MAPT and tauopathy: To date, a number of studies have evaluated the relationship between CSF AD biomarkers and amyloid PET imaging, and found a strong correlation between the signal of amyloid PET ligands and the levels of CSF Aβ42, especially the ratio of Aβ42 with other AD biomarkers (e.g., t‐Tau/Aβ42, p‐Tau181/Aβ42, or Aβ42/Aβ40),10, 18, 19, 21, 22, 23 although t‐Tau/Aβ42 or p‐Tau181/Aβ42 ratios might lead to false positives because t‐Tau or p‐Tau181 could be upregulated by non‐AD tauopathies.24, 25