Dementia saliva testing 'shows early promise'

"Simple saliva test for dementia 'shows promise' in bid to diagnose the disease early," the Daily Mirror reports.

This news is based on a laboratory study that took saliva samples from 12 healthy adults, nine adults with Alzheimer’s disease, and eight with mild cognitive impairment (MCI), which is often seen as the stage just before dementia.

Researchers looked at 22 chemical substances (biomarkers) in the saliva, to see if there was a distinct pattern that could indicate whether a person was healthy, had MCI, or had Alzheimer's. They found that a specific chemical make-up of saliva could predict, with a relatively good degree of accuracy, which of these three groups a person fell into.

The findings show promise but this is only preliminary work, as the sample is too small to be conclusive. The next stage is to see if the results can be verified in a much larger sample of people. The researchers calculated that they need ideally at least 100 people in each group.

Where did the story come from?

The study was carried out by researchers from the Beaumont Research Institute and Oakland University William Beaumont School of Medicine in the US, and the University of Alberta in Canada. Funding was provided by the Fred A. and Barbara M. Erb Family Foundation.

The study was published in the peer-reviewed Journal of Alzheimer's Disease.

The Mirror and The Sun's reporting of the study was accurate and appropriately cautious, saying that the test shows promise, without suggesting a test is currently available.

What kind of research was this?

This was a proof-of-concept study. It aimed to see whether it was possible to look at levels of certain substances in saliva to determine whether a person is likely to have mild cognitive impairment (MCI) or Alzheimer's disease.

Alzheimer's is the most common form of dementia, where there is a build-up of characteristic clumps of protein called plaques and tangles in the brain. However, there is no conclusive diagnostic test for Alzheimer's as it can only be diagnosed with certainty by looking at brain tissue after death. A likely diagnosis of Alzheimer's is made on the presence of these characteristic features and by ruling out other causes.

Mild cognitive impairment (MCI), where people start to experience memory problems but fall below the threshold for dementia, can be a preliminary stage to dementia (any type). About 1 in 10 people with MCI progress to dementia each year.

A simple early biological test for Alzheimer's could allow it to be recognised at an early stage, helping people to access the right treatment and to make decisions about their future. Previous studies have already shown it may be possible to distinguish between different types of degenerative brain diseases based on the presence of certain chemical substances, or biomarkers, in body fluids or tissues.

What did the research involve?

The researchers looked at whether there were characteristic chemical differences in saliva samples from healthy people, people with MCI, and people with Alzheimer's.

Saliva samples were collected from 12 healthy adults (controls), eight people with MCI and nine people with Alzheimer's.

All participants were recruited from a centre specialising in care of the elderly. Their diagnoses were made using a variety of tried and tested assessments of brain function (cognitive function), such as the Clinical Dementia Rating Scale, Mini-Mental State Examination and Geriatric Depression Scale.

Saliva samples were analysed using a technique called nuclear magnetic resonance spectroscopy, which allowed the researchers to measure levels of the different biomarkers.

What were the basic results?

The researchers found that the different groups of people could be distinguished with good accuracy based on specific patterns of biomarkers in their saliva.

In particular:

• high levels of acetone and imidazole and low levels of galactose could distinguish people with MCI from healthy controls
• high levels of propionate and acetone could distinguish people with Alzheimer's from healthy controls
• high levels of creatinine and 5-aminopentanoate could distinguish people with Alzheimer's from those with MCI

How did the researchers interpret the results?

The researchers conclude that they have provided "preliminary evidence that salivary metabolites may be useful for [Alzheimer's disease] biomarker development."

They say: "Given the convenience and the frequency with which saliva can be obtained, larger studies are justified."

Conclusion

The researchers are appropriately cautious in their conclusions. These findings have potential, but this is an early stage pilot – a starting point for further study.

The tests were carried out in small samples of healthy people and those with cognitive impairment. They would have to be validated in much larger groups, in which it's possible the test would give different findings. The researchers calculate that they would need at least 100 people per group to develop models that could reliably detect significant differences in biomarkers between the groups.

Even among this small sample, we don't know from the information provided that the people definitely had Alzheimer's disease. They were assessed using a range of cognitive assessments, but we don't know other aspects such as their medical history and results of brain imaging. It's possible, for example, that some of these people could have had vascular dementia.

Even if further research finds a profile of biomarkers that is reliable enough at identifying people with MCI or Alzheimer's, there would still be many more considerations before introducing this as a screening test. For example, who should be screened and would testing offer any benefit over current diagnostic methods based on clinic assessment?

Currently, though there are drugs that can be prescribed for people with mild to moderate dementia, there is no treatment that can prevent or cure dementia. Therefore earlier recognition at this stage would help people get the support they need, but is unlikely to change the course of the disease. This may change if there are future drug developments.

Current advice stands, that if you or a family member or friend are having problems with memory and understanding, it's important to contact a health professional to get the support needed. Memory and cognitive problems can have a wide range of causes so it would be unwise to assume that they are a sign of dementia.

For more information visit the NHS Choices dementia guide.