MRI versus conventional measures of disease activity and structural damage in evaluating treatment efficacy in juvenile idiopathic arthritis.

OBJECTIVE: To compare the American College of Rheumatology paediatric (ACRp) response criteria and conventional radiography with MRI findings in a cohort of patients with juvenile idiopathic arthritis. METHODS: Forty consecutive patients (30 girls, 10 boys; median age 10.8 years) with arthritis of the wrist starting treatment with disease-modifying antirheumatic drugs or biological agents were recruited. At 1-year follow-up the treatment response was assessed by ACRp criteria and radiographic progression using the adapted Sharp/van der Heijde method. Wrist MRIs were evaluated using both the paediatric-MRI and the OMERACT rheumatoid arthritis MRI scores. Sensitivity to change of clinical and imaging variables was assessed by standardised response mean (SRM) and relative efficiency (RE) was used to compare SRMs. RESULTS: ACRp90 responders showed a significantly higher decrease in MRI synovitis score (median change -4) than non-responders (median change 0), ACRp30-50 responders (median change 0) and ACRp70 responders (median change -1) (p=0.0006, Kruskal-Wallis test). Non-responders showed significantly higher radiographic progression than ACRp90 responders (pB=0.016). The MRI synovitis score showed a greater responsiveness to change (SRM 1.69) compared with the majority of ACR core set of variables. MRI erosion scores were less responsive than conventional radiography in detecting destructive changes (RE <1). MRI follow-up revealed no signs of inflammation in four out of 24 wrists with clinically inactive disease. CONCLUSION: Only ACRp90 responders showed a significant decrease in synovitis and the halting of structural damage, suggesting that levels of response higher than ACRp30 are more appropriate for assessing drug efficacy. The excellent responsiveness of MRI and its ability to detect subclinical synovitis make it a promising outcome measure.

Novel automated system for magnetic resonance imaging quantification of the inflamed synovial membrane volume in patients with juvenile idiopathic arthritis.

OBJECTIVE: To introduce a novel automated method for the quantification of the inflamed synovial membrane volume (SV) using magnetic resonance imaging (MRI), and to investigate its feasibility and validity in patients with juvenile idiopathic arthritis (JIA). METHODS: The tool was tested on 58 patients with JIA and wrist involvement. Thirty-six patients had a 1-year MRI followup. MRI of the clinically more affected wrist was performed using a 1.5T scanner and a Flex small coil. An algorithmic approach, based on supervised voxel classification for automatic estimation of SV in a 3-dimensional MRI, was developed. The SV was estimated as the number of positively classified voxels and then normalized by the patient's body surface (NSV). Validation procedures included the analysis of reliability, construct validity, responsiveness to change, discriminant validity, and the predictive value. RESULTS: The agreement between the automated estimation of NSV and the manual measurements was excellent (intraclass correlation coefficient 0.93, 95% confidence interval 0.79-0.98). The automatic NSV demonstrated good construct validity by yielding strong correlations with local signs of disease activity and a moderate correlation with global physician assessment of disease activity and with the Rheumatoid Arthritis Magnetic Resonance Imaging Scoring system synovitis score. NSV showed a strong responsiveness to clinical change (standardized response mean values >1) and satisfactory discriminant validity. High baseline NSV (>4.6) had high predictive value (100%) with respect to erosive progression. CONCLUSION: The proposed automated method allowed reliable quantification of NSV, which represents a promising imaging biomarker of disease activity in JIA. The automated system has the potential to improve the longitudinal assessment of JIA and to predict progressive joint destruction.