Since the clinical manifestation of AD neuropathology is hypothesized to progress through the presymptomatic, MCI, and dementia stages, we next examined in this cross-sectional cohort whether levels of the candidate analytes differed among NC–, NC+, MCI+, and AD dementia through ANCOVA adjusting for age, sex, education, and presence of APOE ε4 allele. The gene discussed is APOE; the disease is Alzheimer disease.