Diagnostic utility and reliability of the OMERACT semi-quantitative ultrasound scoring system in gout: a...

To evaluate the diagnostic performance and reliability of the OMERACT semi-quantitative ultrasound scoring system compared with a binary scoring system for the diagnosis of gout in a multicenter setting.

This multicenter, retrospective observational study included 912 patients (457 with gout and 455 with non-gout inflammatory arthritis) from two institutions. All participants underwent standardized musculoskeletal ultrasound examinations of the hands and feet. Four elementary lesions (double contour sign, aggregates, tophus, and bone erosion) were assessed using both a binary classification (present/absent) and the OMERACT semi-quantitative scoring system (grades 0-3). Diagnostic accuracy was analyzed using receiver operating characteristic (ROC) curves against the 2015 ACR/EULAR gout classification criteria. Inter- and intra-observer reliability were assessed using weighted kappa (κ) statistics in 100 randomly selected cases.

The OMERACT semi-quantitative score demonstrated superior diagnostic accuracy (AUC 0.988, 95% CI 0.982-0.994) compared to the binary score (AUC 0.929, 95% CI 0.914-0.943; P < 0.001). At an optimal cutoff value of 1.5, the semi-quantitative score achieved a sensitivity of 96.5% and a specificity of 97.1%. Furthermore, the semi-quantitative system exhibited excellent reliability, with inter-observer and intra-observer weighted κ values of 0.85 and 0.91, respectively, outperforming the binary system (inter-observer κ = 0.75). Stratified analysis confirmed consistent diagnostic performance across participating centers (P = 0.1907).

The OMERACT semi-quantitative ultrasound scoring system provides significantly higher diagnostic accuracy and reproducibility than the binary system for diagnosing gout. Its robustness and consistency across multicenter settings support its utility as a standardized, non-invasive tool for clinical practice and research. Key Points • The OMERACT semi-quantitative ultrasound scoring system demonstrated superior diagnostic accuracy for gout compared to the binary system (AUC 0.988 vs. 0.929). • The system achieved excellent inter- and intra-observer reliability (κ = 0.85 and 0.91), confirming strong reproducibility across centers. • This multicenter study provides robust real-world evidence supporting the generalizability and clinical applicability of the OMERACT scoring system. • The semi-quantitative scoring system offers a standardized, non-invasive, and highly reliable tool for diagnosing and monitoring gout in clinical and research settings.