Background/Purpose: Although there is a consistent body of evidence supporting the use of Ultrasound (US) in Gout, several definitions for US lesions have been proposed. Recently, the OMERACT US Group has proposed a set of 4 definitions, including double contour (DC), aggregates, tophus and erosions. Objective: to evaluate intra and inter-reader reliability of the US definitions of elementary lesions in gout developed by the OMERACT US Gout Task Force.

Methods:   A reliability exercise based on the reading of US images was conducted   during the 2016 PANLAR Congress by the PANLAR US Study Group. Fourteen rheumatologists from 6 Latin American countries with different experience in US participated. US images of both normal and gouty elementary lesions were collected by 2 sonographers highly experienced in gout. The image set consisted in 70 static images and 10 videos that were displayed for 20 seconds. Participants were asked to determine the presence of any of the 4 elementary lesions in each image. Nine images was displayed twice to estimate intra-reader reliability. Statistical analysis: Intra and Inter-reader reliability was calculated by the Cohen’s kappa coefficient, considering Landis and Koch criteria (<0.2 poor, 0.21–0.4 fair, 0.41–0.6 moderate, 0.61–0.8 good, and 0.81–1 excellent). Furthermore, we stratified sonographers according to their US experience (defining High experience: >5 years of US experience and >50 US gout assessments/year).

Results: A total of 980 image assessment were performed. Aggregates was the more frequent lesions (50%), followed by Tophus (40%), DC (28%) and Erosions (27%). The mean intra-reader values were good to excellent in all lesions: DC= 0.90, aggregates = 0.86, erosions = 0.79 and tophus = 0.76. Mean Kappa inter-reader coefficients showed variability depending on the type of lesion, being moderate for aggregates (K= 0.44) and tophus (K=0.56), good for erosions (K=0.61), and excellent for DC (K=0.87). Kappa estimates and marginal distributions of specific ratings are showed in Figure 1 and Table 2. When comparing high with low experience sonographers, those with high experience showed better intra and inter-reader reliability and lower marginal heterogeneity.

Conclusion: The reliability of the new OMERACT US definitions of elementary lesions in gout varied depending on the type of lesion and evaluator experience. Ultrasonography training programs are necessary to improve the reliability of these new gout US definitions. Figure 1. Marginal distributions of specific ratings among sonographers and relation with personal experience.

Table 2. Intra-rater reliability.