Carrier screening is genetic testing performed to determine whether individuals or couples have a genetic variant
(mutation) that may affect their chance of having a child with a genetic condition. The Genomic Diagnostics Genetic Carrier Screen tests for three relatively common genetic conditions in general populations: Cystic Fibrosis (CF), Fragile X (FXS), and Spinal Muscular Atrophy (SMA). These conditions were chosen based on their inclusion in local and international genetic screening recommendations for patients considering conception(1,3).
Many children affected by these conditions are born to families with no history of disease due to the relatively rare nature of the conditions and inheritance patterns – autosomal recessive or X-linked in the included conditions. The value of carrier screening for CF and SMA has therefore been recognised for all patients in some countries such as the United States(1), with the value of Fragile X also being recently recognised in Australian research(2).
Importantly, if couples are found to be carriers of these conditions, they can consider several reproductive options including:
- natural pregnancy, with or without prenatal diagnosis
- preimplantation genetic diagnosis (PGD) with in vitro fertilization (IVF) to test and then transfer embryos that are free of the condition
- the use of a sperm or egg donor
When should patients be tested?
The ideal setting for carrier screening is preconception, in order to have the most time to deal with all possible testing outcomes. However, testing can also be used in an antenatal setting.
If the couple are shown to be carriers for any of these conditions, then genetic counselling is recommended so that they can get more information and discuss in detail their options and potential impacts of their situation.
How can I get my patient tested?
The recommended testing pathway is to initially test the female partner, and to only test her partner if she is found to be a carrier.
This test is not covered by Medicare and is $385. Partner testing is available by simply requesting CF and SMA screening at a combined cost of $385.
- ACOG Committee Opinion, No. 690, March 2017. “Carrier Screening in the Age of Genomic Medicine”.
- Metcalfe, S.A. Genetics In Medicine, 2017. “Informed decision making and psychosocial outcomes in pregnant and non-pregnant women offered population fragile X carrier screening”.
- Prenatal screening and diagnosis of chromosomal and genetic abnormalities in the fetus in Pregnancy. RANZCOG. C-obs 59.