Estimation of Tau and Phosphorylated Tau(181) in Serum of Alzheimer’s Disease and Mild Cognitive Impairment Patients

The elevated level of cerebrospinal fluid (CSF) Tau and phosphorylated Tau(181) (p-Tau(181)) proteins are well established hallmarks of Alzheimer’s disease (AD). Elevated level of p-Tau(181) can differentiate AD from other neurodegenerative disease. However, the expression level of these proteins in serum of AD patient is not well set up. This study sought to evaluate the level of Tau and p-Tau(181) in serum of AD, and mild cognitive impairment (MCI) patients for an alternative approach to establish protein-based markers by convenient way. Blood samples were collected from 39 AD patients, 37 MCI patients and 37 elderly individuals as controls. The levels of Tau and p-Tau(181) in the serum of the different groups were measured by label free real time Surface Plasmon Resonance technology by using specific antibodies, and were further confirmed by the conventional western blot method. An appropriate statistical analysis, including Receiver Operating Characteristic (ROC), was performed. The concentrations of serum Tau and p-Tau(181) were significantly higher (p<0.00001) in AD (Tau; 47.49±9.00ng/μL, p-Tau(181); 0.161±0.04 ng/μL) compared to MCI (Tau; 39.26±7.78 ng/μL, p-Tau(181); 0.135±0.02 ng/μL) and were further higher compared to elderly controls (Tau; 34.92±6.58 ng/μL, p-Tau(181); 0.122±0.01 ng/ μL). A significant (p<0.0001) downhill correlation was found between Tau as well as p-Tau(181) levels with HMSE and MoCA score. This study for the first time reports the concentration of Tau and p-Tau(181) in serum of AD and MCI patients. The cutoff values of Tau and p-Tau(181) of AD and MCI patients with sensitivity and specificity reveal that serum level of these proteins can be used as a predictive marker for AD and MCI.