New predictors to identify severe cases during intravenous immunoglobulin therapy in Kawasaki disease.

Background: The purpose of this study was to predict which patients would require plasma exchange therapy (PEX) using laboratory findings during intravenous immunoglobulin (IVIG) therapy in Kawasaki disease.

Methods: A retrospective, single-center, cohort study was conducted. Of the 621 IVIG-treated patients, 166 patients who received a second IVIG dose on the second day after initiation of IVIG were included. The endpoint was PEX. Participants were divided into two groups: 10 patients who received PEX and 156 patients who did not. The variables were C-reactive protein (CRP), white blood cell count (WBC), and neutrophil fraction (NEUT) at three time points: pre-initial IVIG, pre-second IVIG, and post-second IVIG. The change ratio (post-IVIG value/pre-IVIG value) of each variable, with each IVIG dose, was calculated. Receiver operating characteristic analysis determined the area under the curve (AUC) and cut-off values.

Results: The variables with an AUC > 0.9 were CRP (post-second IVIG), change ratio of CRP (CRP value post-second IVIG/CRP value pre-second IVIG), NEUT (pre-second IVIG), and NEUT (post-second IVIG). Among these, the variables with high sensitivity were CRP (post-second IVIG) and the change ratio of CRP (second IVIG), with cut-off values of 9.52 mg/dL and 0.99, respectively. The sensitivity and specificity of these variables were 100% and 91%, and 100% and 80%, respectively. The combined sensitivity and specificity (95% confidence intervals) of these two variables were 100% (59-100) and 94% (89-97).

Conclusion: High CRP levels and the change ratio of CRP after the second IVIG dose were associated with PEX.