: None declared, Tristan Pascart Novartis, Novartis, PK Med, Horizon Pharmaceuticals (Amgen), Variant Bio, Mariano Andres Grunenthal labs, María-Luisa Peral-Garrido Pfizer, UCB, Tuhina Neogi Sobi, Eleonora Norkuviene: None declared, Janitzia Vazquez Mellado: None declared, John D. FitzGerald: None declared, Lene Terslev Novartis, UCB, Janssen, Hilde Berner Hammer AbbVie, UCB, Novartis, Till Uhlig UCB, Galapagos, Pfizer, Maria-Antonietta D’Agostino: None declared, Julia Martin: None declared, Mingshu Sun Simcere Pharma,, Changgui LI: None declared, Nicola Dalbeth Novartis, Horizon, Arthrosi, SK Chemicals, Horizon, Selecta, Arthrosi, LG Chem, JPI, PTC Therapeutics, Protalix, Unlocked Labs, Hikma, Dexcel Pharma, Shanton Pharma, Sobi, Avalo, Biomarin, Crystalys, Convergence Bio, Implicit, Medcryst, Arthrosi.