Caroline Zielinski
Australian doctors will follow their US counterparts and hope to soon be able to test for Alzheimer’s using a simple blood test, perhaps by the end of the year.
The test, like so much medicine, is extremely expensive, and probably wont be made available for people in less developed countries, where more than half the cases are.
The test will identify a blood protein called phosphorylated tau, or p-tau, which increases at the same time as other damaging proteins — beta amyloid and tau — build up in the brains of people with Alzheimer’s.
Dementia Australia says Alzheimer’s disease is the most common form of dementia and is a physical brain condition resulting in impaired memory, thinking and behaviour.
An estimated 6.7 million Americans age 65 and older are living with Alzheimer’s dementia which was officially listed as the sixth-leading cause of death in the United States.
The WHO says there are more than 55 million people with dementia worldwide, over 60% of whom live in low-and middle-income countries. Every year, there are nearly 10 million new cases.
Dementia is currently the seventh leading cause of death and one of the major causes of disability and dependency among older people globally.
In 2019, dementia cost economies globally 1.3 trillion US dollars, approximately 50% of these costs are attributable to care provided by informal carers (e.g. family members and close friends), who provide on average 5 hours of care and supervision per day.
WHO
Colin Masters, Professor of dementia research at The Florey brain research institute in Melbourne and a consultant at the Royal Melbourne Hospital, says he expects blood tests to largely replace the current gold standards of PET imaging and cerebrospinal fluid (CSF) tests from lumbar puncture.
“A blood sample is cheaper, and you can do the same sort of analysis and have the same turnout time as a CSF test,” he tells Cosmos.
While an Alzheimer’s blood test has already been made available in the US direct to consumers through a company called AD-Detect.
A study by researchers at the University of Gothenburg in Sweden, published in late January in JAMA Neurology, was the first to compare it to the PET scan and the CSF test.
Working together with ALZPath, a company that developed a blood-based Alzheimer’s test used in research studies, the researchers analysed scans or CSF and blood samples from nearly 800 people from American, Canada and Spain.
They found the blood test performed just as well when it came to diagnosing Alzheimer’s disease.
A test for Alzheimer’s
Study co-author Nicholas Ashton, an Associate Professor of Neurochemistry at the University Gothenburg, says the blood test will arm doctors with more information when it comes to diagnosing and treating symptoms of Alzheimer’s.
“In an ideal scenario, most people would receive a PET scan or CSF … in reality, less than 5% of those suspected to have Alzheimer’s are tested,” he tells Cosmos.
While both tests are good at picking up whether someone has Alzheimer’s (in conjunction with cognitive function assessments and a thorough medical history investigation) they are expensive and invasive.
Health and lifestyle factors that may contribute to the development of Alzheimer’s disease include:
Health and lifestyle factors that may contribute to the development of Alzheimer’s disease include:
- physical inactivity
- lack of mental exercise
- smoking
- obesity
- diabetes
- high cholesterol
- high blood pressure.
Positron Emission Tomography (PET) scans are used to measure the concentration of the build-up of abnormal amyloid protein in the brain, They are complex and costly to execute, requiring injections and an MRI.
Masters says that in Australia, PET scan costs in excess of $4,000 per person, while Ashton pegs the price point closer to $7,700 per patient in Europe.
The second test – CSF – is an invasive procedure called a lumbar puncture, or spinal tap, where a person’s spinal fluid is taken out and analysed for the presence of tau and beta-amyloid, two markers that form abnormal brain deposits strongly linked to Alzheimer’s.
While it is not as expensive as a PET scan, not many people want to receive a spinal tap.
“The blood test assesses the combination of amyloid and p-tau, and the technology to do it is becoming more accurate with less variability,” Masters says. “We are doing the research on this test right now in Australia, and we expect to be running clinical blood tests in Australia before the end of year.”
An easily accessible blood test is the first step to figuring out whether people should be prescribed lecanemab, an Alzheimer’s drug that works by removing amyloid protein from the brain, before the onset of symptoms.
While the drug is not yet available to the general public in Australia (only through clinical trials, of which there are currently four) it was approved by the American Food and Drug Administration (FDA) in January 2023 after data showed it can slow Azheimer’s-associated cognitive decline by 27% in the early stages of the disease.
At the moment, lecanemab is only prescribed to people in the US with very mild symptoms of memory and cognitive problems who have been tested by a PET scan, and shown to have amyloid build-up in the brain.
And while there are clinical trials currently looking at the preventive measures of using lecanemab in people with amyloid build-up and increased risk of Alzheimer’s disease but no symptoms (research suggests that the formation of amyloid plaques or tau tangles start a decade or more before symptoms) debate continues around whether it is ethical or medically meaningful to use the drug before symptoms begin.
“We know that amyloid plaque build-up drives the process and that the second protein, tau, comes in when symptoms start,” says Ashton.
“All of our research shows that amyloid build-up is not good for us, so why shouldn’t we use lecanemab to clear some of it? If you have high blood pressure mid-life, you treat the blood pressure because you know it’s not good for you. I see it the same way with lecanemab.
“It doesn’t have to be a lifetime treatment; you can just go on and off it when you need to.”
Masters adds that the drug not only slows progression of Alzheimer’s if taken early in the course of the disease, but that in some cases, researchers are seeing “actual reversal of cognitive change”.
But because we don’t yet have results showing that lecanemab is clinically useful in people who have yet to suffer symptoms, he says it remains unclear how the drug would work long term.
“At the moment, if you have mild Alzheimer’s in the US, you have an injection roughly once a month. We don’t know how long this will go on, whether it’s for the rest of your life or whether you’d go on and off as you drive the amyloid down to normal levels,” Masters says.
While he’s confident the drug will be available in Australia by the end of the year, how much it will cost, who will be able to get it and which tests are needed to enable access will be determined by Australia’s drug regulator, the Therapeutic Goods Administration (TGA).
“In America, the drug’s starting price is $US26,000 for a single series of doses for one year, even though the health insurance pays for it. When it gets registered in Australia, the cost will depend on whether it’s covered by the Pharmaceutical Benefits Scheme”, Masters adds.
“Really, we are just beginning to find all this out.”
