Kawasaki disease (KD) is a common pediatric vasculitis with rising global incidence. Associated coronary artery aneurysms (CAA) can result in significant long-term morbidity and mortality. However, our understanding of the trends in incidence along with patient and disease characteristics for North American children over the past two decades remains limited, particularly in universal health care systems. This understanding can inform healthcare resource planning and identify knowledge gaps for educational initiatives.
The objectives of this study were to: 1) compare patient, hospital and disease characteristics for children diagnosed with KD between two eras (1995-2001 and 2002-2017) and three age groups (0-4yr, 5-9yr, 10-18yr) and 2) determine trends in KD incidence across Ontario, Canada between 1995 to 2017.
We used healthcare administrative databases housed at the Institute for Clinical Evaluative Sciences (ICES) to identify a population-based cohort of Ontario children (0-18 years) diagnosed with KD during hospital admission between April 1995 and March 2017. We excluded children with previous KD diagnosis. We compared eras and age groups by Chi-squared test. We determined the annual incidence of KD in Ontario, compared by Cochrane-Armitage test.
We identified 4346 Ontario children diagnosed with KD between 1995-2017. The mean (SD) age at diagnosis was 3.4 years (± 2.9) and male:female ratio was 1.5:1. Median (IQR) length of hospital admission was 3 days (2-4) and 104 children (2.4%) required PICU admission. No child died within 90 days of diagnosis. Baseline CAA were observed in 106 children (2.4%). There was no difference in baseline CAA by era (2.3% [1995-2001] vs 2.5% [2002-2017], p=0.72). CAA were significantly more common in children aged 10-18 years (5.3% vs 2.4% [0-4yr] and 2.2% [5-9yr], p=0.03). Myo-/pericarditis occurred in 71 children (1.6%). Red blood cell transfusions were administered to 51 children (1.2%) and were significantly more common during 2002-2017 (≤0.5% vs 1.5%, p<0.001). The standardized incidence of KD increased significantly over the study period (p<0.0001), from 6.5 cases per 100,000 person-years (1995-2000) to 8.4 cases (2012-2017). Significant seasonal variation was observed; incidence was highest from November to March (OR 1.7 – 2.1, using August as reference month) and peaked in January (OR 2.1).
The incidence of KD has increased significantly over the past 20 years in Ontario, Canada which may reflect increased awareness and improved diagnosis. However, the frequency of baseline CAA has not changed. Baseline CAA are more common in children 10-18 years. This may suggest delayed diagnosis in this age group.