Abstract
This commentary focuses on the clinical utility of plasma amyloid-β (Aβ) 42/40 to detect semantic intrusion errors in amnestic mild cognitive impairment, as investigated Curiel Cid et al. in a recent issue of the Journal of Alzheimer's Disease. This commentary highlights the importance of testing the sensitivity of plasma Aβ(42/40) to clinical symptoms in the quest to develop a comprehensive definition of AD that incorporates both biological precursors and clinical consequences.