CD81 and Alzheimer disease: NDEV total tau levels increased with disease severity (Fig. 1b), were significantly elevated in mild-to-moderate AD (p < 0.01; CD81-adjusted levels: 97.16 pg/ml) and in advanced AD (p < 0.001; CD81-adjusted levels: 140.85 pg/ml) compared with controls and were higher in advanced AD cases than in mild-to-moderate AD patients (p < 0.05).