RBCs from patients with PV adhere more efficiently to HUVECs than RBCs from healthy volunteers under flow conditions and are resistant to wash-off by increasing shear stress. (A) A typical microscopic image shows that PV RBCs adhere to a higher extent to HUVECs than healthy volunteer RBCs after inflow at 0.03 Pa and washout (1.00 Pa). (B) Number of RBCs remaining adherent to HUVECs in microslides after inflow at 0.03 Pa and washout at increasing shear stress. (C) Number of RBCs adherent to HUVECs after inflow at different wall shear stresses **P < .01; ***P < .001 for PV RBCs compared with normal RBCs. Bars denote SEM.