Tau protein in cerebrospinal fluid: A new diagnostic and prognostic markerin Alzheimer disease?

Tau is the main protein of paired helical filaments. It can be detected and measured in cerebrospinal fluid (CSF) and for this reason it has been prop osed as a possible in vivo marker of Alzheimer disease (AD). To evaluate th e usefulness of CSF tau in the diagnosis of AD we measured it in patients w ith AD, frontal lobe dementia (FLD), vascular dementia (VD), and in healthy controls by means of a specific enzyme-linked immunosorbent assay test. In dividuals with AD had significantly higher tau levels than FLD, VD, and con trols. Individuals with late onset AD had significantly higher levels than those with early onset disease. In AD, CSF tau level did not correlate with age, duration, or severity of the disease, whereas a correlation with age was found in FLD and controls. In the nine AD patients in whom CSF tan meas urement was repeated after 2 years, mean levels did not differ from baselin e, although a worsening of cognitive performances occurred. The overlap amo ng the different groups and the absence of any modification over time sugge st that CSF tau measurement, more than in confirming or staging overt AD, m ight be useful in revealing the disease at its preclinical phase.