Cystic Fibrosis (CF) is a multisystem disorder caused by mutations in the gene for the CF transmembrane conductance regulator (CFTR), which encodes an ion channel protein, with more than 2000 mutations identified to date. A diagnosis of CF initially relied on phenotype, with clinical recognition of characteristic signs and symptoms.
Diagnostic Criteria for Cystic Fibrosis
BOTH of the following criteria must be met to diagnose cystic fibrosis (CF):
- Clinical symptoms consistent with CF in at least one organ system, or positive newborn screen or genetic testing for siblings of patients with CF
- Evidence of cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction (any of the following):
- Elevated sweat chloride ≥60 mmol/L
- Presence of two disease-causing variants in CFTR, one from each parental allele
- Abnormal nasal potential difference
The accuracy of sweat chloride and nasal potential difference measurements are operator-dependent, so it is critical that testing be performed in experienced centers, following standard guidelines.
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Created Feb 27, 2020.