As the number of genetic abnormalities that can be identified in pre and post pregnancy tests reaches the thousands, a national project has been launched to assist doctors as they navigate the complex world of genetic testing and disease diagnosis.
Couples planning a baby or in the early stages of pregnancy can be screened for an increasingly large number of genetic abnormalities that could affect their baby, but which tests are best for each couple?
Gone are the days when the routine scan for Down Syndrome, offered to couples in Australia for over 50 years, was the only standard genetic screening test in early pregnancy. Now saliva or blood tests for genetic conditions caused by more than 1200 genes can be offered by doctors.
Since November 2023 a Medicare rebate is available for the three-disease carrier screen looking specifically at the genes for Cystic Fibrosis, Fragile X and Spinal Muscular Atrophy, considered the most common recessive diseases.
Perth GP and UWA Clinical Senior Lecturer of General Practice, Associate Professor Lucy Gilkes says the challenge for GP’s and obstetricians is there are so many genetic variants that can be screened for but little information is provided to guide doctors on what to offer.
“Some conditions are more prevalent in some racial ethnicities. Some pathology laboratories test a certain selection of DNA mutations while another lab may offer a different selection.
“One doctor may only offer the non-invasive prenatal testing (NIPT), a blood test primarily used for Down Syndrome, whereas another doctor may offer NIPT as well as screening for a wider range of genetic disorders.
“Currently there are no set guidelines in Australia, no national centralised source of material for doctors to support them in advising and counselling couples”, she said.
Internationally regarded geneticist Emeritus Professor Nigel Laing AO at the Harry Perkins Institute of Medical Research ran one of Australia’s earliest pre-pregnancy genetic carrier screening pilot studies which was offered in the Busselton region in 2018.
“Our pilot study found that pre-pregnancy carrier screening can be implemented through general practices, when there is the right level of support.”
“However, without support, it can be challenging for doctors.
“For example, after our Busselton study we were involved in the national Mackenzie’s Mission screening program from 2020 to 2022 which was a study to investigate the best way to deliver reproductive genetic carrier screening for almost 1300 genes responsible for around 750 genetic conditions including Cystic Fibrosis, Fragile X and Spinal Muscular Atrophy.
“We heard from couples that they’d been told by their doctor that they didn’t need the test for Down Syndrome because they’d had the Mackenzie’s Mission test, even though that genetic carrier screening test did not screen for Down Syndrome.
“This level of confusion and misinformation puts couples at risk”, he said.
“Genetic screening is not a simple tick the box exercise for a GP. Cystic Fibrosis for example has a Medicare rebate where maybe 50 genetic abnormalities are screened for, but there are hundreds more genetic variants that can be analysed. How is a doctor meant to know the extent of screening undertaken by each pathology laboratory? How is a couple to know if they’ve had the most comprehensive or appropriate screening or not?” he said.
Professor Laing, Dr Gilkes and genetic counsellor Samantha Edwards at the Harry Perkins Institute are contributing to the national project to develop best practice implementation of genomic tests in Australia.
“From our experience in running both the Busselton pilot study and Mackenzie’s Mission in WA we will be recommending ways to support doctors such as providing them access to WA based genetic counsellors through a national hotline, having a national central source of information and rolling out education programs about the best tests to order for couples with, say, a particular family history or who are from a particular ethnic background,” he said.
The national project is expected to take three years.
