Cerebrospinal fluid (CSF) amyloid beta 38 (Aβ38), amyloid beta 40 (Aβ40), amyloid beta 42 (Aβ42) and total tau (T-tau) are protein biomarkers used in the clinical diagnosis and research analysis of, and drug development for, Alzheimer’s disease (AD). This evidence concerns the gene MAPT and early-onset autosomal dominant Alzheimer disease.