A short report published last week in the Journal of Alzheimer’s Disease claims that a simple saliva test can determine whether or not a person is at risk for developing the incurable neurodegenerative disease by measuring the amount of plaque-forming beta-amyloid protein their body produces. If the levels are high, the authors propose that lifestyle changes, such as taking a daily regimen of anti-inflammatory drugs, can be adopted early in order to postpone the onset of symptoms and reduce disease severity.
Considering that the current methods predicting Alzheimer’s disease (AD) are either unreliable or still experimental, this sounds like great news. On closer inspection, however, it appears that the team may have jumped the gun.
In their much-buzzed-about three-page paper and its accompanying press release, Drs Edith and Patrick McGeer of Aurin Biotech state that in a 2016 investigation they “developed a simple saliva test that can diagnose AD, as well as predict its future onset” by quantifying levels of the Aβ42 protein in the body. Aβ42 is a misproduced protein fragment that accumulates – beginning years to decades before neurological symptoms arise – in the extracellular space of AD patients' brains in clusters called fibrils. These fibrils are toxic to brain tissue.
The initial evaluation of this system proved to be quite promising: AD subjects consistently showed saliva Aβ42 levels that were two-fold higher than controls, as did subjects known to be at a high risk for AD development thanks to family history.
The problem? Their Aβ42 test was only evaluated in 37 people – a pretty small sample size for such bold claims.
“While a simple saliva test for Alzheimer’s sounds appealing, this is very early stage research that needs much more investigation before it could be considered clinically,” Dr Carol Routledge, director of research at Alzheimer’s Research UK, said to the Science Media Centre in response to the new report.