Blood level of β-amyloid, Tau, and p-Tau in mild cognitive impairment and Alzheimer disease: A follow up study

Background and objectives Deposition of β-amyloid and phosphorylated-tau proteins are major neuropathological abnormality in brain of patients with Alzheimer disease. This study aimed to study the role of various serum protein biomarkers to aid in the diagnosis and progression of Alzheimer disease. Methods Blood samples were collected from 96 patients with Alzheimer disease, 75 patients with mild cognitive impairment, and 70 geriatric controls at baseline. The number of patients (Alzheimer disease and mild cognitive impairment) who progressed after 1 year was 12, while the number of non-progressors was 24. Serum levels of β-amyloid1-42 (Aβ1-42), Tau, and phosphorylated-Tau181 (pTau) were quantified using surface plasmon resonance and further validated by Western blot. Results Comparison of proteins between the three groups revealed significantly lower Aβ1-42, higher Tau and pTau protein expression in serum of patients with Alzheimer disease as compared to patients with mild cognitive impairment and controls. In patients who progressed after one year, the baseline concentration of Aβ1-42 protein was significantly higher than their follow-up levels. Tau and pTau levels also increased significantly over the years. In non-progressors, no significant difference was observed in Aβ1-42, Tau, and pTau concentration between the baseline and follow up. Interpretation and conclusions Aβ1-42, Tau, and pTau proteins can serve as potential blood-based biomarkers for the diagnosis and monitoring the progression of Alzheimer disease.