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The commonly used newborn screening tests will identify 85–90% of individuals with cystic fibrosis (CF), but will not identify individuals with rare (atypical) CF variants. 1 Such patients may present to the general practitioner (GP).
What do I need to know?
CF is the most common life threatening genetic condition in Australia. CF primarily affects the lungs and digestive system, which become obstructed with excessive, thick mucus. It is a condition that follows an autosomal recessive inheritance pattern, meaning both parents must carry a CF-causing gene variants to be at risk of having a child with the disease.
About one in 25 Australians of northern European ancestry are carrierof the CFTR gene variant. The most common variant in the CFTR gene is the ΔF508 variant, which accounts for approximately 70% of all CFTR gene variant in those of northern European ancestry. While there are more than 2000 variants in the CFTR gene, around 40 variants contribute to approximately 90% of cases of CF in Australia.1,2
Almost all babies in Australia are screened at birth for CF. There are some who may be lost to follow up or refuse to consent for screening. Exact numbers in Australia are not available. Refer to ‘Newborn screening’ for more information.
Carrier screening for CF can be offered by GPs to all couples planning a pregnancy (or already pregnant), regardless of family history or ethnicity. Refer to ‘Reproductive carrier screening’ for more information.
Carrier screening for CF is also available through some genetic screening programs for at-risk groups (eg people of Ashkenazi Jewish ancestry) and through commercial carrier screening tests.1
When should I refer?
Couples who are CF carriers should be referred for genetic counselling if they are planning a pregnancy or in the first trimester of pregnancy.3
Children suspected of having CF (who have not been previously identified through newborn screening tests) should be referred to a paediatrician for a sweat test. Symptoms may include recurrent cough, failure to thrive, lower respiratory tract infection, bronchiectasis and/or rectal prolapse.
Males presenting with infertility due to congenital bilateral absence of the vas deferens (CBAVD) may have an atypical form of CF. Refer the patient to a fertility specialist.4
Cascade screening should be offered following a diagnosis of CF in the family to identify other potential carriers.1
Resources for patients
National Library of Medicine, Cystic fibrosis
Better Health Channel, Cystic fibrosis
Centre for Genetics Education, Fact sheet 41: Cystic fibrosis
Cystic Fibrosis Australia