Juvenile idiopathic arthritis of the knee: is contrast needed to score disease activity when using an augmented MRI protocol comprising PD-weighted sequences?

ObjectiveTo compare unenhanced versus enhanced knee joint magnetic resonance imaging (MRI) to assess disease activity of juvenile idiopathic arthritis (JIA). MethodsFifty-three knee joint MRI examinations were performed on a 3-Tesla system in 27 patients (age: 11.40 & PLUSMN; 3.61 years; 21 females, 6 males). MRI protocols comprised PD-weighted sequences in addition to the widely used standard protocol. JIA subgroups comprised oligoarticular arthritis (n = 16), extended oligoarthritis (n = 6), rheumatoid factor-negative polyarticular arthritis (n = 3), enthesitis-related arthritis (n = 1), and psoriatic arthritis (n = 1). MR images were retrospectively analyzed by 3 experienced radiologists in two readings, using JAMRIS (juvenile arthritis MRI scoring) system and a modified IPSG (international prophylaxis study group) classification. In the first reading session, only unenhanced MR images were evaluated. In a second reading session, all images before and after contrast medium application were included. In order to avoid bias, an interval of at least 2 weeks was set between the two readings. The clinical JADAS10 (juvenile arthritis disease activity score) was calculated including clinical assessment and laboratory workup and correlated with MRI scores. Statistical analysis comprised Pearson's correlation for correlating two scoring results of unenhanced and the enhanced MRI, intra-class correlation coefficient (ICC) for inter- and intra-reader agreement. Diagnostic accuracy was calculated using ROC (receiver operating characteristics) curve analysis. ResultsInter-reader agreement determined by ICC for unenhanced and enhanced MRI scores for IPSG was moderate (0.65, 95% CI 0.51-0.76, and 0.62, 95% CI 0.48-0.75) and high for JAMRIS (0.83, 95% CI 0.75-0.89, and 0.82, 95% CI 0.74-0.89). Intra-reader agreement was good to very good for JAMRIS (0.85 95% CI 0.81-0.88, 0.87 95% CI 0.83-0.89 and 0.96 95% CI 0.92-0.98) and IPSG (0.76 95% CI 0.62-0.86, 0.86 95% CI 0.77-0.92 and 0.92 95% CI 0.86-0.96). Scores of unenhanced MRI correlated with contrast-enhanced MRI: JAMRIS (r = 0.97, R-2 = 0.93, p < 0.01), modified IPSG (r = 0.95, R-2 = 0.91, p < 0.01). When using JADAS10 as a reference standard, moderate accuracy for both unenhanced and enhanced MRI scores was noted: JAMRIS (AUC = 0.68, 95% CI 0.51-0.85, and AUC = 0.66, 95% 0.49-0.82), IPSG score (AUC = 0.68, 95% 0.50-0.86, and AUC = 0.61, 95% 0.41-0.81). ConclusionsOur results suggest that contrast agent application could be omitted in JIA patients with an augmented knee MRI protocol comprising PD-weighted sequence.

Automated summary

This study compares unenhanced and enhanced knee joint MRI in evaluating the disease activity of JIA. The results suggest that an augmented MRI protocol with PD-weighted sequences can be used in JIA patients without the need for contrast agent application.