CHI3L1 and Alzheimer disease: CSF was collected at shunt insertion and postoperatively by shunt reservoir puncture, and analyzed for concentrations of GFAP, YKL40, MCP-1, NfL, Aβ40, sAβPPα, sAβPPβ, GAP43, Alzheimer's disease biomarkers Aβ42, Aβ42/40, total tau (T-tau), phosphorylated tau (P-tau), and neurogranin.