The single AD candidate gene represented in the plasma dataset, GPC2, was shown to be downregulated in AD cases when compared to control subjects; neither tau protein (encoded by MAPT gene) nor the other cognitive and structural candidates represented in this dataset (ARTN, CA13, CAMK2B, CTSA, EPHA3, MAPT, MST1R, and ULBP) showed differences between AD cases and controls in plasma. The gene discussed is MAPT; the disease is Alzheimer disease.