MAPT and Alzheimer disease: Decreasing plasma Aβ of 42 amino acids/ Aβ of 40 amino acids (Aβ1–42/Aβ1–40) ratio (8–10) and increasing plasma total tau and p-tau (phosphorylated tau) levels correlate with abnormal Aβ and tau protein deposition in PET scans of MCI and AD patients (11) and differentiate diagnostic groups, including cognitively unimpaired (CU) vs early AD (12).