Objective Compare trends in coronary artery (CA) abnormality diagnoses to trends in adverse cardiac outcomes among American children with Kawasaki disease (KD) to assess the fit of detection of CA abnormalities to an established model of overdiagnosis.

Design Multicenter retrospective cohort.

Setting 48 US children’s hospitals in the Paediatric Health Information System database.

Participants Children <18 years receiving care for KD between 2000 and 2014.

Main outcome measures The main outcomes were rates of CA abnormality diagnoses and adverse cardiac outcomes, measured during a child’s incident KD visit and longitudinally at all subsequent visits to the same hospital, through December 2016. CA abnormalities were considered severe if long-term anticoagulation other than aspirin was prescribed. Trends were tested using mixed effects logistic regression, adjusting for patient demographics.

Results Among 17 809 children treated for KD, a CA abnormality was diagnosed in 1435 children (8%), including 1117 considered non-severe and 318 severe. The rate of non-severe CA abnormality diagnoses increased from 45 per 1000 patients with KD in 2000 to 81 per 1000 patients with KD in 2014, representing an adjusted 2.3-fold increased odds (95% CI 1.8 to 3.0) of diagnosis. There was no significant change in diagnoses of severe CA abnormalities. Adverse cardiac outcomes were stable over the study period at 19 per 1000 patients with KD (P=0.24 for trend).

Conclusions The rising rate of detection of non-severe CA abnormalities accompanied by an unchanging rate of adverse cardiac outcomes among American children with KD fits an overdiagnosis pattern.