APOE and amyloidosis: Our analyses on the interaction between Aβ42 with APOE4 genotype on CSF tau levels may suggest that molecular processes associated with amyloid pathology “override” the effects of APOE4 on CSF tau levels in amyloid-positive subjects; thus, a significant independent effect of APOE4 genotype on CSF tau can only be demonstrated in amyloid-negative subjects.