Little is known whether 2-g/kg IVIG is necessary for older children with Kawasaki disease (KD), because they could have more complications and financial burden. The purpose of this study was to compare outcomes between high- and low-dose IVIG in KD children with higher body weight (25 kg or more), using a national inpatient database in Japan from 2010 to 2017. We identified those receiving 2-g/kg and 1-g/kg IVIG as an initial treatment. Outcomes included the proportions of coronary artery abnormality (CAA) formation, IVIG resistance, adverse effects, length of stay, and medical costs. A propensity score matching analysis was conducted to compare the outcomes between the groups. We identified 1332 patients with KD and created 4:1 propensity score–matched pairs between high- and low-dose IVIG groups. There were no significant differences in the proportions of CAA (5.3% vs. 4.1%; p = 0.587), IVIG resistance, and length of stay. Medical costs were significantly higher in the high-dose group than in the low-dose group (p < 0.001). Conclusion: No significant difference was shown between the high- and low-dose IVIG groups in the proportions of outcomes, while medical costs were higher in the high-dose group. Further studies are needed to ascertain the appropriate IVIG dose in older patients with KD.What is Known:• For treatments of Kawasaki disease at any age in the acute phase, 2-g/kg single-dose intravenous immunoglobulin and aspirin have been the most recommended to reduce fever early and prevent complications of coronary artery abnormalities.What is New:• There was no significant difference in outcomes between children with Kawasaki disease weighing ≥ 25 kg treated with high-dose or low-dose IVIG in terms of coronary artery abnormalities, IVIG resistance, adverse effects, and length of stay, except for medical costs.
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