Where do we stand on the relationship between tau biomarkers and mild cognitive impairment?

We present an editorial on a recent publication by Amlien et al. [2013] in which diffusion tensor imaging (DTI) was used to quantify longitudinal decreases in fractional anisotropy (FA) and increased radial diffusivity (DR) in patients with mild cognitive impairment (MCI). These longitudinal alterations were found to be greater in MCI patients with high cerebrospinal fluid (CSF) tau levels at baseline and greater than healthy controls. Amlien et al. concluded that tau levels were an important early biomarker for predicting rate of disease progression and outcome. The results of this study are an interesting finding for possible predictive use of tau levels in MCI. However, in our assessment, the methodology does not support the conclusion that CSF total tau levels are predictive of MCI progression towards a disease state such as Alzheimer's disease (AD). Further longitudinal study is needed, that includes follow-up neuropsychological assessment and conversion of subjects in the study to AD, to conclude that CSF total tau levels represent a predictive biomarker of MCI progression towards AD.