Normal, Weighted Summation of MRI Scores Valid for Assessing RA

For patients with rheumatoid arthritis (RA), combined magnetic resonance imaging (MRI) scores calculated by either normalized or weighted summation of individual MRI pathologies can be responsive and valid, according to results published in the Journal of Rheumatology.

The study included data from 3 large, randomized early RA trials to assess 5 methods to develop a combined score for inflammation based on RAMRIS (Outcome Measures in Rheumatology RA MRI Scoring system) bone marrow edema, synovitis, and tenosynovitis scores, plus a combined joint damage score based on erosions and joint space narrowing. The methods included unweighted summation, normalized summation, and 3 different variants of weight summation of the RAMRIS features.

The researchers examined the construct validity of the combined scores by assessing correlations to imaging, clinical, and biochemical measures. They calculated the standardized response mean and relative efficiency of each score in a validation cohort to test responsiveness.

The results indicated that all combined scores were significantly correlated to other imaging, clinical, and biochemical measures.

Compared with unweighted summation, inflammation scores combined by normalized and weighted summation had significantly higher responsiveness (unweighted summation standardized response mean, 0.62; normal summation, 0.73; weighted summation, 0.74).

The researchers found that there was a trend toward higher responsiveness for weighted summation with damage score.

“The discriminative properties of the scores need to be tested in placebo-controlled clinical trials,” the researchers wrote.

Reference

Sundin U, Østergaard M, Glinatsi D, et al. Validity and responsiveness of combined inflammation and combined joint damage scores based on the OMERACT rheumatoid arthritis MRI scoring system (RAMRIS) [published online February 15, 2019]. J Rheumatol. doi: 10.3899/jrheum.181064