The presence of Tau protein in blood as a potential prognostic factor in stroke patients

Tau protein is found in the blood of 40 - 50% of patients in the acute phase of a stroke, as a result of the degradation of neurons and damage to the blood-brain barrier. The aim of the study was to assess the incidence of tau protein in the blood of stroke patients, as well as to evaluate the potential impact of tau protein presence in the blood of patients on their neurological state during the first 24 hours, and their functional condition three months after the stroke. Eighty-seven patients aged 39 - 99 (42 females and 45 males) diagnosed with stroke were enrolled in the prospective study (August 2014 - April 2015). The following parameters were analyzed in enrolled participants: the age at which first ischemic stroke occurred, neurological state during the first 24 hours (National Institutes of Health Stroke Scale - NIHSS), blood tau protein and brain derived neurotrophic factor (BDNF) concentrations on day 2 of stroke, the functional condition on day 90 after stroke onset (mRankin). A multifactorial analysis was carried out to establish independent factors for the presence of serum tau protein and to identify independent factors for poor prognosis. Eighty-seven patients of the mean age of 71.7 ± 11.8 years (median 74; min. 39 max. 99 years) took part in the study. The tau protein was found in the serum of 42 (48.27%) patients in the concentrations between 29.56 and 19 023.50 ng/ml. The female sex was the only independent factor for the presence of tau protein in blood (RR 4.49 (1.68 - 11.97), P = 0.003). The mean BDNF concentration in the evaluated group was: 9.96 ± 5.21; median 10.39. Three independent factors for poor functional condition of patients on day 90 after the stroke were identified: the presence of tau protein in blood (RR 3.90 (1.45 - 10.49), P = 0.007), BDNF concentration below the mean value for the study (RR 14.49 (4.60 - 45.45); P = 0.000) and NIHSS score > 4 during the first 24 hours of stroke (RR 1.14; 95% CI: 1.00 - 1.31; P = 0.027). The presence of the tau protein, low BDNF concentrations, and moderate/serious neurological state during the first 24 hours of stroke can be considered as negative prognosis for the patient's functional condition. The coincidence of high BDNF concentrations and absence of tau in blood during the acute phase of an ischemic stroke is a predictor of patient's good state in 3 months after stroke.