CHI3L1 and Alzheimer disease: Elevated YKL-40 levels have been consistently reported in the cerebrospinal fluid (CSF) and plasma of individuals with AD, correlating with tau pathology, neuronal injury, and clinical progression (Bonneh-Barkay et al., 2010; Kester et al., 2015; Llorens et al., 2017; Pase et al., 2024).