To determine the predictors of sacroiliitis detected by magnetic resonance imaging (MRI) in children with enthesitis-related arthritis.
In this retrospective, longitudinal study, we retrieved clinical and laboratory data from the charts of patients with confirmed enthesitis related arthritis and evaluated their association with magnetic sacroiliitis detected at first MRI after disease onset. The MRI images of sacroiliac joints were read by 2 independent radiologists and validated against those from 25 age- and sex-matched subjects with known non-rheumatologic conditions.
We reviewed the clinical records of 20 patients with enthesitis-related arthritis for whom MRI images of sacroiliac joints were available. Five had bilateral MRI sacroiliitis, 3 unilateral sacroiliitis while 12 had no sacroiliitis. All MRI images of sacroiliiitis showed bone-marrow oedema but no erosions, sclerosis or sacroiliac enthesitis. Personal history of buttock pain or abnormal physical examination of sacroiliac joints predicted MRI sacroiliitis with a positive predictive value of 0.75 (95% confidence interval 0.35-0.95). In the absence of these clinical elements, MRI sacroiliitis was unlikely to be found (negative predictive value 0.83; 95% confidence interval 0.50-0.97).
In children with enthesitis-related arthritis the presence of buttock pain or of abnormal sacroiliac joint examination is a strong predictor of magnetic sacroiliitis.