Carpal erosions in children with juvenile idiopathic arthritis: repeatability of a newly devised MR-scoring system

Background: Juvenile idiopathic arthritis (JIA) is characterized by synovial inflammation, with potential risk of developing progressive joint destruction. Personalized state-of-the-art treatment depends on valid markers for disease activity to monitor response; however, no such markers exist. Objective: To evaluate the reliability of scoring of carpal bone erosions on MR in children with JIA using two semi-quantitative scoring systems. Materials and methods: A total of 1,236 carpal bones (91 MR wrist examinations) were scored twice by two independent pediatric musculoskeletal radiologists. Bony erosions were scored according to estimated bone volume loss using a 0–4 scale and a 0–10 scale. An aggregate erosion score comprising the sum total carpal bone volume loss was calculated for each examination. Results: The 0–4 scoring system resulted in good intra-reader agreement and moderate to good inter-observer agreement in the assessment of individual bones. Fair and moderate agreement were achieved for inter-reader and intra-reader agreement, respectively, using the 0–10 scale. Intra- and particularly inter-reader aggregate score variability were much less favorable, with wide limits of agreement. Conclusion: Further analysis of erosive disease patterns compared with normal subjects is required, and to facilitate the development of an alternative means of quantifying disease.