Blood test boosts hopes of early Alzheimer’s diagnosis

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A commercially available blood test has shown high levels of accuracy in detecting Alzheimer’s, even in its early stages, boosting the prospects of early diagnosis for sufferers of the neurodegenerative disease.

Alzheimer’s, a type of dementia, is currently diagnosed through invasive and expensive tests such as a lumbar puncture to release spinal fluid or through a tomographic scan. Patients can face long waits for these procedures.

But according to a peer-reviewed study by Sweden’s Gothenburg university, a blood test known as the p-tau217 immunoassay yielded “high accuracy” in identifying tau, one of the proteins associated with a toxic build-up in the brain that can cause Alzheimer’s, across all 786 patients in the trial.

The results, published in the JAMA Neurology journal on Monday, were “comparable with [those] using cerebrospinal fluid biomarkers”, with reproducible results even when Alzheimer’s was in its early stages, the researchers wrote.

“The hope is that blood tests like this will improve access to a diagnosis in those seeking help for memory problems, and ultimately ensure that people can benefit from emerging treatments that can slow the progression of Alzheimer’s disease,” said Charles Marshall, a professor of clinical neurology at Queen Mary University of London, who was not involved in the test.

But he cautioned that further evidence was needed to “show that the blood test can accurately diagnose who is in the process of developing dementia, and that it can identify who is likely to benefit from treatments to slow down the disease” before it could be widely rolled out.

Richard Oakley, associate director of research and innovation at the UK’s Alzheimer’s Society, said the study was a “hugely welcome step in the right direction” because it appeared to be as accurate as the invasive and expensive tests, suggesting some patients would not need follow-up tests to confirm the blood test’s findings.

Lumbar punctures and tomography scans for Alzheimer’s are only available in about one out of 20 memory clinics in the UK’s NHS, Marshall said.

Oakley said there were “potentially groundbreaking new drugs” that could slow the progression of early-stage Alzheimer’s. But patients would need “an early, accurate diagnosis” to be eligible for them if the products were approved by global regulators, he added.

Drugs made by Japan’s Eisai and Eli Lilly of the US have shown promise when used early in an individual’s development of the disease. Both drugs were also shown to be effective in slowing down the disease’s progression.

But there have been numerous setbacks in the field, even with drugs that were approved by US regulators and never widely adopted because of safety and efficacy concerns.

According to the World Health Organization, more than 55mn people globally are estimated to have dementia, with 60 per cent living in poorer countries. There are 10mn new cases recorded each year.

Alzheimer’s is estimated to contribute to 60-70 per cent of the global dementia caseload.