Objectives: To determine whether clinical, laboratory or Magnetic Resonance Imaging (MRI) measures differentiate Juvenile Idiopathic Arthritis (JIA) from other forms of active childhood arthritis.
Materials and methods: We 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.
Results: Forty-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).
Conclusions: The 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.
Keywords: Childhood arthritis; Juvenile Idiopathic Arthritis; Knee joint; Magnetic Resonance Imaging; Synovitis.