Validation of a Knowledge Transfer Tool for the Knee Inflammation MRI Scoring System for Bone Marrow Lesions According to the OMERACT Filter: Data from the Osteoarthritis Initiative.

Objective: To assess feasibility and reliability of scoring bone marrow lesions (BML) on knee magnetic resonance imaging (MRI) in osteoarthritis using the Outcome Measures in Rheumatology Knee Inflammation MRI Scoring System (KIMRISS), with a Web-based interface and online training with real-time iterative calibration.

Methods: Six readers new to the KIMRISS (3 radiologists, 3 rheumatologists) scored sagittal T2-weighted fat-saturated MRI in 20 subjects randomly selected from the Osteoarthritis Initiative data, at baseline and 1-year followup. In the KIMRISS, the reader moves a transparent overlay grid within a Web-based interface to fit bones, then clicks or touches each region containing BML per slice, to score 1 if BML is present. Regional and total scores are automatically calculated. Outcomes include the interreader intraclass correlation coefficients (ICC) and the smallest detectable change (SDC).

Results: Scoring took 3-12 min per scan and all readers rated the process as moderately to very user friendly. Despite a low BML burden (average score 2.8% of maximum possible) and small changes, interobserver reliability was moderate to high for BML status and change in the femur and tibia (ICC 0.78-0.88). Four readers also scored the patella reliably, whereas 2 readers were outliers, likely because of image artifacts. SDC of 1.5-5.6 represented 0.7% of the maximum possible score.

Conclusion: We confirmed feasibility of knee BML scoring by new readers using interactive training and a Web-based touch-sensitive overlay system, finding high reliability and sensitivity to change. Further work will include adjustments to training materials regarding patellar scoring, and study in therapeutic trial datasets with higher burden of BML and larger changes.