Some progress toward a simple saliva test for Alzheimer's disease

Two recent pilot studies give some hope that it may be possible to develop a simple test for Alzheimer’s disease or possibly even to detect those who are going on to develop the disease later. 

The first study is from researchers in Canada. These researchers have developed a test for detecting levels of amyloid β42 (Aβ42) which is a small peptide and part of the amyloid-β protein precursor. They measured this peptide in saliva in a very small sample of people with Alzheimer’s and healthy controls. One of the controls had a gene mutation that predisposes to later development of Alzheimer’s. Levels of Aβ42 were higher in people with Alzheimer’s and also in those at risk of developing the disease because of family history or having a predisposing mutation.

The second study by researchers from Chicago used a different approach. They used a screening method called magnetic resonance spectroscopy to measure a large number of small chemical substances (metabolites) in saliva from people with Alzheimer’s disease, a group with mild cognitive impairment and some healthy controls. They looked at patterns of metabolites in the three groups of people and found that in each case they could identify which group they belonged to by differences in the levels of just two or three different metabolites in each case.

Both these studies are encouraging in that they suggest that it may be possible to diagnose Alzheimer’s disease early. However both of these are just pilot studies on very small numbers of patients. They will need to be replicated using much larger samples of people with a variety of conditions to show that these tests still work under these circumstances. As we have pointed out many times previously, encouraging test results in small scale pilot studies often disappoint when they are tried in large groups of subjects under real-world conditions.
 
Further Reading
Women’s Brain Health Initiative – Saliva Test for Alzheimer’s?
PubMed Health - Dementia saliva testing 'shows early promise' 



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