The incidence of pediatric rheumatic diseases: results from the Canadian Pediatric Rheumatology Association Disease Registry

Abstract

Objective: To determine the incidence of rheumatic diseases in children, and the frequency of musculoskeletal disorders seen by pediatric rheumatology specialists in Canada.

Methods: Applying standardized disease definitions and disease codes modified from ICD-9, members of the Canadian Pediatric Rheumatology Association from 13 centers in all 10 provinces of Canada registered all new patients seen between May 1, 1991 and April 30, 1993. Patient data included age, sex, ethnicity, date of birth, date of disease onset, date of diagnosis, and diagnostic codes (more than one diagnosis could be entered). To minimize the bias of right censoring, only data from patients with disease onset between May 1, 1991 and October 31, 1992 were used to estimate disease incidence.

Results: 3362 records totalling 3683 diagnoses (92 separate diagnoses) were registered. Median referral rate per year to a pediatric rheumatology center was 26 per 100,000 children at risk. The frequency of diseases seen was 23.3% for all forms of chronic arthritis, 6.5% for connective tissue diseases, and 6.1% for all forms of vasculitis. The minimum incidence rates per 100,000 children at risk per year calculated from the whole registry were: all forms of chronic arthritis 4.08 (95% CI: 3.62, 4.60), systemic lupus erythematosus 0.28 (0.18, 0.45), and dermatomyositis 0.15 (0.09, 0.29). Substantially higher figures were obtained if the figures were calculated excluding the 2 provinces (Alberta and Quebec) that had disproportionately low referral rates.

Conclusion: Pediatric rheumatologists see children with a wide variety of diseases. It is important that pediatric rheumatology training reflects this and does not focus exclusively on the classical inflammatory arthropathies. The minimum incidence data show there are substantial numbers of children developing potentially lifelong chronic rheumatic diseases each year in Canada. These data should be helpful in planning the delivery of pediatric rheumatology services not only in Canada, but also in other developed countries.