MAPT and Alzheimer disease: Peripheral blood biomarkers associated with AD can be identified before the formal diagnosis.22,23 Blood biomarkers correlate with changes in cognition and brain atrophy and could be used to inform treatment implementation and management in clinical practice.24 The accumulation of amyloid beta (Aβ) peptides, which are often found in extracellular plaques and intracellular neurofibrillary tangles that compromise the tau protein, is the defining criterion of AD.