APOE and Alzheimer disease: The apparent inconsistencies in the published literature on ApoE levels in AD or MCI may be due to multiple differences between studies, including; (1) the sample, which can be CSF, serum, plasma, urine or tissue (2) experimental design (i.e., cross-sectional or longitudinal), (3) subject numbers, which can vary from a handful of individuals to many 100’s if not 1000’s of subjects, (4) methodological differences in the assay procedure which may affect sensitivity or recovery.