People suffering from the most common form of dementia, Alzheimer’s disease, may be able to detect it early with a new blood test, a new scientific study found.

The study, published in JAMA and undertaken by scientists at Lund University, found that a combined blood test for cognitive decline had a 90 per cent accuracy rate in determining if the cause was Alzheimer’s disease.

Dr Oskar Hansson, a professor of clinical memory research at Lund University, said because the pathology and biomarkers of Alzheimer’s disease can start to develop 20 years before any symptoms, there is a “risk of anxiety and other reactions, psychological reactions, to such a test result”.

“If you would detect Alzheimer’s disease pathology in the person without cognitive impairment, there are no therapies to offer,” he told The New York Times.

“We advocate strongly that patients should still undergo the standard of care of today in both specialist care and primary care.”

The tests had a higher success rate than when compared to the 73 per cent accuracy for neurologists and related specialists, and 61 per cent for doctors when determining if the memory loss was because of Alzheimer’s disease without the use of PET scans or spinal taps.

Alzheimer’s disease is the most common form of dementia, with an estimated total of more than 400,000 Australians suffering from it in 2024.

How it works

The blood test works by measuring the tau protein 217, which scientists have found to be one of the biomarkers for diagnosing early-stage Alzheimer’s and cognitive impairment.

Dr Sebastian Palmqvist, an associate professor and senior consultant neurologist at Lund University in Sweden, told CNN that because tau protein 217 increases at the same rate as other damaging proteins in the brain of people with Alzheimer’s, it is an excellent indicator of amyloid pathology.

“Increases in p tau-217 concentrations in the blood are quite profound in Alzheimer’s disease,” he said.

“At the dementia stage of the disease, levels are more than eight times higher compared with elderly without Alzheimer’s.”

The blood test gives a more accurate chance of diagnosis without being an invasive procedure. Photo: Getty

The study recorded the results of 1213 people, with an average age of 74, who were undergoing cognitive testing at primary care and specialist clinics.

Diagnosing Alzheimer’s

The accuracy of the blood test was verified with spinal fluid taps, which are commonly used alongside amyloid PET scans as the soundest method for diagnosing Alzheimer’s in a live person, although both are invasive and expensive.

Currently, most doctors will use an interview with a patient, a cognitive test and a CT scan of the brain to diagnose Alzheimer’s.

Studies have found that other diseases and medications can mimic the appearance of Alzheimer’s and dementia in patients, making it difficult for doctors and specialists to diagnose correctly.

Patients with “prominent language impairment; and those with behavioural and psychiatric changes” are often misdiagnosed because their neurological signs of impairment may not be as visible or may be hidden.

On average, people live between three and 11 years after diagnosis.

There is currently no cure to Alzheimer’s disease, although some drugs have shown promising results in slowing the progress of it.