Newborn screening will identify 85–90% of individuals with cystic fibrosis (CF), but will not identify individuals homozygous/compound heterozygous for rare CFTR (cystic fibrosis transmembrane conductance regulator) variants. Such patients may present to the general practitioner symptomatically (GP) symptomatically.
What do I need to know?
CF is the most common childhood onset 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 pattern, meaning both parents must carry a CF-causing to be at risk of having a child with the disease.
About one in 25 Australians of northern European ancestry are of a CFTR pathogenic variant. The most common variant in the CFTR gene is the p.Phe508del variant, which accounts for approximately 70% of all CFTR pathogenic variants in those of northern European ancestry. While there are more than 2000 variants in the CFTR gene, most of which are benign or of uncertain significance, around 40 pathogenic variants cause approximately 90% of CF in Australia.
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.
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.
When should I refer?
Couples who are CF carriers should be referred for genetic counselling if they are planning a pregnancy or are in the first trimester of pregnancy.
Children suspected of having CF (who have not been previously identified through newborn screening tests) should be referred to a respiratory paediatrician for a sweat test. Symptoms may include recurrent cough, failure to thrive, lower respiratory tract infections, 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. These men should be referred to a fertility specialist.
should be offered following a diagnosis of CF or of a CFTR pathogenic variant carrier in a family to identify other carriers.
- RANZCOG policy on Genetic Carrier Screening
- Australasian Guideline (2nd Edition): an Annex to the CLSI and UK Guidelines for the Performance of the Sweat Test for the Diagnosis of Cystic Fibrosis *John Massie, Ronda Greaves, Michael Metz, Veronica Wiley, Peter Graham, Samantha Shepherd, Richard Mackay. Clin Biochem Rev 38 (3) 2017
- The Royal Australian College of General Guidelines for preventive activities in general practice. 9th edn. Melbourne: RACGP, 2016. [Accessed 6 September 2022].
- Kessels SJM, Carter D, Ellery B, et al. Prenatal genetic testing for cystic fibrosis: a systematic review of clinical effectiveness and an ethics review. Genet Med. 2020 Feb;22(2):258-267.
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