CHI3L1 and early-onset autosomal dominant Alzheimer disease: For example, CSF levels of YKL‐40 have been previously reported to be increased in Alzheimer's disease, peaking at the prodromal stage (Gispert et al, 2016a), similarly to what has been described for CSF sTREM2 (Suarez‐Calvet et al, 2016b).