MAPT and Alzheimer disease: Biomarkers that were included were Aβ1–42 and Aβ1–42/Aβ1–40 ratio, which are typically lower in AD patients [13, 16]; Aβ1–40, which is slightly decreased in AD patients in a meta-analysis [13]; sAPPα and sAPPβ, which do not have a clear correlation with AD [13], and T-tau, P-tau181, YKL-40, and hFABP that are all moderately increased in patients [13, 16].