Blood test can detect onset of Alzheimer’s

A simple blood test that can detect the onset of Alzheimer’s has been developed by scientists in a breakthrough for combating the disease.

The test could speed up diagnosis in GP surgeries and boost the development of drugs to tackle the condition. At present there is no effective treatment.

Researchers showed that the test had more than 90 per cent accuracy in spotting toxic proteins in the brain that can be an early indication of the disease. This could enable doctors to identify the illness before memory loss or mental decline.

Randall Bateman, from Washington University School of Medicine and one of the scientists behind the test, said that the procedure could be in use in little more than a year as a means of recruiting people en masse for clinical trials.

Alzheimer’s spreads in the brain for years and even decades before symptoms appear. Billions of pounds have been invested in drugs to tackle beta amyloid, the protein believed to be its primary cause, but all trials have failed. Many researchers think this is because the drugs were used too late and that interventions will work only if the disease is caught before it has caused extensive brain damage.

By spotting the beta amyloid years earlier, scientists hope that the test will allow them to measure these interventions in cognitively normal people.

Although brain scans known as Pet scans can also be used to identify the build-up of these proteins in the brain, they are too costly and time consuming to be used at scale. This has made the search for a quick early diagnostic tool one of the key goals of Alzheimer’s research, with backing from all the big dementia charities as well as the Bill and Melinda Gates Foundation.

Bateman said that his blood test, details of which were published in the journal was sufficiently advanced that it might be the answer.

‘‘The big benefit with this test is that you can run trials much faster, recruit and identify people much more quickly,’’ he said.

‘‘If we are running 50 per cent more trials we will get to effective therapies much faster. To me that translates into helping millions of people.’’

The study involved 158 older people, who had both Pet scans and blood tests. Most appeared cognitively normal at the start of the study, but the Pet scan showed some had the protein build-up that is characteristic of the very early stages of Alzheimer’s. He and his colleagues found that the verdict of the blood test corresponded with that of the Pet scan, considered the gold standard, 90 per cent of the time.

There was also evidence that when it did not give the same answer it was because the Pet scan was wrong, rather than the blood test.

‘‘What we found was that if a blood test was abnormal and the Pet said normal, more than half the time the blood was correct.’’

Later, people’s Pet scans became abnormal.