Description of active joint count trajectories in juvenile idiopathic arthritis
Roberta A Berard1, George Tomlinson1, Xiuying Li1
1From Western University; Children's Hospital, London Health Sciences Centre, London; Division of Clinical Decision Making and Health Care, Toronto General Research Institute, University Health Network; Division of Rheumatology, the Hospital for Sick Children; Cell Biology Program, the Hospital for Sick Children Research Institute; Department of Pediatrics, Department of Health Policy, Management and Evaluation, Dalla Lana School of Public Health, Department of Immunology, and the Department of Medical Science, University of Toronto; Institute for Work and Health, and Division of Rheumatology, Mount Sinai Hospital; Department of Medicine, University Health Network and Mount Sinai Hospital, Toronto, Ontario; University of Manitoba; Children's Hospital, Health Sciences Centre, Winnipeg, Manitoba; University of Saskatchewan, Saskatoon, Saskatchewan, Canada.R.A. Berard, MD, MSc, Western University, Children's Hospital, London Health Sciences Centre; G. Tomlinson, PhD, Division of Clinical Decision Making and Health Care, Toronto General Research Institute, University Health Network, and the Department of Health Policy, Management and Evaluation, and the Dalla Lana School of Public Health, University of Toronto, and the Department of Medicine, University Health Network and Mount Sinai Hospital; X. Li, MD, BSc, Division of Clinical Decision Making and Health Care, Toronto General Research Institute, University Health Network; K. Oen, MD, University of Manitoba, Children's Hospital, Health Sciences Centre; A.M. Rosenberg, MD, University of Saskatchewan; B.M. Feldman, MD, MSc, Division of Rheumatology, the Hospital for Sick Children, and the Department of Pediatrics, Department of Health Policy, Management and Evaluation, and the Dalla Lana School of Public Health, University of Toronto; R.S.M. Yeung, MD, PhD, Division of Rheumatology, the Hospital for Sick Children, and Department of Pediatrics, Department of Immunology, and Department of Medical Science, University of Toro
Objective:
To describe the trajectories of longitudinal joint disease activity in juvenile idiopathic arthritis (JIA), and to examine associations of clinical and laboratory characteristics with the identified trajectories.
Methods:
A retrospective cohort study at 2 Canadian centers was performed. The longitudinal trajectories of active joint counts were described in a proof-of-concept study using a latent growth curve analysis. Baseline patient characteristics were compared across trajectory groups.
Results:
Data were analyzed on 659 children diagnosed with JIA between March 1980 and September 2009. The median age at diagnosis was 10.0 years (interquartile range 3.7-13.4) and 61% (402/659) were female. The International League of Associations for Rheumatology (ILAR) diagnoses were as follows: oligoarthritis (36%), enthesitis-related arthritis (20%), rheumatoid factor (RF)-negative polyarthritis (13%), undifferentiated arthritis (12%), psoriatic arthritis (8%), systemic arthritis (7%), and RF-positive polyarthritis (4%). Based on the trajectories of their active joint counts, the 659 patients were each classified in 1 of 5 latent classes (which can be described as high decreasing, moderate increasing, persistent moderate, persistent low, and minimal joint activity). These latent classes were clinically and statistically distinct from the ILAR categories.
Conclusion:
In this proof-of-concept study, in which we used an analytic methodology in a novel way, we identified 5 clinically and statistically distinct trajectories of disease course. The subsets of patients within each class were different from those described by the ILAR classification criteria. This successful application of this method supports its use in a chronic disease with a fluctuating course such as JIA. These methods should be expanded for the purposes of predictive modeling.
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