Alzheimer's Disease - diagnose by blood test?

The diagnosis of Alzheimer's Disease is made by carrying out neuropsychological tests that measure memory, language skills and other brain functions, and by the exclusion of other causes of dementia, sometimes using brain scans. A definitive diagnosis can only be made at post-mortem. Some changes in the proteins in cerebrospinal fluid (CSF) have been identified, but the collection of the fluid is difficult and not without risk.

A successful search for protein abnormalities in the blood plasma of patients with Alzheimer's Disease was reported by Professor Simon Lovestone and 19 colleagues from King's College London in the November issue of the journal Brain. They separated individual plasma proteins by a method depending on both the electrical charge and the size of the molecules (two dimensional gel electrophoresis). Blood proteins that were present in concentrations in Alzheimer's patients that differed from those in other forms of dementia and normal elderly people were then removed and identified by a complex analytical process (liquid chromatography mass spectrometry). Identification of the individual proteins was confirmed using immunological techniques.

Two proteins previously shown to be present in the brain lesions of Alzheimer's, complement factor H precursor and alpha-2 macroglobulin, showed the greatest increase in Alzheimer's patients. These two proteins were then measured in blood plasma by a widely available lab technique, the Western Blot. Unfortunately the results by this method were not specific or sensitive enough for the test to be used to diagnose or monitor Alzheimer's Disease.

Professor Lovestone said: "This is certainly an exciting development in the battle against Alzheimer's. It is a devastating disease and we currently have problems diagnosing it and measuring its progression in patients. Further research is now needed to establish if a simple, accurate blood test for Alzheimer's can become a reality."