By the Blouin News Science & Health staff

A putative diagnostic blood test for dementia and Alzheimer’s disease

by in Medicine, Research.

 British Prime Minister David Cameron (C) speaks with representatives of Alzheimer's Society Dementia Friends during an information session in Downing Street. Getty/ Facundo Arrizabalaga

British Prime Minister David Cameron (C) speaks with representatives of Alzheimer’s Society Dementia Friends during an information session in Downing Street. Getty/ Facundo Arrizabalaga

Researchers at Saarland University in Hamburg, Germany developed a method to differentiate healthy individuals from those with dementia, as well as from those with milder brain diseases such as Alzheimer’s, Parkinson or schizophrenia. The study published in the journal Genome Biology, identified 12 molecules (called microRNAs) that circulate in the blood and can be used as a diagnostic tool to detect dementia, and perhaps other neurodegenerative diseases, long before the symptoms begin.

Dementia is the gradual decline of the function and agility of the brain which brings memory loss, language impairment, and inability to focus and reason. It affects the everyday life of millions of people (about 14% of all individuals above 71 years of age – about 3.4 million – according to an epidemiological study). It is caused by brain diseases, the most common being Alzheimer’s disease. In dementia, neurons in the brain cannot function properly and it becomes hard for brain cells to communicate and process stimuli from the environment.

Until now, no test could tell if someone has dementia. Doctors diagnose dementia after assessing cognitive abilities, medical history and familial background, and results of clinical examinations mainly performed to rule out other diseases. As the elderly population increases, scientists look for a test to diagnose dementia, or the brain diseases that lead to it, to help the individuals improve the quality of everyday life before the first symptoms arise.

Working towards this goal, a team of researchers led by Eckart Meese and Andreas Keller at the Department of Human Genetics, Saarland University, Homburg, Germany, obtained blood samples from a biorepository and performed next generation sequencing, a very sensitive technique that detects DNA and RNA even at very low levels. They have compared the microRNAs (miRNAs – RNA molecules which regulate the expression of genes) of healthy controls or Alzheimer’s disease (AD) patients and found about 140 miRNAs that had increased or decreased levels. They focused on 12 that were relevant to the proper development of neurons and the nervous system. They tested whether these 12 miRNAs can differentiate blood samples of healthy, AD patients or patients of other neurological diseases (multiple sclerosis, Parkinson’s, bipolar disorders etc) which subsequently lead to AD and dementia, as an effort to measure the transitional period from healthy to AD.

The result was great; the researchers could differentiate with the highest accuracy and specificity not only the controls from the AD, but also the AD from the milder neurological diseases. The differentiation of the middle-staged patients from the healthy was also very accurate, suggesting that the panel of the 12 miRNAs can become a good indicator of the progress of AD.

The biggest advantage is that this can be used simply as a blood test with minute amount of sample.Until now, the only way to confirm and identify the exact type of dementia has been a post-mortem brain autopsy. Available tests are not as sensitive or accurate and require the measurement of molecules in the cerebrospinal fluid, a fluid which flows in the brain to protect the brain from damage but it is difficult to obtain. However, the authors acknowledge that additional work is required before it can be implemented as a diagnostic tool for dementia, and it remains to be seen whether it will become applicable.