In order to be included in the reference database all subjects had to be cognitively normal with a Mini-Mental State Exam (MMSE) ≥ 25, be APOE ε4 negative on both alleles, be negative on QR-PiB, and have CSF levels of Aβ42, phosphorylated tau (p-tau), and total-tau (t-tau) in the non-AD range as defined by Miners et al. and described in the Materials and Methods section (Miners et al., 2019). Here, APOE is linked to Alzheimer disease.