APP and Alzheimer disease: Consistent with the well-characterized neuropathology of AD and studies utilizing pTau and AβPP-Aβ CSF-based biomarker assays to diagnose or monitor AD [59–61], we detected increased levels of pTau and AβPP-Aβ in postmortem brains that had intermediate (Braak 3–4) or advanced (Braak 6) stages of AD.