Genetic Testing
GENETIC TESTING
Cystic fibrosis (CF) came into the human genome about 5,000 years ago and it has survived and spread. Today there are more than 2,000 mutations that lead to CF, some of which are particular to individual families. At the other extreme, one mutation, Delta F508, is present in some 72% of all cases worldwide.
Carriers are symptomless and live normal lives. They are overwhelmingly unaware of their CF carrier status. Yet they have every chance of passing on the gene to the next generation and that generation to the next and so on – it is only a matter of time before a member of the family is born with CF. If both parents are carriers of the CF gene change, then there is a 25% risk of that child having CF with each pregnancy. Being a CF carrier does not mean you have CF; carriers usually display no symptoms of CF. In Australia, it is estimated that 1 in 25 people carry the CF gene, but are unaware.
Thinking about having children? Then first we implore you to think carrier screening.
What is a Carrier Screening?
Carrier screening services are available in Australia. This screening helps people find out whether they have a chance of having a child with a genetic condition. CF carrier screening is available to those 18 years and over and is the only way to find out if you are a carrier of the CF gene change.
There are several different screening options are available:
• A 3-panel screen, which screens for carriers of three of the most common inherited conditions:
– cystic fibrosis (CF)
– spinal muscular atrophy (SMA)
– fragile X syndrome (FXS).
• A single panel screen, which screens for carriers of one of these conditions.
• A larger panel, which screens for carriers of a wider range of common and rare inherited conditions.
People with a family history of a particular genetic condition may wish to request testing for that specific condition only, or they may wish to request a test that also includes other commonly inherited conditions.
If you have a family history of CF, it is important to tell your GP, obstetrician or gynaecologist before providing your sample for screening. This will ensure that you are being tested for the most common CF gene changes as well as the specific gene change relevant to your family. However, there is still a small risk that you may be a carrier of a rare CF gene change.
For people with a close relative who has CF, the cost of the test may be covered by Medicare. Speak to your doctor to check your eligibility for the rebate. If you have no family history of CF, you can pay for the test yourself (the cost will vary depending on the test, but expect to pay at least $150).
If you decide to be tested
Carrier screening not only plays a key role in the diagnosis of cystic fibrosis, but testing also allows parents to find out what their chances are of having a child with CF to help inform important family planning decisions. Everyone’s reason for wanting or not wanting to know their CF carrier status will be different. What is important is that you feel you have made an informed choice that suits your particular situation and needs.
If you decide to be tested:
1. Visit your healthcare provider
Genetic carrier screening is usually requested by general practitioners, obstetricians, fertility specialists, midwives, genetic counsellors or medical geneticists. Let your healthcare provider know that you wish to have genetic carrier screening.
Your healthcare provider will need to complete a test request form that you can take to a local pathology collection centre. Alternatively, if you do not live near a pathology collection centre you can order a saliva sample kit that can be mailed to you.
It is recommended that your testing be performed by a specialist genetic testing laboratory
2. Take the test
It is recommended that the female partner is tested first, as testing may include conditions carried on the X chromosome.
Take your test request form to an affiliated pathology collection centre and have your blood or saliva sample taken.
If you have a family history of some conditions, such as CF, Medicare and Private health insurance may subsidise the cost of carrier screening.
3. Visit your healthcare provider to get your results
Typically your results will be communicated to your healthcare provider within 2-4 weeks. They will inform you if you carry a gene change for any of these conditions.
4. If the test shows you are a carrier
It is recommended that you discuss your result with a genetic counsellor.
Some carrier screening services provide genetic counselling as part of their service.
Depending on your result, your healthcare provider or a genetic counsellor will discuss carrier testing for your partner.