A blood test that finds abnormally high levels of a tau protein can distinguish dementia due to Alzheimer’s disease from frontotemporal lobar degeneration, according to a study published in Nature Medicine and reported on in Neurology Today. In a second study from the same issue of the journal, the blood test was also able to predict which patients who were cognitively normal or had mild impairment would go on to develop Alzheimer’s dementia.

A blood test for Alzheimer’s disease (AD) pathology appears to be as accurate as more invasive measures and equally well correlated with AD dementia, according to two studies published simultaneously in the March issue of Nature Medicine.

The studies measured plasma phosphorylated-tau-181 (p-tau181), a form of the tau protein, and found that abnormally high levels are as closely linked to dementia due to AD as are PET scans of amyloid protein and measures of p-tau181 in cerebrospinal fluid.

Not only did a high level of plasma p-tau181 distinguish AD from frontotemporal lobar degeneration, but in one of the studies it also predicted which patients who were cognitively normal or had mild cognitive impairment (MCI) upon initial evaluation would later develop Alzheimer’s dementia.

Read more from Neurology Today and find study 1 and study 2 in Nature Medicine.