CHI3L1 and Alzheimer disease: Then, we summarize published data on the frequently used compounds (biomarkers) in AD research, namely Aβ1-40, Aβ1-42, hyperphosphorylated tau (P-tau), T-tau, neurogranin, SNAP-25, glial fibrillary acidic protein (GFAP), YKL-40, and neurofilament light (NfL), and their presence/concentrations in brain and body fluids (blood/serum/plasma and CSF) in human AD subjects and controls and in frequently used animal models of AD.