A new magnetic resonance imaging scoring system is a reliable method for assessing joint damage in patients with juvenile idiopathic arthritis.

Moreover, the adult-targeted Rheumatoid Arthritis MRI Score (RAMRIS), previously considered unusable in pediatric image studies because of the "peculiarities of the growing skeleton," was also moderately well correlated with clinical indicators of disease, wrote Dr. Clara Malattia and her colleagues in the Annals of Rheumatic Diseases.

Dr. Malattia of the Istituto G Gaslini in Genoa, Italy, and her colleagues looked at 66 patients, of whom 51 were females, who had juvenile idiopathic arthritis (JIA) involving the wrist. Study participants were recruited consecutively from the researchers’ institution between June 2006 and June 2008.

The patient’s clinically more affected wrist was assessed with MRI, radiography, and clinical assessment (Ann Rheum Dis. 2010 [doi:10.1136/ard.2009.126862]).

Two readers, who were blinded to which patient’s MRIs they were evaluating, then applied the new, pediatric scoring system. Bone erosions were scored at 15 sites within the carpus according to a 0-4 scale, with 0 being equivalent to no erosion; 1 signifying between erosion of 1%-25% of the wrist; 2 signifying erosion of 26%-50%, 3 signifying between 51%-75% erosion, and 4 meaning 76%-100% erosion.

Bone marrow edema was evaluated using a 0-2 scale (with 0 signifying no edema; 1 signifying edema of less than 50% of the bone; and 2 meaning edema of 50% or more of the bone).

Finally, synovitis was assessed using the standard Rheumatoid Arthritis MRI Scoring System.

"As the inter-reader agreement was excellent, the independent scores of the two observers for each MRI were averaged, and this average was used for the analyses of the construct validity," wrote the researchers.

The existing, entire adult RAMRIS system also was completed for all patients.

At baseline, 55 out of the total 66 patients (83.3%) patients had erosions detected by MRI (only 23 of which were detected on radiography). Bone marrow edema was also seen in 55 of the 66 patients (83.3%), and synovitis was detected in 60 of the 66 patients (90.9%).

The authors then calculated the Spearman’s rank correlation between each pediatric MRI score and several clinical indicators. A correlation between 0.40-0.59 was considered moderate, correlations of 0.60-0.79 were considered high, and correlations 0.80 and greater were considered very high.

The pediatric MRI erosion score registered significant, moderate correlation (0.47) with the Juvenile Arthritis Damage Index Articular (JADI-A) score (P less than .0001), as well as a moderate (0.55) significant correlation with the Sharp/van der Heijde score for reading radiographs (P less than .0001).

The pediatric MRI bone edema score correlated highly (0.66) with the Sharp/van der Heijde score (P less than 0.0001), and registered moderate correlation (0.40) with the JADI-A (P = .001).

On the other hand, there was also high correlation (0.66) between the RAMRIS bone marrow edema score and the Sharp/van der Heijde score (P less than .0001), as well as between the RAMRIS bone erosion score and the Sharp/van der Heijde score (0.60, P less than .0001).

The synovitis score correlated moderately but significantly with the physician’s global assessment, the swollen joint count, and the Juvenile Arthritis Disease Activity Score for 71 joints (JADAS-71).

The authors then assessed the scale’s sensitivity to change by assessing 39 follow-up MRIs completed a median of 1.2 years after the index scan.

They found that among the 22 patients who had improved according to the American College of Rheumatology Pediatric 30 criteria, there was a significant but small decrease on the pediatric bone marrow edema score, a non-significant decrease in the RAMRIS bone marrow edema score, and a significant, small decrease on the synovitis score.

Meanwhile, the 17 patients who did not improve according to clinical assessment were scored as having a significant increase on the pediatric erosion scale, as well as on the RAMRIS erosion scores.

"MRI bone erosions progressed significantly at 1-year follow-up scans, but the responsiveness to change of the pediatric erosion score was poor," wrote the authors.

They postulated that this might be because the images were read without reference to the baseline scans.

Nevertheless, "a major limitation of the proposed scale is the lack of grading of erosive changes affecting less than 25% of the bone, which may hamper responsiveness to change over time," they added.

"The proposed pediatric-targeted MRI scoring system is a reliable and valid method for assessing disease activity and damage in JIA, and therefore could represent a useful framework for further development of MRI assessment of JIA," wrote the authors.

"Further work, especially in a longitudinal setting, is required," they added.

The authors stated that they had no competing interests in relation to this study.

Novel System Reliable for Scoring MRIs in Juvenile Arthritis