Platelet surface markers of activation in responders and nonresponders to eltrombopag treatment with no added agonist and in response to low and high dose ADP and TRAP stimulation. (A-C) Responders and (D-F) nonresponders. (A,D) Activated GPIIb/IIIa (PAC-1), (B,E) P-selectin, and (C,F) GPIb. C indicates healthy controls; D0, ITP patients pretreatment with eltrombopag; D7 and D28, 7 and 28 days after initiation of eltrombopag treatment in ITP patients. Data are mean ± SEM (*P < .05; **P < .02; ***P < .001).