From lip to lab: salty tasting skin is the main clue that raises clinical suspicion of cystic fibrosis in young infants.

Aim: This study developed a clinical decision rule (CDR) to rule in or rule out cystic fibrosis (CF) in the first weeks of life.

Methods: We combined a two-step nonconcurrent birth cohort and a cross-sectional controlled study in which observers and mothers were blinded to confirmatory sweat test results. Neonates from uncomplicated pregnancies and deliveries, with two subsequent tests for immunoreactive trypsinogen (IRT) higher than 70 ng/mL, were eligible to take part.