Dementia breakthrough: Alzheimer’s blood test ‘94% accurate in early diagnosis’

Alzheimer’s disease is the most common form of dementia and while damaging clumps of protein that lead to the development of the disease are known to build up in the brain up to 20 years before people experience symptoms such as memory loss and confusion, researchers have developed a new blood test that can detect early brain changes associated with the cognitive condition.

The blood test is 94 per cent accurate and is one step closer to clinical use after researchers from Washington University School of Medicine found a way to measure levels of the Alzheimer’s protein amyloid beta in the blood – and whether or not the protein has accumulated in the brain.

The new findings, published in the Neurology Journal, reveal the blood test could be available within a few years and offer another way of detecting the beginnings of amyloid deposition in the brain – which is currently detected through a PET brain scan. While there’s currently no cure for Alzheimer’s, it could allow those showing early signs of the disease to participate in clinical trials or start other treatments that can lessen symptoms.

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“Right now we screen people for clinical trials with brain scans, which is time-consuming and expensive, and enrolling participants takes years,” senior author Randall J. Bateman said in a statement. “But with a blood test, we could potentially screen thousands of people a month. That means we can more efficiently enrol participants in clinical trials, which will help us find treatments faster, and could have an enormous impact on the cost of the disease as well as the human suffering that goes with it.”

The new blood test uses a technique called mass spectrometry to measure the levels of two forms of amyloid beta in the blood. The ratio of the two forms goes down as the amount of amyloid beta deposits in the brain increase. The current study analysed 158 over-50s who each underwent a PET brain scan and provided at least one blood sample so researchers could classify each blood sample and scan as either amyloid positive or negative.

While 88 per cent of the blood tests matched with the pet scan, researchers also incorporated major risk factors for Alzheimer’s including age, genetics and gender and found that when people were over 65 or had a genetic variant called APOE4, the accuracy of the blood test increased to 94 per cent.

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“Sex did affect the amyloid beta ratio, but not enough to change whether people were classified as amyloid positive or amyloid negative, so including it didn’t improve the accuracy of the analysis,” first author Suzanne Schindler explained.

And, while the results of some blood tests were initially considered false positives because they didn’t match results from the brain scan, researchers said these people ended up testing positive for amyloid better when their brain scans were taken four years later, suggesting that the initial blood tests could have flagged early signs of Alzheimer’s that the PET scan didn’t detect.

There have long been calls for Alzheimer’s treatments to begin as early as possible because when people begin showing symptoms such as forgetfulness, their brains are already so severely damaged that therapy is unlikely to have significant impacts. Experts believe this could also save money.

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“Reducing the number of PET scans could enable us to conduct twice as many clinical trials for the same amount of time and money. It’s not the US$4,000 (AU$5,878) per PET scan that we’re worried about,” Bateman said. “It’s the millions of patients that are suffering while we don’t have a treatment. If we can run these trials faster, that will get us closer to ending this disease.”

Do you know someone who is impacted by dementia? How were they diagnosed?