Validation of the Ankle-Specific Pediatric Arthritis Ultrasound Scoring System in Children with Juvenile Idiopathic Arthritis

To validate the ankle-specific Pediatric Arthritis Ultrasound Scoring System (PAUSS-ankle) in children with juvenile idiopathic arthritis (JIA). Patients with a diagnosis of JIA prospectively underwent a standard clinical assessment and musculoskeletal ultrasound (MSUS) of one or both ankles. B-mode and Power-Doppler mode MSUS images were acquired and scored according to the PAUSS-ankle protocol. A subset of patients received a contrast-enhanced MRI (ceMRI) of the affected ankle. ceMRI scoring for synovitis was performed according to the Rheumatoid Arthritis MRI System (RAMRIS). Test characteristics of the PAUSS-ankle scores were evaluated with ceMRI as reference. Associations between the findings on physical examination, PAUSS-ankle, and RAMRIS were investigated. Thirty-two patients with JIA contributed 63 MSUS and 15 ceMRIs of the ankles. The PAUSS-ankle total B-mode score had a moderate correlation with physical examination findings (correlation (r)=0.43, p<0.001). The PAUSS-ankle B-mode score ≥1 exhibited a sensitivity of 79% and specificity of 100%, demonstrating excellent diagnostic accuracy with an area under the curve (AUC)= 0.89 (confidence intervals, CI, 0.78-1.00) while clinical assessment had a sensitivity of 57% and AUC= 0.71 (CI: 0.58-0.85). The PAUSS-ankle B-mode score had significant strong correlations (r=0.68–0.90, p<0.005) with the RAMRIS for the assessment of disease severity for each joint area and the ankle joint as a whole. Our findings demonstrate excellent diagnostic accuracy of the PAUSS-ankle in detecting the presence and severity of ankle synovitis when compared to ceMRI. The PAUSS-ankle holds significant promise as an accurate measurement that may complement current clinical standards.