Objective The present study was undertaken to assess the long‐term course, remission rate, and disease burden in juvenile idiopathic arthritis (JIA) 18 years after disease onset in a population‐based setting from the early biologic era. Methods A total of 510 consecutive cases of JIA with disease onset between 1997 and 2000 from defined geographic regions in Denmark, Norway, Sweden, and Finland were prospectively included in this 18‐year cohort study. At the follow‐up visit, patient‐reported demographic and clinical data were collected. Results The study included 434 (85%) of the 510 eligible JIA participants. The mean ± SD age was 24.0 ± 4.4 years. The median juvenile arthritis disease activity score in 71 joints (JADAS‐71) was 1.5 (interquartile range [IQR] 0–5), with the enthesitis‐related arthritis (ERA) category of JIA having the highest median score (4.5 [IQR 1.5–8.5], P = 0.003). In this cohort, 46% of patients still had active disease, and 66 (15%) were treated with synthetic disease‐modifying antirheumatic drugs and 84 (19%) with biologics. Inactive disease indicated by a JADAS‐71 score of <1 was seen in 48% of participants. Clinical remission off medication (CR) was documented in 33% of the participants with high variability among the JIA categories. CR was most often seen in persistent oligoarticular and systemic arthritis and least often in ERA (P < 0.001). Conclusion A substantial proportion of the JIA cohort did not achieve CR despite new treatment options during the study period. The ERA category showed the worst outcomes, and in general there is still a high burden of disease in adulthood for JIA.

BackgroundThe incidence of uveitis associated with juvenile idiopathic arthritis (JIA) varies around the world. Our aim was to investigate the incidence and predictors of uveitis in a Nordic population-based cohort.MethodsConsecutive JIA cases from defined geographical areas in Denmark, Finland, Sweden and Norway with disease onset between January 1997 to June 2000 were followed for median 98 months in this prospective longitudinal cohort study. Potential clinical and immunological predictors of uveitis were identified with logistic regression analysis.ResultsUveitis occurred in 89 (20.5%) of the 435 children with regular ophtalmologic follow-up among the 500 included. Chronic asymptomatic uveitis developed in 80 and acute symptomatic uveitis in 9 children. Uveitis developed at a median interval of 0.8 (range − 4.7 to 9.4) years after onset of arthritis. Predictors of uveitis were age < 7 years at JIA onset (Odds ratio (OR) 2.1, 95% confidence interval (CI) 1.3 to 3.5), presence of antihistone antibodies (AHA) > 15 U/ml (OR 4.8 (1.8 to 13.4)) and antinuclear antibodies (ANA) (OR 2.4 (1.5 to 4.0)). Mean combined IgM/IgG AHA was significantly higher in the uveitis group (19.2 U/ml) than in the non-uveitis group (10.2 U/ml) (p = 0.002). Young age at JIA onset predicted uveitis in girls (p < 0.001), but not in boys (p = 0.390).ConclusionEarly-onset arthritis and presence of AHA in girls, as well as presence of ANA in both genders, were significant predictors of chronic uveitis. The high incidence of uveitis in this long-term Nordic JIA cohort may have severe implications in a lifelong perspective.

In this near population-based Nordic JIA cohort we found significant differences between HLA-B27-positive boys and girls in age at disease onset, clinical signs of sacroiliitis, and ERA classification. HLA-B27 was negatively associated with longterm remission status, possibly because of its association with clinical disease characteristics, such as sacroiliitis, rather than being a general marker of persistent disease.

BackgroundThe 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).MethodsIn 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.ResultsThe 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.ConclusionThe 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.Electronic supplementary materialThe online version of this article (10.1186/s13075-018-1571-6) contains supplementary material, which is available to authorized users.