A ground-breaking study into government-funded genetic carrier screening for Australian couples seeking to have children has published its main findings in the leading international journal, The New England Journal of Medicine.
The results of the Mackenzie’s Mission project demonstrate the feasibility of screening for the chance of having children with one or more of hundreds of genetic conditions at a national level and provide key information for the design of a potential public program in the future.
The study, administered by Australian Genomics, tested 9107 couples to see if they had an increased chance of having children with one or more of about 750 severe childhood-onset genetic conditions.
Of those couples tested, 1.9 per cent (175, or close to one in fifty couples) were found to be at “increased chance”.
Three quarters of them used that information to inform their decisions about having children, including using IVF and selecting embryos unaffected by the genetic condition.
It is the first time a genetic carrier screening project of this scale has been attempted in Australia and one of the first in the world. The three project leads were Professor Edwin Kirk (NSW Health Pathology, University of NSW), Professor Martin Delatycki (Victoria Clinical Genetic Services, Murdoch Children’s Research Institute) and Emeritus Professor Nigel Laing AO (Harry Perkins Institute of Medical Research, The University of Western Australia and PathWest Laboratory Medicine WA).
Until recently, people with an increased chance of having children with a severe genetic condition would most often only learn of their carrier status after the birth of an affected child. Reproductive genetic carrier screening (RGCS) gives couples the choice to have that information before or during early pregnancy.
The Mackenzie’s Mission project set out to find answers to many of the challenges involved in setting up a national program, including how to best offer it at population level, which genes to include, how laboratories report results, how couples respond once they discover they are at increased chance of having children affected by one of the conditions, and costs.
In November 2023 the Australian Government included reproductive carrier screening for three genetic conditions on the Medicare Benefits Schedule. This means screening is now free for spinal muscular atrophy, cystic fibrosis and fragile X syndrome, making Australia one of the few countries to fund RGCS.
But in the Mackenzie’s Mission study 80 per cent of the couples found to have an increased chance of bearing children with a severe genetic condition were carriers for conditions other than those three.
While RGCS is becoming more widely understood, it is still not routinely offered by all healthcare practitioners, and expanded carrier screening (covering hundreds of genes rather than just three) is only available on a fee-paying basis through a growing number of commercial providers. This means it is only available to those who can afford it.
The following quotes may be attributed to the respective research leads.
Professor Martin Delatycki (VIC)
“The Mackenzie’s Mission study had the largest number of genes tested for reproductive carrier screening of any study in the world.
“It has been a massive effort on the part of over 1000 healthcare professionals, researchers and diagnostic laboratory staff and others spread across all states and territories.
“Significantly, it showed that many couples embrace this type of screening, and most of those who find they have an increased chance of having children with a serious condition take steps to avoid this.”
Professor Edwin Kirk (NSW)
“We have come such a long way since the Mackenzie’s Mission project was first proposed. Our goal was to study how best to deliver reproductive genetic carrier screening for the Australian population, and the project taught us a great deal; as a result, we are well positioned to take the next step to a national program.
“The Federal Government’s decision last November to introduce free carrier screening for cystic fibrosis, fragile X syndrome and spinal muscular atrophy was a welcome step forward, and puts Australia in a leading position worldwide, as one of only a handful of countries offering government funded carrier screening.
“However, it is worth noting that 80 per cent of the couples identified in our study as having an increased chance for one of the screened conditions would not have been identified by the test now funded under Medicare. We look forward to continuing to work with the Government towards a fully funded screening program, so all Australians can have access to broad reproductive genetic carrier screening should they wish to.”
Emeritus Professor Nigel Laing AO (WA)
“One of the challenges of implementing a national screening program in Australia is delivering it across our diverse and geographically dispersed populations. The study demonstrated that this is possible by recruiting in all states and territories and in metropolitan, inner regional, remote and very remote locations, collaborating with a wide network of hospitals. In Western Australia this included working with the Royal Flying Doctor Service to take carrier screening to remote areas.
“Any new national program must include strategies to make carrier screening available to all regions of Australia, to all socioeconomic levels and to culturally, ethnically and linguistically diverse communities.”
Mackenzie Casella’s story
The Mackenzie’s Mission project was set up with the assistance of Rachael and Jonathan Casella. who learned their baby Mackenzie had spinal muscular atrophy (SMA) when she was 10 weeks old. SMA is a severe inherited neuromuscular condition without a cure.
Prior to her birth Rachael and Jonathan undertook all the recommended preparations and testing to have a healthy child. They have no family history of genetic conditions. They were not aware they are carriers of SMA. As carriers they do not have the condition themselves but have a one in four chance of having a child with SMA.
Mackenzie died in October 2017 when she was seven months old. Her journey was the catalyst for a campaign by Rachael and Jonathan to call for routine reproductive genetic carrier screening free for all prospective parents in Australia who wish to have this.
Rachael and Jonathan now have two healthy sons, Izaac and Joshua.
Image: (L-R) Martin Delatycki, Edwin Kirk, Rachel and Jonathan Casella, Nigel Laing.
