Effect of in vivo DDAVP on platelet aggregation in PRP. Whole blood was drawn before and 4 hours after start of the DDAVP infusion in 10 patients with congenital platelet function defects. (A) ADP-induced platelet aggregation at 3 minutes, (B) lag phase of collagen-induced platelet aggregation, (C) collagen-induced platelet aggregation at 3 minutes, (D) lag phase of arachidonate-induced platelet aggregation, (E) arachidonate-induced platelet aggregation at 3 minutes, and (F) ristocetin-induced platelet agglutination at 3 minutes. See “Material and methods” for details on agonist concentrations. Changes were not statistically significant (see Table 1 for P values). In panels A-C, the symbols depict paired values for individual patients, before and after DDAVP.