MAPT and Mental deterioration: Our finding of higher specificity for [18F]RO948 than for CSF Aβ42/Aβ40, when distinguishing AD dementia from no cognitive impairment and non-AD diseases, is consistent with this study and earlier findings that tau PET positivity is associated with the onset of cognitive decline and dementia.51 Together, these findings appear to support the notion that tau PET is a valuable addition to Aβ biomarkers in the workup of early-onset dementia and as a stand-alone test in patients with late-onset dementia where Aβ pathology is frequent.