Genetic Carrier Screening

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	Most common genetic cause of mortality in children under two
Carrier Risk	1 in 25	1 in 150	1 in 40
People with the condition	1 in 2,500	1 in 4,000 males 1 in 8,000 females	1 in 6–10,000
Testing approach	Next Generation Sequence Testing for the 2,000 CFTR variants that are associated with more than 99.9% of CF cases	Testing for triplet repeat expansions in the FMR1 gene that are associated with more than 99% of FXS cases. Reflex AGG interrupt testing for women with a premutation in the range of 55 - 69 repeats	SMN1 gene deletion testing, accounting for 96% of disease-causing variants
Inheritance	Autosomal recessive; both parents must be carrier to have an affected child	X-linked; the mother must be a carrier to have an affected child	Autosomal recessive; both parents must be 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:

>99.9% of cystic fibrosis carriers
>99% of fragile X carriers
>95% of spinal muscular atrophy carriers

Our carrier screening now includes massively parallel sequencing (NGS) to improve identification of CF carriers, and AGG interrupt analysis to provide a more precise estimate of the chance of a premutation expanding to a full mutation in the next generation, which will help to better inform reproductive choices for FXS 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 because some very rare genetic variants cannot be detected by the test.

How to get tested

Step 1

Patient Discussion

Talk to your patient about their reproductive carrier screening options, and request a Genetic Carrier Screening test.

Step 2

Sample collection

Have your patient visit one of our collection centres to get their sample collected.

Step 3

Test results

Discuss the results with your patient and advise genetic counselling if necessary.

Frequently asked questions