Algorithm for the diagnosis of cystic fibrosis

CF: cystic fibrosis; IRT: immunoreactive trypsinogen; DNA: genetic screen for pathogenic CF transmembrane conductance regulator (CFTR) gene variants.
* For asymptomatic infants with intermediate sweat chloride results, sweat chloride testing should be repeated at 1 to 2 months of age.
¶ For infants with sweat chloride ≥60 mmol/L, CFTR sequencing is not mandatory if the newborn screen included DNA testing and definitively identified 2 CF-causing variants.
Δ "CF-causing variants" denotes variants in the CFTR gene that are known to cause disease, using classifications identified in the CFTR2 project.