Population-based genetic carrier screening for cystic fibrosis in Victoria

To the Editor: Cystic fibrosis (CF) is the most common inherited life-shortening condition affecting Australian children, with a carrier frequency of 1 in 25. Most children with CF (94%) have no family history of the condition.1 The Human Genetics Society of Australasia recommends that couples planning or in the early stages of pregnancy be made aware of the availability of CF carrier screening.2 In Victoria, since 2006, CF carrier screening has been available to individuals and couples as a fee-for-service program.3 The program initially screened for 12 mutations (2006–2012) and now screens for 38 mutations (2012–2013) at a cost of $150 per patient. The program was established through collaboration between Victorian Clinical Genetics Services, the CF clinic at the Royal Children’s Hospital in Melbourne, obstetricians and Cystic Fibrosis Victoria.

Over the past 7 years, the program has screened 10 489 individuals with no family history of CF, with 320 (3.05%; 1 in 33) found to be CF carriers. Of these, 267 (83.4%) were carriers of the common mutation p.F508del. Fifteen carrier couples were identified (four couples with non-p.F508del mutations). Eleven carrier couples were pregnant at the time of screening and nine had prenatal diagnosis (three affected, four carrier and two non-carrier fetuses). All three couples with affected pregnancies chose termination. All carrier couples who had subsequent pregnancies chose prenatal diagnosis or preimplantation genetic diagnosis. Only one child with CF has been born to a mother who screened as low risk. The child had paternal uniparental disomy for a CFTR mutation, an extremely rare cause of CF that cannot be predicted by screening of parents.

We have demonstrated that carrier screening for CF can be undertaken successfully before or in the early stages of pregnancy. The use of preimplantation genetic diagnosis for subsequent pregnancies emphasises the need to offer carrier screening before pregnancy, when more reproductive options are available.

Although it is not possible to ascertain the uptake of testing, significant barriers include cost and lack of knowledge and awareness.4 Government funding of CF carrier screening is essential in making screening broadly accessible. Professional and community education will be instrumental in raising awareness about the availability of carrier screening, particularly given that advances in genetic testing mean that carrier screening panels for multiple genetic conditions are now available.