CTRL and Alzheimer disease: Subjects with lower, pathological levels of Aβ-42 and Aβ42/40 ratio below the established cut-off values ((Aβ 42 < 192 pg/mL) [13,18] and Aβ42/40 ratio < 0.063 [25]), were named as positive (Aβ+, AD+, MCI+ and CTRL+), and those with higher levels (above established cut-off values) of the mentioned biomarkers as negative, Aβ- [13,18].