Background/Aims: Cystic fibrosis (CF) in infancy and childhood is often associated with failure to thrive (FTT). This would suggest that in countries without a newborn screening program for CF, FTT could be used as a clinical screening tool. The aim of this study is to assess the diagnostic performance of FTT for identifying children with CF. Methods: Longitudinal length and weight measurements up to 2.5 years of age were used from CF patients (n= 123) and a reference group (n= 2,151) in The Netherlands. Growth …