CHI3L1 and Alzheimer disease: Additionally, serum concentrations of YKL-40 can effectively distinguish between CU individuals and those with mild dementia, with a sensitivity and specificity of 85% [164], although it is not clinically useful in differentiating the characteristic AD phenotype and increased YKL-40 concentrations in CSF or plasma have been found in various age-related pathological conditions, posing a constraint on its future application as a biomarker in the older population [84].