Cerebrospinal fluid biomarkers (the 42 amino acid form of β-amyloid (Aβ), total tau, and phosphorylated tau) have been evaluated in scientific studies. Tau proteins are considered "state" markers, whereas Aβ(1-42) proteins can be used as "stage" markers. These CSF markers have high sensitivity to differentiate early AD from normal aging, depression, alcohol dementia and Parkinson's disease. When these biomarkers are used in combination with a medical history, clinical examination, laboratory tests and brain imaging, the diagnostic accuracy is improved.