Last year I reported on a finding that ten lipids in the blood could predict development of MCI or Alzheimer's within 2-3 years, with over 90% accuracy. The hunt for an accurate blood test has been gathering momentum, on the back of the growing belief that any effective treatment of Alzheimer's might have to start early, and the high cost and inconvenience of other means of early diagnosis.
Since that report we have had several more findings. Bear in mind that 90% accuracy still means one in 10 people would get an incorrect result.
Blood proteins predict whether MCI will convert to Alzheimer's with 87% accuracy
Blood from 452 healthy people, 220 people with mild cognitive impairment, and 476 with Alzheimer’s disease, has allowed researchers to identify those whose MCI would progress to Alzheimer's. The study identified 16 proteins that were associated with brain shrinkage in MCI or Alzheimer's. Further testing revealed 10 proteins that could predict, with 87% accuracy, whether MCI would progress to Alzheimer's within the next 12 months.
Blood microRNA predicts Alzheimer's disease
A preliminary study using serum from 49 Australians has found that microRNA in the blood can predict early changes in the brain that are associated with Alzheimer's.
One in five healthy participants with no memory complaints showed the specific microRNA associated with Alzheimer's. Brain imaging then confirmed the presence of early degeneration. The 16-miRNA signature, together with established risk factors such as age, sex and apolipoprotein ε4 gene status, predicted Alzheimer's with 91% accuracy.
Large Danish study links ApoE in blood to Alzheimer's risk
A study using data from nearly 76,000 Danes has shown that the level of the biomarker apolipoprotein E in the blood can predict the risk of developing dementia, with low levels being associated with a higher risk. Apolipoprotein E in the brain is strongly associated with Alzheimer's, with the ApoE4 gene the strongest genetic factor linked to Alzheimer's risk.
The study found that the link between blood plasma level and Alzheimer's and dementia risk existed irrespective of APOE genotype.
 Plasma proteins predict conversion to dementia from prodromal disease. Alzheimer's & Dementia: The Journal of the Alzheimer's Association [Internet]. 2014 ;10(6):799 - 807.e2. Available from: http://www.alzheimersanddementia.com/article/S1552526014024546/abstract
 Prognostic serum miRNA biomarkers associated with Alzheimer’s disease shows concordance with neuropsychological and neuroimaging assessment. Molecular Psychiatry [Internet]. 2014 . Available from: http://www.nature.com/mp/journal/vaop/ncurrent/abs/mp2014127a.html
 . Plasma levels of apolipoprotein E and risk of dementia in the general population. Annals of Neurology [Internet]. 2015 ;77(2):301 - 311. Available from: http://onlinelibrary.wiley.com/doi/10.1002/ana.24326/abstract