Scientists believe one of the reasons drug trials for Alzheimer's disease yield poor results is because drugs are given too late in the development of the disease, which is notoriously difficult to diagnose early. Now a new study (led by King's College London in the UK and the British company Proteome Sciences) suggests this might be about to change - the researchers identified a group of 10 proteins in the blood that they believe can predict the onset of Alzheimer's disease.
The study is the largest of its kind so far and involved over 1,000 participants. The idea is to use the blood test to identify patients to join clinical trials testing drugs that halt progression of Alzheimer's.
The news follows recent reports from others who are taking steps to improve the diagnosis of Alzheimer's disease.
In March 2014, researchers in the US said they were getting closer to a new blood test for Alzheimer's when they reported in Nature Medicine how they identified and validated 10 biomarkers that can predict with 90% accuracy whether a healthy person will develop Alzheimer's or cognitive decline within 3 years.
Meanwhile, in a position paper published recently in The Lancet Neurology, an international team of experts reveals its proposals for a simpler, more reliable approach to diagnosing Alzheimer's disease that promises to reduce the current 33% misdiagnosis rate.
Currently no simple, reliable way to predict whether MCI will develop into dementia
Alzheimer's disease is the most common form of dementia - a syndrome that affects thinking, memory, behavior and autonomy. Global estimates suggest by 2050, there will be 135 million people with dementia, and in 2010 the total annual global cost of dementia was thought to be about $604 billion.
Mild cognitive impairment (MCI) - which includes problems with day-to-day memory, attention and language - can be an early sign of dementia, but it can also be a symptom of stress or anxiety.
About 10% of people with MCI go on to develop dementia within a year. However, apart from regular memory tests, there is currently no reliable way to predict who will and will not be among them.
For this latest study, the team analyzed blood sample results from three international studies covering a total of 1,148 individuals: 476 with Alzheimer's disease, 220 with MCI, and 452 elderly people without dementia who acted as controls. Also, 476 individuals across the three groups had also undergone MRI brain scans.
The team analyzed 26 proteins in the blood samples and found that 16 linked strongly to brain shrinkage in the MCI and Alzheimer's groups.
Progression of MCI to Alzheimer's within a year predicted with 87% accuracy
In a second analysis, they discovered a combination of 10 proteins could predict whether individuals would progress from MCI to Alzheimer's disease within a year with an accuracy of 87%.
Lead author Dr. Abdul Hye, of King's Institute of Psychiatry, says the study marks the end of many years' work to find which of the thousands of proteins in the blood were clinically relevant, and adds:
"We now have a set of 10 proteins that can predict whether someone with early symptoms of memory loss, or mild cognitive impairment, will develop Alzheimer's disease within a year, with a high level of accuracy."
Senior author Simon Lovestone, a professor at the University of Oxford, led the study while at King's. He explains that Alzheimer's starts to affect the brain years before patients can expect to receive a diagnosis, and:
"Many of our drug trials fail because by the time patients are given the drugs, the brain has already been too severely affected. A simple blood test could help us identify patients at a much earlier stage to take part in new trials and hopefully develop treatments which could prevent the progression of the disease."
Initial value of test will be for clinical trial selection
The team now plans to validate the findings in further sample sets and improve the accuracy and reduce the risk of misdiagnosis. The final aim is to develop a simple, reliable test that doctors can use.
But Dr. Eric Karran, director of research at Alzheimer's Research UK says "we're not currently in a position to use such a test to screen the general population," and sees initially, the value of the test will be to "improve clinical trials for new treatments and help those already concerned about their memory."
Research suggests PET brain scans and tests on plasma in lumbar fluid can also predict the onset of dementia from MCI, but PET imaging is highly expensive and lumbar punctures are invasive.
Co-author Dr. Ian Pike, of Proteome Sciences, says "a blood test will be considerably easier and less expensive than using brain imaging or cerebrospinal spinal fluid."
He says they are currently selecting commercial partners to work with on a blood test for the global market.
Written by Catharine Paddock PhD