Thrombus generation on a collagen-coated surface by blood from patients with various congenital platelet aggregation disorders perfused under (A) low or (B) high shear rate. BSS, Bernard-Soulier syndrome; GTA, Glanzmann’s thrombasthenia; vWD, von Willebrand disease; Af, congenital afibrinogenemia. Images were taken at 1 minute and 7 minutes after the beginning of perfusion of blood from one patient with each disease (numbered as “−1”; see Table 1); control images are identical to those in Fig 1. (A) Note the nearly unchanged image of thrombus formation in GTA blood at 7 minutes of perfusion; all other images at both 1 minute and 7 minutes of perfusion are comparable with the control. (B) Images correspond to blood of patients in (A). Note the absence of platelet-surface interaction in BSS and type 3 vWD even at 7 minutes of perfusion. Note also that the extent of platelet-surface interaction in GTA blood is comparable with that of the normal control at 1 minute of perfusion, while thrombus growth is absent in the GTA patient even at 7 minutes of perfusion.