Scientists have developed a blood test to diagnose Alzheimer's disease without the need for expensive brain imaging or a painful lumbar puncture, where a sample of cerebrospinal fluid (CSF) is drawn from the lower back. If validated, the test could enable faster diagnosis of the disease, meaning therapies could be initiated earlier. The Guardian reports:Current guidelines recommend detection of three distinct markers: abnormal accumulations of amyloid and tau proteins, as well as neurodegeneration -- the slow and progressive loss of neuronal cells in specified regions of the brain. This can be done through a combination of brain imaging and CSF analysis. However, a lumbar puncture can be painful and people may experience headaches or back pain after the procedure, while brain imaging is expensive and takes a long time to schedule.

Although current blood tests can accurately detect abnormalities in amyloid and tau proteins, detecting markers of nerve cell damage that are specific to the brain has been harder. [Prof Thomas Karikari at the University of Pittsburgh, in Pennsylvania] and his colleagues around the world focused on developing an antibody-based blood test that would detect a particular form of tau protein called brain-derived tau, which is specific to Alzheimer's disease. They tested it in 600 patients at various stages of Alzheimer's and found that levels of the protein correlated well with levels of tau in the CSF, and could reliably distinguish Alzheimer's from other neurodegenerative diseases. Protein levels also closely corresponded with the severity of amyloid plaques and tau tangles in brain tissue from people who had died with Alzheimer's.

The research was published in the journal Brain. (Warning: That study has been published in the usual medical terminology. It is intended to be read by medical professionals, not everyday common folks.)