When compared to age‐matched cognitively normal controls, CSF analysis in AD patients exhibits decreased Aβ42/Aβ40 ratio, increased total Tau (t‐Tau) and phosphorylated Tau (p‐Tau) levels, and elevated p‐Tau/Aβ42 ratio (the most accurate CSF diagnostic biomarker combination) [215, 219]. Here, MAPT is linked to Alzheimer disease.