Accumulating research has shown that Chi3l1 levels are greater in patients with early AD (407.81 ± 73.25 ng/mL) than in controls (96.91 ± 11.02 ng/mL) or patients with mild cognitive impairment (MCI; 176.49 ± 25.68 ng/mL), making it a potential biomarker for preclinical AD [152,153,154]. Here, CHI3L1 is linked to Alzheimer disease.