Assessment of VWF-GPIIb/IIIa binding under flow conditions. (A-B) CPA of platelet aggregation under flow conditions. (C-H) CPA of whole blood from volunteers carrying either the Phe2561 (n = 18) or the Tyr2561 allele (n = 13). (I-K) Phe2561 whole blood supplemented with 50 µg/mL of either recombinant Phe2561 (red bars) or Tyr2561 (blue bars). Aggregate size (C-E,I-K) and surface coverage (F-H) were determined at 1000 s⁻¹, 1800 s⁻¹, and 3000 s⁻¹ at the indicated points, aggregates were stained using May-Grünwald solution. Seven pictures per test were recorded employing a built-in microscope and camera and analyzed using the IMPACT-R image analyzer software. Each test was performed in duplicate at all points. Mean values ± SEM are shown. Asterisks indicate a significant difference between controls and Tyr2561 at each point (unpaired t-test, *P < .05; **P < .005; ***P < .0001).