Evaluating joint-space narrowing and cartilage loss in rheumatoid arthritis using MRI (Arthritis Research & Therapy)

IntroductionMagnetic resonance imaging (MRI) has been shown to be superior to radiography (XR) for assessing synovitis, osteitis and bone erosion in rheumatoid arthritis (RA), particularly in clinical trials. However, relatively little has been reported on MRI`s ability to evaluate articular cartilage loss, or joint-space narrowing (JSN), in the hands and wrists. In a previous study, we adapted the nine-point Genant-modified Sharp XR-JSN score for use with MRI (MRI-JSN). In this study we compare MRI-JSN to XR-JSN using images from two multi-center clinical trials. Methods: Baseline XR and 1.5-Tesla MR images of one hand and wrist from each of 47 subjects with RA enrolled in one of two multi-center clinical trials were evaluated using the XR-JSN and MRI-JSN methods by a single radiologist experienced in the two methods. Radiographs and MR images were read independently on different occasions. Results: A total of 575 of 611 joints were compared (1 metacarpophalangeal joint of the thumb and 35 proximal interphalangeal joints were outside the MRI field of view and could not be assessed). 22 (47%) subjects showed JSN with both XR and MRI. 25 (53%) subjects showed no JSN with either method. No subject showed JSN with only one or the other method. MRI showed high agreement with XR (intra-class correlation coefficient = 0.83). Sensitivity of MRI for JSN, using XR as the gold standard, was 0.94; specificity was 0.91, accuracy was 0.91, positive predictive value was 0.64 and negative predictive value was 0.99. Conclusions: This validation exercise suggests that MRI JSN scoring may offer a viable alternative to XR JSN scoring in multi-center clinical trials of RA. However, MRI`s relative longitudinal sensitivity to change and ability to discriminate therapeutic effect on JSN were not evaluated in this study.