In the PiB- group, the cut-off points of plasma biomarkers for differentiating between controls and subjects with AD are much higher (tau 37.54 pg/ml and Aβ42 21.92 pg/ml) than those of their PiB+ counterparts (tau 25.57 pg/ml and Aβ42 16.81 pg/ml) (Table 3). This evidence concerns the gene MAPT and Alzheimer disease.