GFAP and Alzheimer disease: Single‐center biomarker studies including different dementia types showed that Aβ42/40 was decreased only in those with Aβ pathology; p‐tau181 was increased mainly in those with AD, but increases during preclinical AD (preAD) and mild cognitive impairment (MCI) prior to clinical AD dementia; GFAP, defined as a marker of Aβ‐related astrocyte reactivity in autosomal dominant AD11 was increased in all dementias compared to controls;12, 13 and NfL had the highest values/concentrations in patients with FTD.