LONDON - Scientists have moved a step closer to developing a blood test that can predict whether people are at risk of Alzheimer’s, reports The Times.

The disease has long been associated with the build-up of a protein called amyloid in the brain, but although everyone with Alzheimer’s has these amyloid plaques, not everyone with the plaques gets Alzheimer’s, suggesting that something else is involved.

Now, researchers have identified what that might be: a star-shaped cell called an astrocyte. For their study, they gave 1,000 people in their 60s and 70s blood tests and PET scans to gauge their amyloid levels, and also tested for astrocyte reactivity.

They found that the patients with abnormal astrocyte activity were the ones whose amyloid levels continued to build up, and triggered the activation of another protein, called tau, that is also closely associated with Alzheimer’s. “This puts astrocytes at the centre as key regulators of disease progression,” said Dr Tharick Pascoal, of the University of Pittsburgh.

The hope is that it will now be possible to develop a combined test for Alzheimer’s, which would lead to much earlier diagnoses, and perhaps new treatments.