Scientists have taken a step toward developing a blood test for Alzheimer's, finding a group of markers that hold up in statistical analyses in three independent groups of patients.
US researchers measured the levels of 190 proteins in the blood of 600 study participants, included healthy volunteers and those who had been diagnosed with Alzheimer's disease or mild cognitive impairment (MCI).
The results, to be published in the August 28 issue of the journal Neurology, showed that levels of 17 of the 190 protein were significantly different in people with MCI or Alzheimer's. When these markers were checked against data from 566 people participating in the multicenter Alzheimer's Disease Neuroimaging Initiative, only four markers remained: apolipoprotein E, B-type natriuretic peptide, C-reactive protein and pancreatic polypeptide.
Changes in levels of these four proteins in blood also correlated with measurements from the same patients of the levels of proteins [beta-amyloid] in cerebrospinal fluid that previously have been connected with Alzheimer's. The analysis grouped together people with MCI, who are at high risk of developing Alzheimer's, and full Alzheimer's.
William Hu, assistant professor of neurology at Emory University School of Medicine, said: “Reliability and failure to replicate initial results have been the biggest challenge in this field. We demonstrate here that it is possible to show consistent findings.
“MCI has been hypothesised to be an early phase of AD, and sensitive markers that capture the physiological changes in both MCI and AD would be most helpful clinically.
"The specificity of this panel still needs to be determined, since only a small number of patients with non-AD dementias were included. In addition, the differing proportions of patients with MCI in each group make it more difficult to identify MCI- or AD-specific changes."
W.T. Hu et al. Plasma multianalyte profiling in mild cognitive impairment and Alzheimer disease. Neurology 79, 897-905 (2012)