Changes in Hemoglobin Concentrations Post-immunoglobulin Therapy in Patients with Kawasaki Disease: A Population-Based Study Using a Claims Database in Japan.

BACKGROUND: We sought to quantify the degree of anemia after high-dose intravenous immunoglobulin (IVIG) therapy in patients with Kawasaki disease (KD) by assessing hemoglobin (Hb) dynamics and determining the risk of transfusion.

METHODS: We analyzed data from a database containing inpatient data collected from 230 hospitals in Japan. In addition to administrative records, this database included laboratory results for some patients. We searched for individuals aged ≤ 18 years with a diagnosis of KD (International Statistical Classification of Diseases and Related Health Problems, 10th revision, code M30.3) who had received high-dose (≥ 1 g/kg) IVIG therapy. The primary outcome measure was post-IVIG therapy Hb dynamics in patients for whom laboratory findings were available. Secondary outcomes included the proportion of patients whose Hb value decreased below a specified threshold (e.g., 1 g/dL) and the number who received red blood cell transfusions, identified by a Japanese administrative code, in the whole cohort.

RESULTS: Laboratory data were available for 979 of 8262 patients with KD receiving high-dose IVIG. Hb dynamics assessed on spline curves showed that mild anemia commonly occurred 1-2 days after IVIG infusion and returned to the baseline thereafter. Declines of Hb > 1 g/dL and > 2 g/dL were found in 21.8% and 4.3% of patients, respectively. Two of the 8262 individuals with KD had received transfusions after IVIG therapy (incidence rate 0.024%; 95% confidence interval 0.003-0.087), but the indication for transfusion could not be determined from our records.

CONCLUSIONS: Although mild anemia commonly occurred post-IVIG therapy in Japanese individuals with KD, severe anemia necessitating transfusion was rare in these patients.