GPVI deficiency leads to abolished PS exposure under flow in the absence of coagulation. Whole blood from control, GP6^hom, and GP6^het subjects was recalcified in presence of PPACK and perfused over collagen (A) and noncollagen (B) (laminin, VWF, and rhodocytin) surfaces. Surface area coverage (SAC), PS exposure, and contraction score are presented as mean ± SD; control = 4, GP6^het = 4, and GP6^hom = 6. ****P < .0001, **P < .01, *P < .05. Representative bright-field and Alexa Fluor 647-Annexin A5 images are shown. Images were taken at the end point (8 min) after labeling was performed. (C) Whole blood from GP6^hom patients treated with the monoclonal antibody 6F1 (10 μg/mL) was recalcified and perfused over collagen (i) and noncollagen (ii) surfaces. Quantification of surface area coverage is presented as mean ± SD. GP6^hom= 2. Representative bright-field images are shown. Scale bars, 50 μm.