Commonly performed genetic testing (explain results only) - cystic fibrosis mutation testing

Role

Genetic testing for CFTR gene mutations confirms the diagnosis of cystic fibrosis, characterises the specific variant(s) present, and increasingly determines eligibility for CFTR modulator therapy, which is mutation-specific
Over 2,000 CFTR variants have been described; F508del is the most common pathogenic variant globally, though variant frequency differs by population/ethnicity

CFTR variants are classified by functional consequence (Class I-VI, spanning no protein production through to reduced protein stability/function) - this functional classification, not just the presence of a variant, determines which modulator therapies (if any) are likely to be effective for a given genotype

Diagnosis combines sweat chloride testing (the primary diagnostic test - elevated chloride reflects defective CFTR-mediated chloride transport) with genetic testing, which is used to confirm the diagnosis, identify carrier status in relatives, and specifically to determine CFTR modulator eligibility
Newborn screening (immunoreactive trypsinogen, followed by CFTR mutation panel testing) enables early diagnosis before symptoms develop in many countries, including Australia

CFTR modulator therapy (e.g. ivacaftor, lumacaftor/ivacaftor, elexacaftor/tezacaftor/ivacaftor combinations) is prescribed based on the specific CFTR genotype, not the diagnosis of CF alone - genetic testing is therefore directly therapy-determining, not just diagnostic, representing a shift toward genotype-directed precision therapy in CF care
The move to genotype-directed modulator therapy means CFTR mutation testing has become progressively more clinically consequential over time - a full genotype (not just confirmation of "a" CFTR mutation) is now essential information for treatment planning

Pancreatic insufficiency, CF-related diabetes, CFTR modulator therapy eligibility, carrier screening in reproductive partners of known carriers

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