["The differentiation of Alzheimer's disease (AD) from vascular dementia (VaD) is hampered by clinical diagnostic criteria with disappointing sensitivity and specificity. The objective of this study was to investigate whether cerebrospinal fluid (CSF) levels of total tau protein (t-tau), amyloid beta42 protein (Abeta42), and tau phosphorylated at threonine 181 (p-tau181) are useful biomarkers to distinguish AD patients from VaD patients.", 'We measured CSF levels of p-tau181, Abeta42, and t-tau in 86 patients with a clinical diagnosis of AD or VaD and in 30 control participants.', 'Optimal differentiation between AD and VaD was achieved by using the ratio of the CSF levels of Abeta42 and p-tau181 (Q Abeta42/p-tau) with sensitivity, specificity, positive and negative predictive values all > or = 85%.'] Does cerebrospinal fluid amyloid beta42/phosphorylated tau ratio discriminate between Alzheimer 's disease and vascular dementia?