APOE and Alzheimer disease: Therefore, it was decided to classify AD and non-AD patients into ApoE4 non-carriers, ApoE4 heterozygous, and ApoE4 homozygous in order to see differences among the groups (Table 2 and Table 3), as well as correlations between CSF biomarkers and neuropsychological tests in the different subgroups (Table 4 and Table 5).