CSF phosphorylated tau--does it constitute an accurate biological test for Alzheimer's disease?

Abstract

Introduction: There is considerable interest in developing a diagnostic test which could differentiate between early Alzheimer's disease (AD) and other causes of memory impairment with more than 80% sensitivity and 80% specificity.

Objective: To review the studies that have examined CSF phosphorylated tau as diagnostic test of AD vs clinically representative comparison groups.

Method: A critical review of the literature using Embase, Web of Science, Medline and Psychinfo databases supplemented by handsearching and contact with experts in the field.

Results: CSF phosphorylated tau is a marker of AD that improves upon the utility of CSF total tau and clinical examination alone. Studies have found high levels of tau phosphorylated at Threonine 231 and/or Serine 199 in AD but not in other causes of dementia, in depression or in healthy elderly controls. Of particular interest, the test appears equally valid in cases of early AD as in moderate or late stages and may also be of use in predicting future decline in subjects with mild cognitive impairment.

Conclusion: CSF phosphorylated tau is a promising diagnostic test for AD but this requires replication using pathologically confirmed cases.