Clinical and Laboratory Findings in Children with Positive Newborn Screening for Cystic Fibrosis: A Multicenter Retrospective Study

Aim: In some settings, the diagnostic evaluation of cystic fibrosis (CF) may be delayed due to limited access to sweat chloride tests.This study aimed to describe the clinical and laboratory findings observed during the evaluation of children with positive newborn screening (NBS) results for CF.Materials and Methods: We retrospectively reviewed the data of children referred after positive NBS for CF who were evaluated at three pediatric pulmonology centers between 2015 and 2021.NBS was used as a referral tool, and the diagnosis of CF was established according to standard diagnostic criteria, including the sweat chloride test and/or genetic analysis.Demographic characteristics, clinical features, and laboratory findings were compared between those children diagnosed with CF after NBS and those not diagnosed with CF.Results: A total of 1,469 children were included, of whom 76 (5.2%) were diagnosed with CF.CF was more frequently observed in those children with parental consanguinity, a history of meconium ileus, steatorrhea, doll-like facial appearance, metabolic alkalosis, hyponatremia, hypokalemia, hypochloremia, and having a sibling with CF (all p<0.05). Conclusion:This large multicenter cohort study presents real-life data on the clinical and laboratory findings observed in those children with positive NBS for CF.This study does not propose an alternative diagnostic strategy to the sweat chloride test, but highlights supportive clinical features which may raise clinical suspicion and emphasizes the importance of timely referral and follow-up, particularly in settings where access to confirmatory testing may be delayed.