Key points from article :
A blood test could spot Alzheimer's disease at the earliest stage pre-symptoms.
The test looks for tiny amounts of a protein which is elevated in people with the illness.
Measuring the protein, p-tau217, could predict Alzheimer's dementia with 96% accuracy.
Though clinical trials still far, it will now be available for research purposes.
US team observed p-tau217 elevated levels in as little as 4mL of blood.
They have shown it could be detected in brain and spinal cord fluid pre-symptoms.
Another research found Alzheimer's patients had about 7 times of this protein as without Alzheimer's.
It could also distinguish them from people with other degenerative brain conditions.
Separate research from Washington University School of Medicine and Lund University.