Higher IVIG resistance in Kawasaki disease patients treated early after fever onset: a single-center retrospective study of 2,988 cases.

To investigate the impact of intravenous immunoglobulin (IVIG) timing on coronary artery outcomes and treatment response in children with Kawasaki disease (KD). This retrospective study analyzed 2,988 pediatric patients with Kawasaki disease (KD) who received initial IVIG treatment within 3-7 days of fever onset. Patients were categorized by IVIG initiation time: Group A (day 3 of fever, n = 134), Group B (day 4 of fever, n = 465), Group C (day 5 of fever, n = 1101), Group D (day 6 of fever, n = 833), and Group E (day 7 of fever, n = 455). We compared baseline characteristics, IVIG resistance, and convalescent-phase coronary artery lesions (CALs). Multivariate logistic regression analyzed the association between early initiation (days 3-4 of fever) of initial IVIG therapy and IVIG resistance or convalescent-phase CALs. Propensity score matching (PSM) was used to match the early (days 3-4 of fever, n = 590) and conventional (days 5-7 of fever, n = 590) treatment groups. Baseline data during the acute phase revealed that with delayed initiation of initial IVIG treatment, serum albumin (ALB), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) levels in children with KD showed a significant overall decreasing trend (P < 0.001), while platelet (PLT) counts and the incidence of acute-phase CALs showed a significant overall increase (P < 0.001). However, no significant difference was found in convalescent-phase CALs incidence among groups. IVIG resistance was more common among children who required early treatment (P < 0.001). PSM analysis showed no significant difference in acute or convalescent-phase CALs between the early and conventional groups. In the multivariate logistic regression analysis after adjusting for confounders, early IVIG initiation was not significantly associated with convalescent-phase CALs but was associated with a significantly increased risk of IVIG resistance (OR: 1.74; 95% CI: 1.32-2.29; P < 0.001).Conclusion: In this single-center retrospective study, initiating initial IVIG therapy within 3-7 days of fever onset showed no significant impact on the incidence of convalescent-phase CALs at different treatment timings. However, IVIG resistance was more common among children who required early treatment (days 3-4 of fever). Due to potential residual confounding by indication, these findings represent a non-causal association that may reflect differences in underlying disease severity and clinical presentation. Future prospective, multicenter, randomized controlled trials are needed to further clarify the optimal timing of initial IVIG therapy in KD patients, thereby providing evidence for developing individualized treatment strategies and improving long-term prognosis.