Contrast-enhanced MRI features in the early diagnosis of Juvenile Idiopathic Arthritis.

objectivesTo determine whether clinical, laboratory or Magnetic Resonance Imaging (MRI) measures differentiate Juvenile Idiopathic Arthritis (JIA) from other forms of active childhood arthritis. MATERIALS AND

methodsWe prospectively collected data of 80 treatment-naïve patients clinically suspected of JIA with active non-infectious arthritis of (at least) one knee for <12 months duration. Upon presentation patients underwent clinical and laboratory assessments and contrast-enhanced MRI. MRI was not used as a diagnostic criterion.

resultsForty-four (55%) patients were clinically diagnosed with JIA, whereas in 36 (45%) patients the diagnosis of JIA was discarded on clinical or laboratory findings. MRI-based synovitis was present in 27 (61.4%) JIA patients and in 7 (19.4%) non-JIA patients (P < 0.001). Five factors (male gender, physician's global assessment of overall disease activity, joints with limited range of motion, HLA-B27, MRI-based synovitis) were associated with the onset of JIA. In multivariate analysis MRI-based synovitis proved to be independently associated with JIA (OR 6.58, 95% CI 2.36-18.33). In patients with MRI-based synovitis, the RR of having JIA was 3.16 (95% CI 1.6-6.4).

conclusionsThe presence of MRI-based synovitis is associated with the clinical onset of JIA. Physical examination could be supported by MRI, particularly to contribute in the early differentiation of different forms of non-infectious childhood arthritis. KEY POINTS: • Juvenile Idiopathic Arthritis (JIA) is a diagnosis of exclusion. • Differentiating JIA and other forms of childhood arthritis can be difficult. • MRI-techniques have substantially improved evaluation of joint abnormalities in JIA patients. • MRI-based synovitis is significantly associated with the clinical onset of JIA. • MRI could support physical examination in the early differentiation of childhood arthritis.