Diagnosing the silent killer Alzheimer’s

Diagnosing the silent killer Alzheimer’s

La Trobe University’s Professor Andrew Hill and Dr Lesley Cheng are conducting vital research into developing a blood test to diagnose the neurodegenerative disease, Alzheimer’s.

Alzheimer’s and dementia are the second leading cause of death among Australians. Alzheimer’s affects about one in ten people around the age of 65 and rises dramatically to one in three for those in their 80s, says Dr Cheng.

With Australia’s aging population on the increase, it’s estimated to affect half a million by 2050. It’s essential we find effective ways to diagnose, treat and prevent this silent killer.

Hi, Dr Cheng. What are the limitations or challenges with the current method of diagnosing Alzheimer’s?

When a patient experiences symptoms such as consistent memory loss, a physician or specialist may perform a neuropsychological test, which is essentially a memory test to assess cognitive function.

It assesses how well you can recall things, word-image association, problem-solving skills and simple maths – things like that. You could imagine that even young people could get that wrong. There’s some flaws to that method and it can be quite subjective.

The other confirmed way is only after death through an autopsy, where the pathologist looks for the toxic protein that is involved with Alzheimer’s disease, amyloid beta. It’s only through the autopsy that they can confirm someone has died from or had Alzheimer’s disease.

So, it’s not particularly useful – getting that confirmation after death.

No, it’s not. So, there’s two methods of diagnosis that are currently under trial. The first is PET imaging, which is imaging of the amyloid beta protein. The patient gets injected with a tracer that recognises amyloid beta, which bypasses the blood-brain barrier and, if you’ve got high amyloid beta accumulation, it shows up on the PET scan.

This method is quite costly at about $2,000 per scan and relatively inconvenient as one needs to spend a couple of hours at a hospital. However, it is highly accurate.

The other method being looked at is detecting the amyloid beta in the cerebrospinal fluid (CSF), which is the fluid that surrounds your brain and goes down your spinal cord. The only way we can access this is through a Lumbar puncture (spinal tap) that requires a specialist. The patient has to lie down really still and the specialist draws out one millilitre of it for testing. Although a little cheaper than the PET imaging, this method may make patients feel uncomfortable during the lumbar puncture procedure.

How could your research breakthrough provide an easier method of diagnosis?

Everybody would prefer a blood test. It’s a little bit invasive, but it’s a lot easier to access: we’ve got plenty of blood, most people have a good tolerance for their blood being taken, the medical system already provides numerous blood collection sites, doctors can order a blood test and it’s very simple for the patient to get their blood drawn.

How can the blood test you’ve developed detect the early onset of Alzheimer’s?

Patients typically experience the first sign of symptoms at 65 years old, and those symptoms continue to worsen in the next 1-2 decades. The toxic protein that’s involved in Alzheimer’s disease, amyloid beta, however, starts to accumulate in the brain at around 55 years of age or even earlier.

The disease itself is already happening about ten years before the patient experiences symptoms, and of course patients don’t go to see their doctor until they’re experiencing symptoms. As the load of amyloid beta is already high, researchers believe this may be the reason why it’s difficult to treat the patient as it is too late.

So what we want to be able to do is test early and therefore be able to treat a lot earlier by stopping these amyloid plaques forming or clearing them a lot earlier. We want it to be a cost-effective test, something that can be routine and great for population screening.

How is your research being used beyond Alzheimer’s?

Because of the way we’ve developed the blood test, it can be applied to many diseases, such as Parkinson’s disease and other neurodegenerative diseases. A lot of people internationally and in Australia have contacted us to use this blood test for their disease.

So, we’re looking at using the same technology for melanoma, Malaria, HIV.

Although some of these diseases have diagnostic tests, the technology we use, called Next-Generation deep sequencing, allows us to identify biomarkers of these diseases where we can use them to further understand the pathology of these diseases and assist in therapeutic drug development. Next-generation deep sequencing technology allows you to identify and profile RNA and DNA sequences in samples such as in blood. We’re open to doing this sort of work for other disease.

Lastly, why did you get into this field of research?

I did my PhD in neuronal death and survival. After that I started working for a research and development company overseas where we were developing diagnostic tests. When I came back to Melbourne, I found Andy’s (Professor Andrew Hills) lab, who were getting ready to do this sort of work, so it put both my skills together.

I have a passion for detecting diseases early. I enjoy being able to develop these sorts of things that will have a huge benefit to medicine.

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