APP and Alzheimer disease: Blood biomarkers serve as quantitative measures of brain injury and could potentially predict cognitive impairment.3, 4 Biomarkers phosphorylated tau at threonine 181 (p-tau181), total tau (t-tau), amyloid-beta peptides 40 (Aβ40) and 42 (Aβ42) demonstrate Alzheimer disease related changes and often correlate with cognitive decline, these are hereafter summarized as “Alzheimer disease biomarkers”.5