Objective: To evaluate three biomarkers of dementia in cerebrospinal fluid (CSF): Total tau (T-tau), phospho tau (P-tau) and 42 amino acid form of beta amyloid (Aβ-42) in our clinical practice. Setting: Department of Neurology, Faculty Hospital Motol, Prague. Material and Methods: Biomarkers of dementia were determined in CSF of neurological patients (N = 155) by immunosorbent assay (ELISA) developed by Innogenetics. Selected subgroups are present: Probable Alzheimer disease (AD; N = 14), minimal cognitive impairment (MCI; N = 8), patients with pathologically confirmed diagnosis (N = 10): Creutzfeldt- Jacob disease (CJD; N = 3), Alzheimer disease (AD; N = 2), Pick disease (N = 1), Progressive supranuclear palsy (PSO; N = 1), Multiple system atrophy (MSA; N = 1), Amyotropic lateral sclerosis + frontotemporal dementia (ALS + FTD; N = 1), Amyotropic lateral sclerosis (ALS; N = 1) and a Control group (N = 37). Results: Probable AD group: Abnormal values of T-tau were found in all patients (100%), decreased Aβ-42 was detected in 13 patients (92%) and abnormal P-tau in 12 patients (86%). MCI patients Increased P-tau in 2 cases served as prognostic factor for AD. The group with pathologically confirmed diagnosis: CJD patients very high values of T-tau, normal P-tau in 2 patients and slighly increased in one, Aβ-42 was decreased in 1 case. AD patients: High T-tau, increased P-tau and decreased Aβ-42. Pick disease: High T-tau, P-tau was normal, A-42 decreased. PSP: All 3 biomarkers were normal. MSA: All 3 biomarkers were normal. ALS + FTD: Increased T-tau, P-tau and Aβ-42 were normal. ALS: Slightly increased T-tau, P-tau and Aβ-42 were normal. Control group: Normal T-tau and P-tau were found in all patients (100%). In 12 patients (32%) Aβ-42 was decreased. Conclusion: P-tau is more specific for diagnosis of AD than T-tau and Aβ-42, but it cannot fully replace the other CSF biomarkers especially in CJD or in patients with frontal cognitive impairment. This study confirms a good correlation of CSF biomarkers findings with autopsy based definitive diagnosis AD.

        Key words: CSF, total tau protein, phospho tau protein, beta amyloid, dementia.