ALZHEIMER’S DISEASE

A SIMPLE blood test can detect Alzheimer’s disease up to 15 years before symptoms begin, a major trial has found. It paves the way for a national screening programme.

The trial found that the test was as accurate as the current gold standard for diagnosing the condition.

For the first time, doctors were able to say if a person had a high, medium, or low chance, of having the disease – ruling out further invasive procedures.

Experts have said it would “revolutionise” diagnosis, making Alzheimer’s as easy to test and detect as for other routine health conditions such as high cholesterol.

Patients could expect results within days of visiting their GP, rather than the years it currently takes to get a diagnosis. This could have huge implications for future treatments, removing the barriers for a diagnosis – such as long waits for spinal taps or brain scans – and speeding up trials.

It could also pave the way for screening over-50s once more effective treatments become available.

Made by diagnostics company ALZpath, it was found to be 97 per cent accurate at detecting traces of the “tau” protein, which was linked to developing Alzheimer’s disease during the eight-year trials. These proteins start to build up on the brain 10 to 15 years before symptoms start showing.

Researchers in Sweden found high levels of the “tau” protein in the blood test corresponded to high levels of Alzheimer markers seen in expensive diagnostic brain scans and painful lumbar punctures.

The more of this leaked “tau” brain protein in the blood, the more likely or advanced the Alzheimer’s disease was in the tests involving 786 people. Growing evidence suggests biomarker changes like these can be detected in the blood years before other signs of the disease appear in the brain.

It means if scientists can find a way to stop these protein levels from rising, they could effectively halt Alzheimer’s in its tracks.

With breakthrough treatments such as donanemab and lecanemab on the horizon, experts say it is vital to have quick and reliable diagnoses. Professor David Curtis of University College London Genetics Institute said this was “one half of the solution”, while we await effective treatments.

He added: “This potentially could have huge implications. Everybody over 50 could be routinely screened every few years, in much the same way as they are now screened for high cholesterol.”

Around 900,000 people in the UK live with dementia – with Alzheimer’s the most common form. The growing ageing population means numbers are expected to rise to 1.6million by 2040, making a cheap screening tool vital to get to grips with the challenge.

Alzheimer’s Research UK analysis found 74,261 people died from dementia in 2022 compared with 69,178 a year earlier, making it the country’s biggest killer. While previous blood tests have shown promise, these findings have caused particular excitement given the high accuracy levels, large study size, and because the test already exists commercially.

It is also the first time a blood test has been found to be at least as good as a painful lumbar puncture or spinal tap for detecting elevated levels of the tau protein, according to the research team at the University of Gothenburg, Sweden.

Lumbar punctures involve taking fluid from the patient’s spinal cord. The inexpensive tests – priced at around £150 – could also be used to monitor a patient’s condition, allowing more tailored trials or treatment in future.

Dr Richard Oakley, of the Alzheimer’s Society, urged that more research would be needed, but said: “This study is a huge welcome step in the right direction as it shows that blood tests can be just as accurate as more invasive and expensive tests.

“It suggests results from these tests could be clear enough to not require follow-up investigations for some people living with Alzheimer’s disease, which could speed up diagnosis.”

The tests would need regulatory approval before widespread use. But they could form part of NHS trials starting imminently and looking to roll out blood tests for Alzheimer’s within the next five years.

The scientists’ findings were first published in JAMA Neurology.