Validity of an ultrasonographic joint-specific scoring system in juvenile idiopathic arthritis: a cross-sectional study comparing ultrasound findings of synovitis with whole-body magnetic resonance imaging and clinical assessment.

OBJECTIVE

To assess the validity of an ultrasonographic scoring system in juvenile idiopathic arthritis (JIA) by comparing ultrasound detected synovitis with whole-body MRI and clinical assessment of disease activity.

METHODS

In a cross-sectional study, 27 patients with active JIA underwent clinical 71-joints examination, non-contrast enhanced whole-body MRI and ultrasound evaluation of 28 joints (elbow, radiocarpal, midcarpal, metacarpophalangeal 2-3, proximal interphalangeal 2-3, hip, knee, tibiotalar, talonavicular, subtalar and metatarsophalangeal 2-3). One rheumatologist, blinded to clinical findings, performed ultrasound and scored synovitis (B-mode and power Doppler) findings using a semiquantitative joint-specific scoring system for synovitis in JIA. A radiologist scored effusion/synovial thickening on whole-body MRI using a scoring system for whole-body MRI in JIA. At patient level, associations between ultrasound synovitis sum scores, whole-body MRI effusion/synovial thickening sum scores, clinical arthritis sum scores, and the 71-joints Juvenile Arthritis Disease Activity Score (JADAS71) were calculated using Spearman's correlation coefficients (r). To explore associations at joint level, sensitivity and specificity were calculated for ultrasound using whole-body MRI or clinical joint examination as reference.

RESULTS

Ultrasound synovitis sum scores strongly correlated with whole-body MRI effusion/synovial thickening sum scores (r=0.74,p<0.01) and the JADAS71 (r=0.71,p<0.01), and moderately with clinical arthritis sum scores (r=0.57,p<0.01). Sensitivity/specificity of ultrasound in detecting synovitis were 0.57/0.96 and 0.55/0.96 using whole-body MRI or clinical joint examination as reference, respectively.

CONCLUSION

Our findings suggest that ultrasound is a valid instrument to detect synovitis, and that ultrasound synovitis sum scores can reflect disease activity and may be an outcome measure in JIA.