CSFtau

CSFtau refers to tau protein measurements in cerebrospinal fluid. The most commonly reported forms are total tau (t-tau), indicating overall neuronal damage, and phosphorylated tau (p-tau), reflecting tau phosphorylation associated with neurofibrillary pathology. In some contexts, "CSF tau" is used to denote t-tau specifically.

In clinical practice, CSF tau is used as part of a biomarker profile to assess suspected neurodegenerative disease. In Alzheimer's disease, CSF t-tau and p-tau are often elevated, while CSF Aβ42 is reduced, producing a pattern that supports amyloid and tau–related pathology. Elevated t-tau is a general sign of neuronal injury and is not specific to Alzheimer's disease, whereas elevations of p-tau, particularly certain phosphorylated forms, tend to be more closely associated with Alzheimer's–type pathology but are not perfectly specific. The biomarkers are most informative when interpreted together with Aβ42 and the clinical presentation.

Measurement and interpretation rely on lumbar puncture to collect CSF, followed by immunoassay analysis. Pre-analytical factors such as sample handling, storage, and the analytical method can influence results; therefore, reference ranges and cutoffs vary by assay and laboratory. Results should be interpreted in the clinical context, and in many settings, CSF tau is used alongside other biomarkers to support diagnosis and differential diagnosis among dementias.

Limitations include limited disease specificity and overlap with other conditions causing neuronal injury. CSF tau is a valuable, but not definitive, tool in the assessment of cognitive impairment and neurodegenerative disease.