Preliminary validation of a web-based MRI scoring system for children with chronic nonbacterial osteomyelitis (ChRonic nonbacterial Osteomyelitis Magnetic Resonance Imaging Scoring: CROMRIS).

Background: The ChRonic nonbacterial Osteomyelitis Magnetic Resonance Imaging Scoring (CROMRIS) tool was developed to assess specific characteristics of bone and soft tissue inflammation on MR images of patients with CNO; however, this tool was labor intensive to utilize. We aimed (1) to refine and adapt this scoring method, (2) to assess the usability of this web-based CROMRIS system among radiologists and (3) to evaluate the absolute agreement of the components and summary CROMRIS scores at each body site, and the interrater reliability.

Methods: We used a qualitative, user-centered design approach involving software developers, rheumatologists, radiologists, and a patient artist to adapt the paper-based scoring system to a web-based prototype that was further refined by monthly meetings between the group members. A clickable-schematic-based CROMRIS system was developed to include all body regions: head (skull/mandible), spine, torso (clavicle, sternum, and ribs), pelvis, hands, feet, arms, and legs. Readers scored individual bone units to indicate the presence of bone marrow hyperintensity on STIR images (score 0-1), soft tissue/periosteal hyperintensity of surrounding tissue (score 0-1), and bony expansion (score 0-1), and quantified the signal size of the CNO lesion (scores 1-3 defined as < 25%, 25-50%, or > 50% of the estimated volume, respectively). The sum of these parameters for lesions detected on fluid-sensitive sequences was the CROMIS Activity Index (maximum score 720). Feedback for usability was reported with descriptive content analysis and continuous variables as means and categorical variables as percentages. Interrater reliability was assessed by free-marginal kappa (k) statistics and the intraclass correlation coefficient (ICC).

Results: The mean system usability score increased from 64.5 (below average) to 75 (above average) after user feedback. Interrater reliability for the CROMRIS Activity Index was excellent for clavicle, tibia, cervical and lumbar spines (> 0.9) and good to moderate for the remainder of the body regions. The mean kappa of each category of bones was > 0.6 demonstrating substantial interrater reliability among radiologists for the bone sites most affected by CNO, namely the long bones and clavicle.

Conclusion: The web-based CROMRIS portal developed was usable and showed substantial-moderate agreement in the total CROMRIS Activity Index total scores among experienced radiologists after self-guided learning of the atlas and video. This tool can potentially be used in future clinical trials after calibration.