Research just published in the leading international journal “Alzheimer’s Research and Therapy” outlines research on the effectiveness of a blood test in identifying the presence of Alzheimer’s disease. The research carried out in the Institute of Memory and Cognition at Tallaght University Hospital looked at the performance of a new blood test (plasma p-tau217) to detect the amyloid plaques that build up in the brain in people with Alzheimer's disease. As things currently stand, amyloid plaques can only be detected by lumbar puncture (spinal tap) to get a sample of cerebrospinal fluid - which are invasive - and through scans that are very limited in their availability.

The use of blood tests has clear advantages over both of these methods – they are less invasive and more straightforward for patients, easier to scale up and are less costly. The study, led by Dr Adam Dyer, Geriatric Medicine Trainee (Specialist Registrar/SpR), Tallaght University Hospital and Medical Gerontology, Trinity College Dublin, examined the performance of this new blood test (plasma p-tau217) by using samples from the biobank which has been established at the TUH Institute of Memory and Cognition. As part of this biobank, patients who have symptoms and are undergoing a diagnostic lumbar puncture for the detection of Alzheimer’s disease opt to donate cerebrospinal fluid and blood samples for future research. This is crucial in examining the performance of these new blood tests in real-world clinical cohorts.

The research examined how well the new blood test (plasma p-tau217), performed in detecting the same proteins - in particular the amyloid protein which is the main constituent of plaques in Alzheimer’s disease. These are looked for in cerebrospinal fluid (using a lumbar puncture) in samples from the existing biobank. Overall, the blood test (plasma p-tau217) was over 90% as accurate as performing the lumbar punctures in detecting the amyloid protein.

Different blood test cut-off values were then examined and it was found that if - theoretically - the blood test was used in the future, over half of lumbar punctures could be avoided. This has significant implications in terms of invasiveness, length of time to a diagnosis and also may reduce cost. Lumbar punctures are safe and well-tolerated as diagnostic procedures, however a small number of individuals may experience side-effects such as post lumbar-puncture headache.

Commenting on the research Dr Dyer said that the study found that “blood tests such as plasma p-tau217 demonstrate excellent performance to detect the changes that are characteristic of Alzheimer’s disease. In the future, clinical use of these blood tests may enable us to avoid invasive tests such as lumbar punctures in over half of individuals who currently have these procedures performed”.

First Irish study

This research is one of a handful in the world to assess this in real-world clinical cohorts and the first Irish study to examine the performance of these blood tests. The next steps for this research is to examine if the performance of these blood tests can be matched in diagnostic laboratories, meaning that patients referred can hopefully have a blood test in the first instance.

This would mean that those who clearly have a negative or positive result could avoiding the need for diagnostic lumbar puncture.  Commenting on the research, Professor Seán Kennelly, Consultant Physician in Geriatric Medicine and Director of the Institute of Memory and Cognition noted that “a timely and accurate diagnosis of Alzheimer’s disease is of paramount importance to living well with this condition, and our ability to support diagnosis using a simple blood test like this has the potential to revolutionise this area for affected people. We are so grateful to the people attending our clinical services, as none of this research would be possible without their generosity in agreeing to participate, which is such an important role of a teaching hospital”.

Dr Adam Dyer is a Geriatric Medicine Trainee (Specialist Registrar/SpR) and PhD student under the supervision of Prof Seán Kennelly in the Institute of Memory and Cognition at TUH and Trinity College Dublin. The new blood test (plasma p-tau217) was measured in Professor Nollaig Bourke’s laboratory in Trinity College Dublin (TCD).