Development and External Validation of a Model Predicting New‐Onset Chronic Uveitis at Different Disease Durations in Juvenile Idiopathic Arthritis

OBJECTIVE: To develop and externally validate a prediction model for new‐onset chronic uveitis in children with juvenile idiopathic arthritis (JIA) for clinical application. METHODS: Data from the international Pharmachild registry were used to develop a multivariable Cox proportional hazards model. Predictors were selected by backward selection, and missing values were handled by multiple imputation. The model was subsequently validated and recalibrated in 2 inception cohorts: the UK Childhood Arthritis Prospective Study (CAPS) study and the German Inception Cohort of Newly diagnosed patients with juvenile idiopathic arthritis (ICON) study. Model performance was evaluated by calibration plots and C statistics for the 2‐, 4‐, and 7‐year risk of uveitis. A diagram and digital risk calculator were created for use in clinical practice. RESULTS: A total of 5,393 patients were included for model development, and predictor variables were age at JIA onset (hazard ratio [HR] 0.83 [95% confidence interval (95% CI) 0.77–0.89]), ANA positivity (HR 1.59 [95% CI 1.06–2.38]), and International League of Associations for Rheumatology category of JIA (HR for oligoarthritis, psoriatic arthritis, and undifferentiated arthritis versus rheumatoid factor–negative polyarthritis 1.40 [95% CI 0.91–2.16]). Performance of the recalibrated prediction model in the validation cohorts was acceptable; calibration plots indicated good calibration and C statistics for the 7‐year risk of uveitis (0.75 [95% CI 0.72–0.79] for the ICON cohort and 0.70 [95% CI 0.64–0.76] for the CAPS cohort). CONCLUSION: We present for the first time a validated prognostic tool for easily predicting chronic uveitis risk for individual JIA patients using common clinical parameters. This model could be used by clinicians to inform patients/parents and provide guidance in choice of uveitis screening frequency and arthritis drug therapy.