Draft new proposed international guidelines hold promise of hope

Doctors could soon use blood tests to detect signs of Alzheimer’s in the brain in a move described by Australian experts as a sensible approach.

Blood tests and brain scans may soon replace memory tests for earlier and more accurate diagnosis of Alzheimer’s disease in a move set to revolutionise treatment.

Alzheimer’s disease is the most common cause of dementia, with around 50,000 new cases diagnosed in Australia every year.

This week a draft proposal for new diagnostic criteria was presented at the Alzheimer’s Association international conference in the Netherlands. It is now under consideration and open for a 30-day public consultation.

The proposed criteria was developed on behalf of the Association and the American National Institute on Aging as a revision of 2018 guidelines.

While Australian experts describe the new approach as sensible, they caution that it will also require access to some tests that are not yet widely available here.

University of Melbourne’s Professor Chris Rowe, who is also the director of the Australian Dementia Network, says while aspirational, for now the draft criteria would largely be applied in research and trials in Australia.

“That will change over the next few years as the new blood tests get into the market,” Prof Rowe said.

Australian Dementia Network director Professor Chris Rowe. Picture: Hamish Blair

The conference was told the revision was necessary because of “significant advances” including regulatory approval for targeted therapies and the development of excellent diagnostic blood biomarkers, some of which have been clinically proven.

They call for Alzheimer’s to be defined biologically rather than on clinical symptoms and highlight that early diagnosis will help people understand the cause of their cognitive challenges so they can make informed decisions about how they want to manage their lives.

It would also mean for the first time doctors will be directed to consider using blood tests first to detect signs of Alzheimer’s in the brain.

These blood biomarker tests look for proteins known as beta-amyloid and tau along with other signals considered telltale signs of the disease.

Associate Professor Paul Yates is a geriatrician and researcher at Austin Health and the University of Melbourne who was the lead investigator on a major study of Lecanemab in Australia. This is the drug that has recently been approved as a targeted therapy for Alzheimer’s in the US and is now being assessed by the TGA in Australia.

He says some important system changes would be required in Australia to support the suggested criteria into daily practice once the consultation process was complete and approved, but added the potential was exciting.

“In the past, a diagnosis of dementia was largely a clinical diagnosis, based on symptoms of memory or thinking decline that were serious enough to affect someone’s ability to live independently day-to-day,” Professor Yates said.

He said it was now possible to measure evidence of Alzheimer’s through the underlying proteins beta-amyloid and abnormal forms of tau protein using PET scans, cerebrospinal fluid tests, and now blood tests.

Associate Professor Yates says new drug therapies are only part of the management of dementia, and that lifestyle, diet, social and carer support factors are also of critical importance.

Julie Stout, a professor in the School of Psychological Sciences at Monash University, said the draft guidelines also presented a welcome opportunity for other progressive degenerative brain diseases where biological changes occurred before the clinical symptoms presented.

“If the blood tests tells us we are high risk, then there is also the opportunity to look at what lifestyle changes we could we make to delay the effects of the biology on our function,” she said.