CSF-concentrations of tau-protein, phospho-tau-protein (181) and amyloid-beta (1–42) in patients with stable and non-stable MCI

Background: Cerebrospinal fluid (CSF) tau-protein, phospho-tau-protein (181) and amyloid-beta (1–42) are established biomarkers for the diagnosis of Alzheimer's dementia (AD). Patients with mild cognitive impairment (MCI) are at risk of converting to AD. In our study we characterized patients with stable and unstable MCI by CSF-biomarkers and neuropsychological parameters (CERAD). Methods: CSF biomarker concentrations were determined by ELISA in 22 patients with stable and 22 matched patients with unstable MCI. CERAD, Trail making test and logical memory testing were performed during follow-up in all patients. Results: Patients with unstable MCI showed significantly increased (p=0.008) CSF levels of tau-protein (558.55 +/- 285.27 pg/ml) compared to patients with stable MCI (364.91 +/- 157.27 pg/ml), while phospho-tau protein (181) was not significantly increased (p=0.47) between stable MCI (55.36 +/- 18.75 pg/ml) and unstable MCI (60.50 +/- 27.14 pg/ml). Amyloid-beta (1–42) was significantly decreased (p=0.003) in converters (319.09 +/- 128.52 pg/ml) compared to non-converters (475.86 +/- 199.21 pg/ml). Conclusions: CSF tau-protein is significantly increased in patients with MCI converting to AD, while phospho-tau-protein (181) is not and amyloid-beta (1–42) is decreased. These CSF biomarkers help to characterize a population at risk of developing manifest AD and should be determined in patients with newly diagnosed MCI.