To validate the Pediatric Arthritis Ultrasound Scoring System for the knee joint (PAUSS-knee) in children with juvenile idiopathic arthritis (JIA).
Children with JIA prospectively received a musculoskeletal ultrasound (MSUS) examination of the knee and a physical examination to determine presence/absence of clinical arthritis were enrolled in this study. MSUS images were scored using the PAUSS-knee, a semiquantitative MSUS scoring system (0-normal to 3-severe) for B-mode and Power Doppler-mode. A subset of participants in addition to MSUS also received an MRI of the knee. MRI was scored according to the combined Juvenile Arthritis MRI Scoring (JAMRIS) system. Spearman's correlations (rs) were used to calculate the associations between variables. Test characteristics of the PAUSS-knee were calculated with MRI as reference standard. Inflammatory biomarkers were assessed in synovial fluid from involved knees.
Eighty children with JIA contributed 112 MSUS knees and 25 MRIs of the knee. Forty-one percent (n=46) of the knees had clinical evidence of arthritis. The B-mode PAUSS-knee score moderately correlated with arthritis determined clinically (rs=0.54, p<0.001), and strongly correlated with the JAMRIS score (rs=0.75, p<0.001). Compared to MRI, the area under the curve for the B-mode PAUSS-knee was 0.92. For a cutoff >1 the B-mode PAUSS-knee had a sensitivity of 83% and specificity of 82%. Biomarker analysis indicates IL-2R levels correlate with PAUSS score.
Our data indicates that PAUSS-knee has excellent diagnostic test accuracy for the diagnosis of arthritis when compared to MRI. The PAUSS-knee has the potential to effectively inform JIA medical decision making in real-time.