Predicting unfavorable long-term outcome in juvenile idiopathic arthritis: results from the Nordic cohort study

Abstract

Background: The aim was to develop prediction rules that may guide early treatment decisions based on baseline clinical predictors of long-term unfavorable outcome in juvenile idiopathic arthritis (JIA).

Methods: In the Nordic JIA cohort, we assessed baseline disease characteristics as predictors of the following outcomes 8 years after disease onset. Non-achievement of remission off medication according to the preliminary Wallace criteria, functional disability assessed by Childhood Health Assessment Questionnaire (CHAQ) and Physical Summary Score (PhS) of the Child Health Questionnaire, and articular damage assessed by the Juvenile Arthritis Damage Index-Articular (JADI-A). Multivariable models were constructed, and cross-validations were performed by repeated partitioning of the cohort into training sets for developing prediction models and validation sets to test predictive ability.

Results: The total cohort constituted 423 children. Remission status was available in 410 children: 244 (59.5%) of these did not achieve remission off medication at the final study visit. Functional disability was present in 111/340 (32.7%) children assessed by CHAQ and 40/199 (20.1%) by PhS, and joint damage was found in 29/216 (13.4%). Model performance was acceptable for making predictions of long-term outcome. In validation sets, the area under the curves (AUCs) in the receiver operating characteristic (ROC) curves were 0.78 (IQR 0.72-0.82) for non-achievement of remission off medication, 0.73 (IQR 0.67-0.76) for functional disability assessed by CHAQ, 0.74 (IQR 0.65-0.80) for functional disability assessed by PhS, and 0.73 (IQR 0.63-0.76) for joint damage using JADI-A.

Conclusion: The feasibility of making long-term predictions of JIA outcome based on early clinical assessment is demonstrated. The prediction models have acceptable precision and require only readily available baseline variables. Further testing in other cohorts is warranted.

Keywords: Disease activity; Juvenile idiopathic arthritis; Outcome research; Prediction.

Fig. 1

Correlations between baseline variables. Lines are drawn only between pairs of baseline variables for which the sample Spearman correlation coefficient is ≥ 0.50. Baseline variables without correlation ≥0.50 are not included in the figure. RF, rheumatoid factor; VAS, visual analogue scale; GA, global assessment; CHAQ, Childhood Health Assessment Questionnaire

Fig. 2

Receiver operating characteristic (ROC) curves for the four unfavorable clinical outcomes in the total cohort. Non-achievement of remission off medication; CHAQ, Childhood Health Assessment Questionnaire; PhS, Physical Summary Score; JADI-A, Juvenile Arthritis Damage Index-Articular

Fig. 3

Receiver operating characteristic (ROC) curves for the four unfavorable clinical outcomes in the validation sets. The colored lines are the mean ROC curves for the 100 different realizations of the partitioning of the cohort into training sets and validation sets (thin gray curves). a Not in remission. b Childhood Health Assessment Questionnaire (CHAQ) >0. c Physical Summary Score (PhS) <40. d Juvenile Arthritis Damage Index-Articular (JADI-A) >0