A/T/N Classification
| Classification | Description |
|---|---|
| A (amyloid) | Decreased CSF Aβ42 or Aβ42/Aβ40 ratio or positive amyloid PET |
| T (tau) | Increased CSF phosphorylated tau or positive tau PET |
| N (neurodegeneration) | Atrophy on structural MRI or decreased uptake on 18F-FDG PET or increased CSF total tau |
Amyloid and tau are considered defining biomarkers of AD. Neurodegeneration is used to stage severity of disease (independently from AD pathology).