Implications of Changing Z -Score Models for Coronary Artery Dimensions in Kawasaki Disease

Background Coronary artery abnormalities in Kawasaki disease (KD) are assessed using echocardiographic z -scores. We hypothesized that changing the coronary artery (CA) z -score model would alter diagnosis and management of children with KD. Methods In this retrospective single-center study of children treated for KD (9/2007–1/2020), we collected echocardiographic measurements for the left anterior descending (LAD), right (RCA), and left main (LMCA) coronary arteries during 3 illness phases and calculated Boston and Pediatric Heart Network (PHN) z -scores. Agreement between Boston and PHN z -scores was assessed using Kappa ( κ ) and Lin’s Concordance Correlation Coefficients (CCC) and Bland–Altman analysis. Results For 904 echocardiograms from 357 children, the median Boston LAD z -score was lower than the PHN (0.3 [IQR − 0.6, 1.5] vs 1.6 [IQR 0.7, 2.8], CCC 0.94 [95% CI 0.93, 0.95], moderate agreement), aggregated across all illness phases. RCA and LMCA z -scores showed substantial agreement. With conversion from Boston to PHN models, the percentage of individual LAD z -scores ≥ 2.5 increased (14.6% to 32.1%). At least one CA z -score classification changed in 213 children (59.7%) across all phases, and 48 children (13.4%) had a change that altered recommended antithrombotic strategy. Agreement between models differed by age, sex, and race. Conclusions Conversion from Boston to PHN z -scores changed at least 1 CA z -score classification in over half of KD patients and changed recommended antithrombotic management in 13%, largely driven by LAD measurements. Since diagnosis and management of KD and KD-like diseases rely upon CA z -scores, the clinical and research implications of these findings merit further exploration.