Blood test for Alzheimer's disease 'highly accurate'

Researchers say a new blood test for Alzheimer's disease has been shown to be highly accurate in detecting people with early symptoms.

Scientists looked for two proteins - amyloid beta 42/40 and p-tau217 - and found the test was 95% accurate in identifying patients with existing cognitive impairment linked to the condition. The US study involved 509 patients in an outpatient memory clinic in Florida and was published in the medical journal Alzheimer's and Dementia.

The test, which has already been approved by the US regulator, was also 82% accurate for specificity, which means it could rule out people without dementia. Dr Gregg Day, who led the study, said the test was as good as existing, but more invasive, tests.

He said the next step was to extend the test to a wider range of patients, including those with early Alzheimer's who do not have any cognitive symptoms. Scientists say the two proteins, which they have identified in blood plasma, are associated with the buildup of amyloid plaques.

Amyloid protein can be found in our brains, but in Alzheimer's disease, amyloid sticks together and forms abnormal deposits, which are thought to be toxic to brain cells. Dr Richard Oakley, associate director for research and innovation at the Alzheimer's Society in the UK, said the results "suggest this test is very accurate".

"Blood tests will be critical to accelerate diagnosis and give more people access to the care, support and treatments they desperately need faster than ever before," he added. Read more:Dementia risk link to sleep problemsBrain injury costs for ex-footballersFormer player shares dementia fears In the UK, the Blood Biomarker Challenge is a multi-million-pound research programme supported by the Alzheimer's Society, Alzheimer's Research UK and the National Institute for Health and Care Research.

Its goal is to bring blood tests for dementia diagnosis to the NHS by 2029. Dr Julia Dudley, head of research at Alzheimer's Research UK, said: "We urgently need to improve how we diagnose dementia and it's great to see international research working towards this goal." She said the studies like the Blood Biomarker Challenge are a "crucial part of making diagnosis easier and faster, which will bring us closer to a cure".

"The study is testing blood tests, including p-tau217, in thousands of people from sites across the UK," she added..