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Australians will soon have access to the first diagnostic blood test for Alzheimer’s disease that researchers say will transform early detection, treatment and potentially prevention.
The Therapeutic Goods Administration has approved a blood plasma test known as pTau217, paving the way for a blood test for Alzheimer’s disease to become part of routine GP health checks.
On Thursday, Health Minister Mark Butler will launch the new Asia-Pacific Centre of Excellence for Alzheimer’s Diagnosis in Sydney, capable of running the pTau217 test in 18 minutes, as well as processing a suite of other biomarkers linked to Alzheimer’s disease.
“I think it’s going to transform Alzheimer’s disease and eventually dementia,” said neurologist Dr Emma Devenney, who will oversee the new centre at Randwick – a collaboration between Neuroscience Research Australia (NeuRA) and Roche.
“It’s going to very quickly transform the field in terms of how we move towards prevention [and] move us much closer to early diagnosis, early treatments; and dementia and Alzheimer’s disease will become treatable.”
Dementia is the leading cause of death in Australia, and an estimated 446,500 Australians currently live with dementia. Alzheimer’s disease accounts for roughly two-thirds of cases, and there is no cure.
The current gold-standard diagnostic tools to confirm Alzheimer’s disease pathology are lumbar punctures to sample cerebrospinal fluid or specialised PET scans costing thousands of dollars.
Alzheimer’s disease is caused by the build-up of two proteins in the brain: amyloid-beta, which forms sticky plaques, and tau, which forms tangles inside neurons, disrupting cell-to-cell communication and causing neuronal death.
“We know that changes in amyloid and tau proteins happen 20 to 30 years before people develop symptoms, so that process has been going on for a long time [before people become symptomatic],” Devenny said.
The pTau217 test detects elevated levels of phosphorylated tau protein, a reliable biomarker for amyloid-beta plaques. Trials show the test has a diagnostic accuracy of about 90 per cent.
“Earlier diagnosis really gives people something incredibly valuable, which is time,” said Dr Anand Vairavan, Managing Director of Roche Diagnostics. “Time to understand what’s happening, time to plan for the future, and to access care and treatment sooner.”
Felicity Nicholson knows that an earlier diagnosis would not have solved everything for her husband, John Gethin-Jones.
“But it would have taken some of the heartache out of the long, painful process,” she said.
John was 60 when Nicholson noticed small signs. He could no longer write lovely messages in her birthday cards, held his knife and fork the wrong way up, and confused his right from his left. Now he cannot dress or feed himself.
It took two years to get John’s diagnosis after multiple assessments and scans.
“When we were finally told, he’s got Alzheimer’s, we still weren’t ready,” Nicholson said. “We just cried and cried and cried in the hospital foyer.
“If we had got an earlier diagnosis, he would have embraced life and used it differently. We would have had conversations about what John wanted, made better decisions … we didn’t even look at [care] homes. Whether it’s six months or a year, it’s a game-changer.”
In October, the TGA approved another blood test called pTau181, known as a “rule-out test” used as part of assessments for people with mild cognitive impairment to clear individuals without the Alzheimer’s pathology.
However, the pTau217 test is a “rule-out” and “rule-in” test that identifies people with Alzheimer’s pathology and those without it. A “grey zone” intermediate result suggests confirmatory tests are needed.
“It’s a better test,” said Professor Scott Ayton, director of the Centre of Research Excellence in Enhanced Dementia Diagnosis at the Florey Institute.
The pTau217 test has typically been useful to confirm a diagnosis of Alzheimer’s in people with symptoms.
“In the future, it might be used for screening for the early stages of Alzheimer’s disease even before they present with symptoms,” said Ayton, who leads a study that makes the test available to clinicians working up patients who may have Alzheimer’s disease.
The TGA approval means, for the first time, the test can be used clinically.
“As a researcher I’m really excited by this, but I’m also cautious about everyone in the community knocking on their doctor’s door to say, ‘I want this blood test’,” Ayton said. “There is still a developmental training phase to be rolled out over several years.”
NeuRA is leading the development of national guidelines that will set the parameters for the blood test’s use, including who to test and when.
The centre will process blood tests and cerebrospinal fluid samples for clinical trials. Clinicians are expected to be able to refer patients in six to nine months.
NeuRA CEO Professor Matthew Kiernan said the centre would create clinical pathways to receive blood samples from doctors across Australia and the Asia-Pacific.
The centre would produce the reference information for pTau217 necessary to apply for a Pharmaceutical Benefits Scheme listing.
“Then any doctor in Australia can order it,” Kiernan said.
“For a long time, there was this feeling that there wasn’t much that we could do, but that has changed so much,” Kiernan said. “An earlier diagnosis means people can access the right supports earlier … we have disease-modifying therapies, and we know the sooner we start those, the better the outcome will be.”
Studies of recently approved amyloid-targeting therapies lecanemab and donanemab have shown a modest effect at slowing down cognitive impairment.
Ayton said: “The hope of the field is that if we intervene even earlier, then we might be able to stop the development of Alzheimer’s disease.”
Devenney is also leading an investigation aimed at detecting Alzheimer’s pathology in people with early-onset genetic dementia, and treating them with amyloid-targeting drugs before they develop symptoms.
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