An international trial is examining whether a finger-prick blood test could be used to help diagnose Alzheimer's disease.

The study, involving 1,000 volunteers aged over 60 in the UK, US and Canada, will aim to detect biomarkers associated with the condition.

Dr Michael Sandberg, a London GP, was encouraged to take part in the study after witnessing his mother's slow decline from Alzheimer's disease. He had a negative result from the tests and said it was "a huge relief".

The Bio-Hermes-002 study is led by the medical research charity LifeArc and the Global Alzheimer's Platform Foundation, with support from the UK Dementia Research Institute.

Dr Giovanna Lalli, director of strategy and operations at LifeArc, said: "We are looking at the presence of three proteins that have been linked to Alzheimer's disease, so-called blood-based biomarkers.

"By analysing the concentration and the levels of these proteins it may tell us whether a person is at risk of developing Alzheimer's disease."

Studies have shown that rogue proteins called amyloid and tau can accumulate in the brains of individuals over 15 years before they start to display symptoms of Alzheimer's, the most common form of dementia.

All the volunteers will have the current gold-standard tests for Alzheimer's which involve a specialised brain PET scan using a radioactive tracer, or a lumbar puncture to remove a sample of cerebrospinal fluid.

Such tests are expensive, time-consuming and invasive and only two in 100 Alzheimer's patients are offered them, so the hope is that the finger-prick test could help revolutionise how the disease is identified.

Prof Fiona Carragher, chief policy and research officer at the Alzheimer's Society, said, with tests not currently widely available across the UK, "getting an accurate diagnosis takes far too long".

She added: "With new treatments on the horizon, early and accurate diagnosis must be a priority for the NHS. That's why we're funding work to bring blood tests for dementia to the NHS, so everyone who would benefit from a diagnosis can get one quickly and accurately."

Trial participant Sandberg told the BBC: "My mother did very well on a trial and that encouraged me to take part.

"I believe knowledge is power and am really excited that you may be able to screen people at risk of dementia without expensive scans or needles."

When Sandberg was given his results, both the brain scan and the finger-prick test were negative. He said: "It's a huge relief, knowing what my mother went through".

This is - of course - just one set of results. Scientists will need to analyse the findings from all 1,000 volunteers on the trial before they know how useful the finger-prick blood test is at spotting the risk of Alzheimer's.

Dr Emer MacSweeney, a neuro-radiologist at ReCognition Health, is recruiting some of the UK volunteers.

She said: "If this is successful, it provides a ubiquitous, accurate test which can detect the presence of abnormal amyloid protein in the brain without complicated, expensive investigations."

Using biomarkers in the blood to identify Alzheimer's risk is a rapidly developing field of research.

Last year US regulators approved a blood test for diagnosing Alzheimer's disease. That involves a traditional blood draw using a needle and syringe.

Another study is under way in the UK looking at whether using blood tests improves both the diagnosis and treatment in real-world settings.

A key advantage of the finger-prick test would be that it could be carried out by individuals at home, and the sample be posted to a lab for analysis, as it does not require refrigeration.

There are hopes that blood tests could eventually be used as a screening tool for dementia for older adults.

To date, the study has enrolled 883 of the 1,000 participants with more than 360 completing all the tests.

This includes a mix of cognitively normal and mildly impaired people and some with early-stage Alzheimer's.

At least 25% of volunteers will be from under-represented groups. The trial is expected to complete in 2028.