PIGHP1 and Alzheimer disease: PIGHP1 was significantly upregulated in AD cases in the combined brain and blood samples in the ε2/ε3 group (Z = 4.67, P = 3.1×10−6, Padj = 0.05), a pattern predominated by the evidence in the brain but also apparent in the blood (Table 3, Supplementary Figs. 2, 3a).