ACHE and Alzheimer disease: Results of classical spectrophotometric studies of AChE in AD serum or of the enzyme in plasma have been contradictory and vary widely in activity from very low values (6–12 mU/mL), similar to values reported from immunoassays [15], [16], [47], to 10–50 times higher (60–300 mU/mL) [17], [18], to values similar to that observed for BuChE (∼2000 mU/mL) [19], [48].