Background: Although Kawasaki disease (KD) is known to cause anemia, the relationship between its prognosis and hemoglobin level is less well known.

Methods: We herein performed a secondary analysis of data from a previous study (Post-RAISE). Children aged 6 months to 2 years at the time of KD diagnosis were enrolled. Decreased hemoglobin was defined as a decrease > 10% on post-treatment day 2 compared with the level prior to the initial therapy.

Results: Of 1253 KD cases, treatment resistance was observed in 209 (17%) and was significantly more frequent in the decreased hemoglobin group (37/167 vs. 172/1086, P = 0.041). Multivariable logistic regression analysis revealed that decreased hemoglobin was associated with resistance to the initial treatment (odds ratio 1.53; 95% confidence interval 1.00-2.33; P = 0.048).