Blueprint for screening trial revealed: what would-be parents need to know

Jonathan and Rachael Casella hold their baby daughter Mackenzie who was diagnosed with SMA and died one year ago.
Jonathan and Rachael Casella hold their baby daughter Mackenzie who was diagnosed with SMA and died one year ago. Photo: Supplied

The researchers planning to screen thousands of couples for 500 severe genetic conditions they risk passing onto their children have officially launched the landmark trial that could transform how Australians plan to start their families.

The first detailed blueprint for the Mackenzie’s Mission carrier screening trial was released this month, revealing how the three-year trial will work and what the options will be for couples who discover their future babies run a one-in-four chance of inheriting a serious or deadly genetic condition.

From a simple mouth swab or blood test 10,000 couples who are thinking about having a baby or in the early stages of pregnancy will be screened for roughly 500 severe or deadly recessive X-chromosome-linked gene mutations.

Rachael and Jonathan Casella did not know they were carriers of the SMA gene mutation.
Rachael and Jonathan Casella did not know they were carriers of the SMA gene mutation.  Photo: Supplied.

GPs, obstetricians, midwives, geneticists and genetic counsellors will begin recruiting couples towards the end of 2019 from specific sites across every state and territory. Couples can only be enrolled through health professionals involved in the study.

The project will be run by the national research network Australian Genomics Health Alliance in partnership with the University of NSW in Sydney, the Murdoch Children’s Research Institute in Melbourne and the University of Western Australia in Perth.

The Sydney sites involved in the trial include the Royal Hospital for Women, RPA, Nepean, Liverpool, Westmead and Blacktown Hospital.

 

Couples will be tested to see if they are carriers for Spinal Muscular Atrophy (SMA), cystic fibrosis and fragile X syndrome. The researchers were working on finalising the other "ultra rare" conditions that will be included from an original list of 3000 genes.

All couples will be offered information and support to help them decide whether or not to have the test, as well as the options available if they discover they are both carriers.

Advertisement

Couples who are found to have a high chance of having a child with one of the conditions will have free access to one cycle of implantation genetic diagnosis, in which they can choose to undergo IVF and have their embryos tested for the genetic conditions.

Pregnant women found to carry the same mutation can opt for further testing including amniocentesis and can consider termination.

Affected couples could choose to conceive without IVF and undergo prenatal testing or choose to test their child at birth. For some of these conditions, early diagnosis can lead to better treatments and quality of life.

Other couples might choose to use donor eggs, sperm or embryo. They might adopt or choose not to have children.

 

It is estimated that everyone carries three to five recessive genes for serious conditions. It is only when both parents carry the same mutation that their child has a one-in-four chance of developing the corresponding genetic condition, and a one in two chance their child will be a carrier.

Couples will only be told they have a genetic mutation if both individuals carry the same mutation for one of the conditions - roughly 1 per cent of all the couples tested, though some researchers suspect it could be as high as 3 per cent.

The trial will be led by by Professor Kirk at UNSW, Professor Nigel Liang at UWA and Professor Martin Delatycki at the Murdoch Children’s Research Institute and a steering committee of roughly 45 clinicians, scientists, genetic counsellors and pathologists across Australia.

Professor Kirk said the project would give couples the information and options, including better access to treatment and support, which would make a difference to the lives of thousands of future families.

"Part of my job is talking to couples whose children have these conditions. To do something really concrete towards a future where people like me don't have to breaking terrible news like that is a tremendous thing," Dr Kirk said.

The project was dubbed “Mackenzie’s Mission” by Health Minister Greg Hunt in honour of Rachael and Jonathan Casella’s baby girl Mackenzie who was diagnosed with SMA1 and died in October 2017 at seven months old.

“After Mackenzie’s diagnosis we knew we couldn’t change our family’s future but we could stop it from happening to other families,” Mrs Casella said.

“To have this carrier screening pilot project named after our daughter gives us such pride; to know she will live on through this legacy means everything to us,” she said.

The trial is designed to test the viability of a population-wide reproductive carrier screening program embedded within Australia’s healthcare system. The researchers will evaluate its cost-effectiveness, the psychological impact, ethics and potential barriers to screening.

Mackenzie’s Mission is part of the $500 million Australian Genomics Health Futures Mission - the largest investment by the federal government’s Medical Research Future Fund.

Mr Hunt has said he wants preconception carrier screening available free to all would-be parents who want it so that they can make informed reproductive choices.

Comments