Corticosteroids Added to Initial Intravenous Immunoglobulin Treatment for the Prevention of Coronary Artery Abnormalities in High‐Risk Patients With Kawasaki Disease

BACKGROUND Randomized controlled trials previously provided different conclusions about the superiority of adding corticosteroids to initial intravenous immunoglobulin treatment for the prevention of coronary artery abnormalities in patients with Kawasaki disease (KD). To further assess this issue, we analyzed large‐scale data from nationwide KD surveys in Japan, where combination treatment (corticosteroids added to initial standard intravenous immunoglobulin treatment) has become commonly used for patients at high risk for KD. METHODS AND RESULTS Standard intravenous immunoglobulin treatment and combination treatment were compared using data from time periods with and without combination treatment. Outcome measures were coronary artery abnormalities and initial intravenous immunoglobulin treatment failure. Hospitals where ≥20% of patients received combination treatment were identified, and treatment and control groups were selected via matching by age, sex, illness day at initial treatment, and KD recurrence. Matched group selection and subsequent analyses were conducted 1000 times to minimize sampling bias and potential confounders (bootstrapping). From 115 hospitals, 1593 patients with KD in the treatment group and 1593 controls were selected for each of the 1000 sample iterations. The median proportion of patients who developed coronary artery abnormalities among the treatment group and controls were 4.6% (95% CI, 3.8%–5.8%) and 8.8% (95% CI, 7.5%–10.0%), respectively: an estimated risk ratio of 0.53 (0.41–0.67). A median of 14.1% (95% CI, 12.4%–15.9%) of the patients in the treatment group and 21.7% (95% CI, 19.8%–23.4%) in the controls had treatment failure: an estimated risk ratio of 0.65 (0.56―0.75). CONCLUSIONS Combination treatment reduced coronary artery abnormality risk by an estimated 47% and treatment failure by 35%. Multiple‐dose corticosteroids may provide benefit in selected patients at high risk for KD.