There is a long presymptomatic period during which a person may have
biomarker evidence of Alzheimer’s disease (AD) pathophysiology but still
be cognitively intact. It is yet unclear which additional factors that
ultimately will determine progression to mild cognitive impairment and
eventually to AD dementia. Amyloid-β (Aβ) and tau imaging reveal in vivo
the key protein aggregates seen in the AD brain and will help in early
diagnosis. However, a considerable proportion of elderly individuals are
Aβ PET positive while being cognitively intact. With FDG PET, a typical
pattern of hypometabolism can be found in both AD and FTD, which
reflects the disease progression and can be used to aid in the
differential diagnostics. Moreover, tau, neurotransmitter, and
neuroinflammation ligands help to understand the pathophysiology of AD,
but further studies are needed to understand how they can be applied in
the diagnostic process. Which combination of these biomarkers that
eventually will turn out to be the most sensitive and best predictor of
AD remains to be determined.