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Complexities of genetic carrier screening in focus
With MBS access to screening starting soon for those who are pregnant or planning pregnancy, newsGP looks at the likely impact on GPs.
Upcoming changes to the MBS are expected to generate more interest in reproductive carrier screening testing.
From November 1, MBS changes are expected to come into effect that will allow individuals who are pregnant or planning pregnancy, along with their reproductive partners, to freely access three-condition reproductive carrier screening.
The screening test will cover three genetic conditions that are relatively common: cystic fibrosis (CF), spinal muscular atrophy (SMA) and fragile X syndrome (FXS).
Research suggests about one in 20 Australians are genetic carriers of at least one of these conditions, although most carriers will not have a family history of the disorders. Approximately one in 240 couples will both be carriers, meaning they have a one in four chance of having a child who is affected by CF, SMA or FXS.
It is expected the funding will increase demand for carrier screening, which is currently available at a cost of around $400 per person.
Additionally, GPs are likely to encounter more patients who are interested in pursuing testing and will need to be prepared for giving advice, arranging testing and discussing the implications of results.
‘One of the really important things is once you remove a cost barrier, you will have more couples or women interested in seeking this information,’ Dr Wendy Burton, Chair of RACGP Specific Interests Antenatal and Postnatal Care, told newsGP.
Dr Burton, who was involved in Mackenzie’s Mission, a large research project that offered reproductive carrier screening to thousands of couples across Australia, said this was reflected in her professional experience. She emphasised the importance of understanding the testing implications when discussing screening options with patients who may be more inclined to consider testing after the MBS changes come into effect.
‘It is really important that GPs understand what the testing involves, what it does tell us and what it does not tell us, and what you do with what you find,’ she said.
Dr Burton highlighted the complex nature of providing information to enable informed choices.
‘If you were to do a decision tree, it would be enormous,’ she said.
The Royal Australian and New Zealand College of Obstetricians and Gynaecologists recommends that reproductive carrier screening be offered to all women who are pregnant or planning pregnancy, including three-condition testing or expanded panels. The latter, which will not be funded under the upcoming MBS changes, may include hundreds of genetic disorders.
There are two options when referring for reproductive carrier screening – sequential or couple testing. Sequential testing is generally preferred and involves testing women who are planning pregnancy. Once their result is available, a decision is made on whether their partner also requires testing. It is unclear whether there will be additional funding to allow affected individuals and couples to access IVF and pre-implantation genetic testing.
The alternative approach is couple testing, where pregnant individuals and their reproductive partner are tested simultaneously. This is the preferred option when pregnancy has been confirmed as it prevents delays in risk assessment, genetic counselling and diagnostic testing if required.
There are a number of options for couples who are not yet pregnant and are found to have a high chance of having an affected child. These include:
- conceiving naturally and having the baby tested after birth
- conceiving naturally and having diagnostic testing during pregnancy, with the option to consider a termination if the baby is found to be affected
- undergoing IVF and pre-implantation genetic testing in order to select unaffected embryos
- undergoing IVF using donor gametes who are not carriers of the condition
- adoption
- not having children.
For affected couples who are already pregnant, it is recommended to refer immediately to a maternal-foetal medicine unit and a genetic counsellor, with some pathology providers offering free counselling services.
Dr Burton advises that the potential psychological impacts and financial costs associated with these options must be addressed when having conversations with patients who are considering reproductive carrier screening.
‘If a couple finds that they are a carrier for [SMA] and say it’s a variant for which there isn’t much in the way of treatment available at the moment, then do they have to take their chances? Ultimately, they could, of course, have chorionic villus sampling or amniocentesis, get a diagnosis at that point and terminate, but that’s a very different process to a preimplantation diagnosis and a decision not to implant,’ she said.
‘These are important conversations, because there are individuals who would feel completely conflicted about terminating a pregnancy who might not have that same conflict about not implanting an affected embryo.’
Dr Burton also stressed the importance of the language used to have these conversations and the broader social and ethical implications of carrier screening.
‘If we as a society have this testing, what does that say about what we think about people living with these conditions and their families who love and care for them?’ she said.
‘What does this say about the value our society places on individuals who, for example, have [CF] or any of these conditions?
‘I’m not standing in judgement in any way, shape or form of anybody. These are complex decisions.’
Dr Burton recommends GPs utilise resources from genetic pathology providers, such as
Victorian Clinical Genetics Services, who deliver online learning modules, and to look out for clinical practice guideline updates following the MBS changes.
Reproductive carrier screening remains an optional rather than a routine test as individuals must make an informed choice on whether to undergo testing. The RACGP’s
Genomics in general practice advises ‘the decision to undertake carrier screening is a personal choice to be made by the individual/couple’.
More details and resources for reproductive carrier screening are available on the RACGP website.
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