Laboratory diagnostic tests for Alzheimer's disease.

Alzheimer disease/senile dementia of the Alzheimer type (AD/SDAT) is a neuro-degenerative disease which is characterized by the accumulation of paired helical filaments (PHF) in the form of neurofibrillary tangles and neuritic (senile) plaques in the brain. The clinical diagnosis of AD/SDAT is made by excluding other causes of dementia and is uncertain in 10-50% of the cases. The histopathological diagnosis of AD/SDAT can be made only on brain biopsy or after the patient has died on autopsied brain. Presently no laboratory diagnostic test for AD/SDAT is available. Employing a monoclonal antibody to PHF, CSF from clinically diagnosed AD/SDAT and a control group of non-AD/SDAT living patients were probed by a competitive ELISA (enzyme linked immunosorbent assay). The PHF immunoreactivity was found higher in AD/SDAT as compared to control cases suggesting that a laboratory diagnostic test based on this assay might be feasible. Screening of a large number of cases, especially with histopathological confirmation, at multiple AD/SDAT medical centers must be carried out to evaluate the specificity and the sensitivity of the test.