Epidemiologic features of Kawasaki disease in acute stages in Taiwan, 1997–2010: Effect of different case definitions in claims data analysis

BACKGROUND: Kawasaki disease is the leading cause of pediatric acquired cardiac disease in many industrialized countries. The aim of this study was to estimate the incidence of Kawasaki disease in acute stages in Taiwan, by linking the diagnosis code to medication and comparing the differences in epidemiological features with those of previous reports that used the diagnosis code alone. METHODS: We searched the National Health Insurance Research Database from 1997 to 2010. For the International Classification of Diseases, Ninth Revision (ICD-9) set, all inpatients with a main diagnosis of Kawasaki disease (ICD-9, 446.1) were retrieved. For the ICD-9 + intravenous immunoglobulin (IVIG) set, Kawasaki disease in acute stages was defined as the disease stages requiring IVIG. The epidemiologic features were calculated and compared by both methods. RESULTS: The incidence rates for children under 5 years ranged from 21.5 to 68.5 per 100,000 person-years (average 49.1) for the ICD-9 + IVIG set and from 48.5 to 82.8 per 100,000 person-years (average 74.9) for the ICD-9 set. Significant discrepancy in peak season estimation occurred in summer. The 5-year recurrence rate was 1.1% for the ICD-9 + IVIG set and 4.5% for the ICD-9 set. The coronary complication rates were around 7.24% (ICD-9 + IVIG) and 6.48% (ICD-9). CONCLUSION: Discrepancies occurred when different case definitions were used in claims data analysis. Previous reports might have overestimated the incidence, recurrence rate, and complication rate in older children. The new method might slightly underestimate them. The true incidence might lie in between.