120 - Estimation of Point Values of Sacroiliac Joint MRI Lesions for the Assessment of Interventions in Juvenile Idiopathic Arthritis

Poster Board Number: 120
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Abstract Body : Introduction and Objectives: Optimal outcome measurement is vital for assessing intervention effectiveness in juvenile idiopathic arthritis (JIA) clinical trials (CT). Serology and clinical measurement tools have limited reliability, and magnetic resonance imaging (MRI) is the reference imaging modality for joint assessment in JIA. Calibration of sacroiliac joint MRI biomarkers has shown promising results as an ideal outcome measurement tool in JIA-CT. The preliminary juvenile idiopathic arthritis magnetic resonance imaging-sacroiliac joint scoring system (JAMRIS-SIJ) was developed to be used as an imaging outcome measurement for JIA-CT. Prior validation steps comprised the assessment of the JAMRIS-SIJ reliability. This study aims to determine the face validity and point value of JAMRIS-SIJ.
Materials and Methods: An adaptive multi-criteria decision analysis was performed using the 1000Minds web application. Imaging and clinical experts independently completed a conjoint analysis survey (CAS) to determine the point value of the JAMRIS-SIJ measurement items. Expert preferences were elicited by comparing JAMRIS-SIJ partial profiles, which are otherwise similar but different at two measurement items at a time, with a trade-off to select which item shows a more severe stage of inflammation or osteochondral damage. In addition, experts ranked 14 JAMRIS-SIJ full-profile image-based and score vignettes while blinded to the CAS-derived weights.
Results: The point value for inflammation domain items, osteitis (24.7%), and bone marrow edema (24.3%) reported higher group-averaged percentage weights compared to inflammation in erosion cavity (16.9%), joint space enhancement (13.1%), joint space fluid (9.1%), capsulitis (7.3%) and enthesitis (4.6%). Similarly, concerning the damage domain, ankylosis (41.3%) and erosion (25.1%) showed higher group-averaged weights compared to backfill (13.9%), sclerosis (10.7%), and fat metaplasia lesion (9.1%). Spearman correlation coefficient for the CAS and JAMRIS-SIJ score vignettes for all experts was 0.79 for inflammation and 0.80 for damage. Subgroup analysis for correlation of CAS and JAMRIS-SIJ score vignettes for rheumatologists was 0.84 for inflammation and 0.89 for damage, and for radiologists, 0.76 for inflammation and 0.71 for damage. The correlation of image vignette-derived weights among imaging experts compared to CAS-derived weights was 0.75 for inflammation and 0.90 for damage.
Conclusion/Implication: The multi-criteria decision analysis identified differences in relative weights between the JAMRIS-SIJ measurement items. Determination of the relative weights provided expert-driven score scaling and face validity for the JAMRIS-SIJ, enabling subsequent evaluation of its longitudinal construct validity. Furthermore, this evidence will inform future measurement item reduction considerations to aid JAMRIS-SIJ usability.