Alzheimer test could transform diagnosis

A Belfast doctor has received a US research award for his work on the development of a blood test for Alzheimer’s, something that could transform diagnosis of the disease by Marina Murphy STEPHEN TODD of the department of geriatric medicine at Queen’s University Belfast hopes to develop a blood test to diagnose Alzheimer’s disease. Currently, a definitive diagnosis of Alzheimer’s, the commonest cause of dementia (60 per cent of cases), is only possible at postmortem. “A blood test would be an exciting development, because it is easy to do and convenient for patients,” Todd says. Dementia currently affects more than 40,000 people in Ireland, according to the Alzheimer’s Society of Ireland. Demographic trends and increased life expectancy suggest that by 2026, 70,115 people will be affected, increasing to 104,000 by 2036. Todd was recently awarded the £228,000 (€283,000) Beeson Award, which is considered one of the most important prizes in geriatric medicine in the world. It is given by the American Foundation for Aging Research and Atlantic Philanthropies. Todd’s group has been studying the involvement of an enzyme called beta-secretase in the development of Alzheimer’s disease. An enzyme speeds up chemical reactions in the body. This particular enzyme is implicated in the formation of plagues and tangles of proteins in the brain. The presence of these plagues and tangles cause nerve cell death, eventually leading to the symptoms of dementia. In previous work, Todd’s group developed a method of measuring beta-secretase levels in platelets. Platelets are special types of cells in the blood that are normally involved in clotting. Using their new technique, the researchers found that beta-secretase levels in platelets were 17 per cent higher, on average, in patients with Alzheimer’s disease compared to controls. “Further work is needed on this test before it could be directly used in day-to-day clinical practice by doctors,” Todd says. “This is the basis of the work I will do with the Beeson scholarship.” Todd plans to contact the previous group of 200 patients and 200 healthy volunteers and ask their permission to do follow-up blood tests. The idea is to determine how beta-secretase levels might have changed in the five years since the previous study. It will also be possible to examine how drugs commonly used to treat Alzheimer’s disease affect platelet beta-secretase activity. This will be done simply by testing a group of patients before they start a drug regime and then testing again a few months later. “We might learn if we can better predict who will benefit from a particular drug and who won’t, Todd says. About 150 people will be recruited for this arm of the study. “Any test that makes it easier for doctors to correctly diagnose Alzheimer’s disease and predict how it will go or respond to treatment would be a big advance. We are far away from that goal at present and may not reach it with this particular test, but we have to try,” he says. Other groups have shown the beta-secretase levels are also increased in cerebrospinal fluid, the fluid that surrounds the brain and spinal cord inside the skull. But taking a sample of CSF would never be comfortable or convenient for patients. Research, such as this blood test, that might result in a reliable diagnostic process is to be welcomed, says Sarah O’Callaghan of the Alzheimer’s Society of Ireland. But, she says, it’s not clear how long it might be before an approved test might actually be available.