Relationship between post-IVIG IgG levels and clinical outcomes in Kawasaki disease patients: new insight into the mechanism of action of IVIG.

Abstract

The dosing of intravenous immunoglobulin (IVIG) therapy for Kawasaki disease (KD) has been a matter of debate for decades, with recent studies implicating that larger doses lead to better outcomes. Despite this, few have investigated post-IVIG infusion immunoglobulin G (IgG) levels in relation to outcomes of KD such as response to IVIG and development of coronary artery abnormalities (CAAs). The present study investigated how varying levels of post-infusion IgG affected these outcomes. We collected demographic and laboratory data, including post-infusion IgG, from children with KD who were admitted to six hospitals in Japan between 2006 and 2012. We conducted multivariate analyses to examine the relationship between independent variables and non-response to IVIG and development of CAAs. We used random forest, a decision tree-based machine learning tool, to investigate the marginal effect of varying post-infusion IgG levels on non-response to IVIG and development of CAAs. Of 456 patients included in the study, 130 (28.5%) were non-responders and 38 (8.3%) developed CAAs. Sodium, post-infusion IgG, and AST were significantly associated with non-response. Post-infusion IgG and sodium were significantly associated with CAA development. The random forest plots revealed a decrease in non-response and CAA rates with increasing post-infusion IgG until post-infusion IgG was near the median (2821mg/dL), after which the non-response and CAA rates leveled off. Greater post-infusion IgG is associated with better response to IVIG and decreased CAA development in KD patients, but this effect levels off at post-infusion IgG levels greater than the median. Key points • Though previous studies have shown that post-intravenous immunoglobulin (IVIG) infusion immunoglobulin G (IgG) is associated with non-response to IVIG therapy and coronary artery abnormality (CAA) development in Kawasaki disease (KD) patients, no study has investigated the relationship between varying levels of post-infusion IgG and these clinical outcomes. • Our study showed that non-response to IVIG therapy and CAA development in Kawasaki disease patients follow a decreasing trend with increasing post-infusion IgG at post-infusion IgG levels below the median. • At values of post-infusion IgG greater than the median, non-response and CAA development rates remain relatively constant with increasing post-infusion IgG. • Our study suggests that when post-infusion IgG is greater than the median, IgG may have fully bound to the therapeutic targets of KD, and in these patients, there may be limited benefit in administering additional IVIG.