POS1101 THE OMERACT KNEE INFLAMMATION MRI SCORING SYSTEM: VALIDATION OF QUANTITATIVE METHODOLOGIES AND TRI-COMPARTMENTAL OVERLAYS BY COMPARISON WITH THE MRI OSTEOARTHRITIS KNEE SCORE
Authors: W. P. Maksymowych, J. L. Jaremko, S. Juhl Pedersen, I. Eshed, U. Weber, A. Mcreynolds, S. Wichuk, J. Paschke, R. G. Lambert
Journal: Annals of the Rheumatic Diseases (2021)

Background: Randomized controlled trials have targeted reducing the size of BML and degree of synovitis for the treatment of OA. We have developed the OMERACT Knee Inflammation MRI Scoring System (KIMRISS) and have recently refined it to maximize reliability and sensitivity to change. Innovations include electronic overlays for assessment of BML in 500 subregions, a web-based interface with direct online scoring, and real-time iterative calibration (RETIC) prior to reading exercises. Synovitis-effusion (S-E) is also scored on all consecutive sagittal slices on a web-based interface. Objectives: We aimed to test the feasibility, reliability, and responsiveness of KIMRISS versus an established method, MOAKS, in two multi-reader exercises. Methods: KIMRISS incorporates web-based graphic overlays for each of femur, tibia, and patella (range 0-500). S-E is recorded as the largest diameter perpendicular to the longest axis of this feature (range 0-100). All scores are pro-rated for a standardized number of MRI slices. In a pre-reading exercise for KIMRISS, readers scored sufficient cases in RETIC to attain scoring proficiency, pre-specified as an ICC of ≥0.80 and ≥0.70 for status and change scores of BML and S-E compared to developer reads. A new web-based scoring platform with overlays designating different subregions for scoring BML was developed for MOAKS. We compared reliability for status and change scores of BML and S-E in 2 international multi-reader exercises of baseline and one-year MRI scans from the Osteoarthritis Initiative: A. 4 expert readers and an OMERACT fellow scored 38 cases selected for MOAKS BML score ≥1. B. 7 expert readers and an OMERACT fellow scored 60 cases selected for MOAKS BML ≥3 and Kellgren-Lawrence (K-L) grade &lt;3. Reliability was assessed by intra-class correlation coefficient (ICC) and Smallest Detectable Change (SDC), responsiveness by the standardized response mean (SRM), and feasibility using the System Usability Scale (SUS scoring range 0-100). Results: For exercises A/B, subjects were 55.3%/ 26.7% male, mean(±SD) age 61.7(±9.1)/61.9(8.8) years, and radiographic K-L grade ≤2 in 39.4%/100%. Change was small in both exercises (&lt;5% of scoring range for KIMRISS and MOAKS BML and S-E) with comparable responsiveness (Table 1). Despite this, ICC for change was consistently good to very good for both BML and S-E and consistently better for KIMRISS (Table 1). Mean SUS scores were 88.2 for KIMRISS and 54.3 for MOAKS. Table 1. KIMRISS and MOAKS scores in Two International Multi-reader Exercises Method MRI feature Scores mean (SD ) SDC (% of max ) P value SRM Baseline One-year Follow up Change EXERCISE A MOAKS BML 3.6 (2.9) 3.4 (2.3) -0.2 (1.9) 1.0 (2.2%) 0.72 -0.11 Synovitis-effusion 1.3 (0.8) 1.5 (0.8) 0.2 (0.4) 0.4 (13.3%) 0.017 0.5 KIMRISS BML 15.7 (13.3) 21.2 (22.5) 5.5 (15.3) 5.6 (1.1%) 0.022 0.36 Synovitis-effusion 21.8 (12.0) 24.3 (11.9) 2.5 (7.4) 2.8 (2.8%) 0.043 0.34 EXERCISE B MOAKS BML 4.2 (2.6) 3.7 (2.4) -0.5 (2.1) 1.1 (2.4%) 0.083 -0.24 Synovitis-effusion 1.2 (0.7) 1.3 (0.8) 0.0 (0.5) 0.4 (13.3%) 0.59 0.0 KIMRISS BML 18.0 (17.5) 15.9 (14.3) -2.1 (12.3) 5.9 (1.2%) 0.19 -0.17 Synovitis-effusion 21.8 (9.3) 22.9 (10.8) 1.1 (7.1) 2.2 (2.2%) 0.25 0.15 Intra-class Correlation Coefficients (95%CI ) Method MRI feature Exercise A Exercise B KIMRISS status KIMRISS change BML 0.86 (0.78-0.92) 0.88 (0.81-0.93) 0.80 (0.70-0.87) 0.72 (0.64-0.80) MOAKS status MOAKS change BML 0.71 (0.46-0.85) 0.76 (0.64-0.85) 0.67 (0.56-0.77) 0.69 (0.60-0.78) KIMRISS status KIMRISS change Synovitis-effusion 0.88 (0.81-0.93) 0.87 (0.79-0.92) 0.75 (0.52-0.86) 0.87 (0.82-0.91) MOAKS status MOAKS change Synovitis-effusion 0.66 (0.4-0.79) 0.52 (0.36-0.67) 0.65 (0.52-0.75) 0.48 (0.37-0.60) Conclusion: The KIMRISS method for scoring BML and Synovitis-Effusion scores highly for feasibility and demonstrates consistently high reliability when compared to MOAKS. Further validation for responsiveness is necessary in cases with greater change in MRI features than in the OAI dataset. Disclosure of Interests: None declared.