MAPT and Alzheimer disease: Studies have explored the potential ofthe amyloid-β 1-42 and amyloid-β 1-40 peptides as biological markercandidates of AD with conflicting results, showing their ability or otherwise todiscriminate AD patients from healthy controls.5,6 Some evidencesuggests that a steady fall in plasma amyloid-β peptides is associated withprogressive cognitive decline in the course of AD but further studies are needed tocorrelate these findings.7 Thus,unlike the assessment of tau protein or amyloid-β peptides in CSF, serum orplasma, levels of these molecules appear to have little clinical value.