Recent biomarker studies of AD (Salloway et al., 2014; Salloway and Sperling, 2015) reported that 36% of ApoE ε4 noncarriers and 6% of ApoE ε4 carriers clinically diagnosed with AD do not have evidence of amyloid deposition and hence do not qualify for the pathologic (true) diagnosis of AD. Here, APOE is linked to Alzheimer disease.