Genetic Carrier Screening | Genomic Diagnostics

What is the genetic carrier screening?

Genetic Carrier Screening is a DNA test that helps identify individuals or couples who may be at increased risk of having a child with a serious inherited genetic disorder. This information can support informed reproductive decisions. While more than one in 20 Australians is a carrier of at least one genetic condition, most have no family history of the disorder. This is because these conditions are often rare and follow specific inheritance patterns, such as autosomal recessive or X-linked.

Genetic Carrier Screening (GCS) is particularly useful for detecting the three most common inherited genetic disorders in Australia:

Cystic Fibrosis (CF)
Spinal Muscular Atrophy (SMA)
Fragile X Syndrome (FXS)

Carriers of these conditions typically do not experience symptoms themselves, but they do face an increased chance of passing the disorder on to their children. Testing can help you better understand your risk and guide your reproductive choices.

How does the test work?

Our expert Genomic Diagnostics team will use the DNA from your blood sample to test for the most common inherited genetic changes that cause cystic fibrosis, spinal muscular atrophy and fragile X syndrome.

Genetic testing is the only way to find out whether or not you are a carrier for one of these conditions.

Knowing your carrier status can help you make informed choices. For many people, genetic carrier screening provides peace of mind. For those with a higher risk of having an affected child, it provides the opportunity to consider a range of reproductive options.

About the genetic conditions screened

Cystic fibrosis, spinal muscular atrophy and fragile X syndrome can have devastating effects on life-expectancy and quality of life.

Cystic fibrosis is the most common inherited disorder in Caucasians.
Spinal muscular atrophy is the most common genetic cause of mortality in children under two.
Fragile X syndrome is the most common form of inherited intellectual disability.

We provide genetic counselling free of charge for carrier couples when at least one partner has their test at one of our Healius Pathology network collection centres.

Cystic fibrosis and spinal muscular atrophy are autosomal recessive conditions, which means both parents must be carriers to have an affected child. Fragile X syndrome is an X-linked condition, so only the mother must be a carrier to have an affected child.

Hear from a genetic counsellor

If you and your reproductive partner are found to be a carrier couple for any of these conditions, you have the option of being referred by your clinician to a genetic counsellor to discuss your reproductive options, including:

natural pregnancy, with or without prenatal diagnosis
pre-implantation genetic diagnosis (PGD) with in vitro fertilisation (IVF) to test and then transfer embryos that are free of the condition
the use of a sperm or egg donor
adoption

Patients' process

Step 1

Get a doctor's request

Your doctor will discuss genetic carrier screening with you and complete a request form.

Step 2

Have a blood test

Visit your local Healius Pathology collection centre to have your blood sample taken.

Step 3

Get your results

Your genetic carrier screen results will be delivered to your doctor within 10 – 14 days*.

If you and your partner are identified as a carrier couple, we will offer free genetic counselling to support you with your next steps.

*from when it reaches the laboratory

FAQ

Resources

Genetic carrier screen patient brochure

Download

Genetic carrier screen request form

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Order your test

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Why recommend screening to your patients?

Genetic carrier screening helps to inform reproductive decision-making and gives carrier couples (where both partners are carriers for CF or SMA or the female partner is a carrier for FXS) the opportunity to consider a range of reproductive options.

Due to the recessive nature of these conditions, 88% of carriers have no family history.¹

When to offer screening

RANZCOG recommends that information on carrier screening be offered to all women planning a pregnancy or in the first trimester of pregnancy.² This includes screening for CF, FXS and SMA. The genetic carrier screening test can be easily added as part of a patient’s routine antenatal blood screening.

There is global consensus that genetic carrier screening is best performed before pregnancy. This gives your patients the widest range of reproductive choices and more time to make important decisions.

Carrier screening can still be offered in early pregnancy, although options will be more limited and time-sensitive.

The recommended screening pathway is to test the female partner first, followed by the male partner if the female is identified as a carrier for CF or SMA.

Genetic conditions screened

CF, SMA and FXS can have devastating effects on life-expectancy and quality of life. The combined affected pregnancy rate for these disorders is equivalent to the population risk of having a child with Down syndrome.

Cystic Fibrosis	Fragile X Syndrome	Spinal Muscular Atrophy
Description	Most common inherited disorder in Caucasians	Most common form of inherited intellectual disability
Carrier Risk	1 in 25	1 in 200
People with the Condition	1 in 2,500	1 in 3,600 males 1 in 6,000 females
Testing Approach	Testing for the 50 most common CFTR variants that are associated with more than 95% of CF cases	Testing for triplet repeat expansions in the FMR1 gene that are associated with more than 99% of FXS cases
Inheritance	Autosomal recessive; both parents must be carriers to have an affected child	X-linked; the mother must be a carrier to have an affected child

Accuracy of screening results

Genetic carrier screening tests for the most common genetic changes associated with CF, SMA and FXS.

The assay can detect:

>95% of cystic fibrosis carriers
>99% of fragile X carriers
>95% of spinal muscular atrophy carriers

The tests used for GCS are highly accurate diagnostic tests that reliably identify carriers for these conditions. However, genetic carrier screening cannot identify a small percentage of carriers (1-5%) because some very rare genetic variants cannot be detected by the test.

References