APOE and Alzheimer disease: Limited studies have demonstrated that the number of APOE ε4 alleles was not associated with plasma Amyloid β (Aβ) 40, Aβ42, Aβ42/Aβ40, and phosphorylated tau (P-tau)181 for AD patients (Janelidze et al., 2016; Salami et al., 2022).