CHI3L1 and Alzheimer disease: The CSF levels of YKL-40 (ng/ml) in lvPPA, LOAD, EOAD, and PCA were significantly higher than those in ND (p < 0.0001, p < 0.0001, p < 0.001, p = 0.044, respectively); meanwhile no significant difference was noted among the four AD subtypes (Kruskal-Willis-test: p = 0.148; Table 5).