Scientists have identified a set of 10 proteins in the blood which can predict the onset of Alzheimer's, marking a significant step towards developing a blood test for the disease.
There are currently no effective long-lasting drug treatments for Alzheimer's, and it is believed that many new clinical trials fail because drugs are given too late in the disease process. A blood test could be used to identify patients in the early stages of memory loss for clinical trials to find drugs to halt the progression of the disease.
“Alzheimer's begins to affect the brain many years before patients are diagnosed with the disease,” said Professor Simon Lovestone of the University of Oxford, who led the work while at King's College London. “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. The next step will be to validate our findings in further sample sets, to see if we can improve accuracy and reduce the risk of misdiagnosis, and to develop a reliable test suitable to be used by doctors.”
The study, led by King's College London and UK proteomics company, Proteome Sciences plc, analyzed over 1,000 individuals and is the largest of its kind to date.
The researchers used data from three international studies. Blood samples from a total of 1,148 individuals (476 with Alzheimer’s disease, 220 with “mild cognitive impairment,” and 452 elderly controls without dementia) were analyzed for 26 proteins previously shown to be associated with Alzheimer's disease. A sub-group of 476 individuals across all three groups also had an MRI brain scan.
Researchers identified 16 of these 26 proteins to be strongly associated with brain shrinkage in either mild cognitive impairment or Alzheimer's.
They then ran a second series of tests to establish which of these proteins could predict the progression from mild cognitive impairment to Alzheimer's. They identified a combination of 10 proteins capable of predicting whether individuals with mild cognitive impairment would develop Alzheimer's disease within a year, with an accuracy of 87%.
Dr. Abdul Hye, lead author of the study from the Institute of Psychiatry at King's College London, said, “Memory problems are very common, but the challenge is identifying who is likely to develop dementia. There are thousands of proteins in the blood, and this study is the culmination of many years' work identifying which ones are clinically relevant. 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.”
Dr. Ian Pike from Proteome Sciences said, “We are in the process of selecting commercial partners to combine the protein biomarkers in a blood test for the global market, a key step forward to deliver effective and early treatment for this crippling disease.”
Alzheimer's disease is the most common form of dementia. Globally, it is estimated that 135 million people will have dementia by 2050. In 2010, the annual global cost of dementia was estimated at $604 billion.
Mild cognitive impairment includes problems with day-to-day memory, language and attention, and can be an early sign of dementia, or a symptom of stress or anxiety. Approximately 10% of people diagnosed with mild cognitive impairment develop dementia within a year. But apart from regular assessments to measure memory decline, there is currently no accurate way of predicting who will, or won't, develop dementia.
Director of Research at Alzheimer's Research UK, Dr. Eric Karran, said, “As the onset of Alzheimer's is often slow and subtle, a blood test to identify those at high risk of the disease at an early stage would be of real value. Detecting the first signs of Alzheimer's could improve clinical trials for new treatments and help those already concerned about their memory, but we’re not currently in a position to use such a test to screen the general population.”
The findings are published in the journal Alzheimer's & Dementia, and the study was funded by Alzheimer's Research UK, the UK Medical Research Council, the National Institute for Health Research (NIHR) Maudsley Biomedical Research Centre and Proteome Sciences.