Accurate Blood Test Discriminates Alzheimer's Disease

A pioneering blood test has been identified that may provide a much earlier diagnosis of Alzheimer's disease and other degenerative disorders.

As Alzheimer's disease, the most common form of dementia, is currently only diagnosed with certainty at autopsy, there is considerable interest in finding reliable, noninvasive biomarkers for diagnosis in living people.

Scientists at Saarland University (Homburg, Germany) collaborating with others, focused on the small non-coding ribonucleic acid (RNA) molecules that are known to influence the way genes are expressed, and microRNAs (miRNAs) can be found circulating in bodily fluids, including blood. The team highlighted and tested a “signature” panel of 12 miRNAs among 48 people with Alzheimer's and 22 healthy controls, and discovered different levels in the people with the dementia.

The team carried out high-throughput Next-Generation Sequencing (NGS) of the healthy control and the Alzheimer patient samples using Illumina HiSeq 2000 sequencing (San Diego, CA, USA) with eight multiplexed samples on each sequencing lane. They then developed the tests in a larger cohort of 202 people, comprising not only people with Alzheimer's disease alongside healthy controls, but also patients with other neurological and neurodegenerative disorders. They analyzed the expression of single miRNA using quantitative real time-polymerase chain reaction (RT-qPCR) in the same samples as used for NGS.

The test not only reliably distinguished people with Alzheimer's from the controls with normal health, but also was able to identify other conditions. The results were promising, as they had found useful biomarkers that were 93% accurate, with 95% sensitivity and 92% specificity. The same signature of the 12 miRNAs chosen for their potential to separate Alzheimer's disease from controls, was more than 95% accurate in distinguishing controls from people with various psychiatric disorders, such as schizophrenia, depression and bipolar conditions.

The authors believe accuracy in distinguishing Alzheimer's disease from the wider range of neurodegenerative conditions might be improved by fine-tuning the miRNAs used in the test. They explained that since the 12-miRNA signature has been tailored to differentiate between Alzheimer's disease and controls, other miRNAs may likely contribute to a signature that permits also a better differentiation between the other diseases tested and Alzheimer's disease. The study was published on July 29, 2013, in the journal Genome Biology.

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Saarland University
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