Platelet spreading on collagen, VWF, and glass. (A) Human platelets (2 × 10⁷/mL) were spread on coated and uncoated (not blocked) coverslips as described in “Methods.” The images are representative of 3 control and 3 GP6^hom patients. (B) The graphs illustrate quantification of surface area and the percentage of fully, partially spread, or nonspread platelets (control = 3, GP6^het = 2, GP6^hom = 3). Measurements are the mean of 48 882 platelets in a replicate (7 fields of view per replicate), and the figures are representative of part of a field of view. Significance was measured using 2-way ANOVA. **P < .01, ***P < .001; ****P < .0001. The surface area in the field of view is 213 × 213 μm. Scale bar, 50 μm.