Therefore, the main aim of our study is to investigate the main p-tau blood biomarkers for AD (p-tau181, p-tau217, p-tau231) together with the other relevant AD-related blood biomarkers (GFAP, NfL, Aβ42/40) in preclinical AD and compare their capacity to indicate Aβ pathology in CU individuals. The gene discussed is GFAP; the disease is Alzheimer disease.