Development and initial validation of a radiographic scoring system for the hip in juvenile idiopathic arthritis.

OBJECTIVE: To develop and validate a radiographic scoring system for the assessment of radiographic damage in the hip joint in patients with juvenile idiopathic arthritis (JIA).
METHODS: The Childhood Arthritis Radiographic Score of the Hip (CARSH) assesses and scores these radiographic abnormalities: joint space narrowing (JSN), erosion, growth abnormalities, subchondral cysts, malalignment, sclerosis of the acetabulum, and avascular necrosis of the femoral head. Score validation was accomplished by evaluating reliability and correlational, construct, and predictive validity in 148 JIA patients with hip disease who had a total of 381 hip radiographs available for study.
RESULTS: JSN was the most frequently observed radiographic abnormality, followed by erosion and sclerosis of the acetabulum. The least common abnormalities were avascular necrosis, growth abnormalities, and malalignment. Interobserver and intraobserver reliability on baseline and longitudinal score values and on score changes was good, with intraclass correlation coefficients ranging from 0.76 to 0.98. Early score changes, but not absolute baseline score values, were moderately correlated (r(s) > 0.4) with clinical indicators of disease damage at last followup observation, thereby demonstrating that the CARSH has good construct and predictive validity. The amount of structural damage in the hip radiograph at last followup observation was predicted better by baseline to 1-year score change (r(s) = 0.66; p < 0.0001) than by absolute baseline score values (r(s) = 0.40; p = 0.002).
CONCLUSION: Our results show that the CARSH is reliable and valid for the assessment of radiographic hip damage and its progression in patients with JIA.