MAPT and Alzheimer disease: This umbrella review synthesises evidence from systematic reviews examining diagnostic blood-based biomarkers (BBMs) predictive of amyloid-β and tau pathologies prior to clinical AD diagnosis.<h4>Methods</h4>We conducted an umbrella review of systematic reviews published between 2018 and 2024, selecting those that synthesised data on BBMs associated with amyloid-β or tau pathologies in adults in preclinical or prodromal AD stages.