Platelet count and platelet factor 3 (PF-3) availability in sickle cell disease.

In view of the effect of red blood cell membrane on platelet factor 3 release in sickle cell disease, platelet count and platelet factor 3 (PF-3) availability were measured in 30 sickle cell patients in a stable state and 15 with thrombocytosis, and these were compared with 60 non-sickle cell individuals as controls. There were no significant differences in platelet counts, but there was a slightly higher PF-3 availability in sickle cell patients not in crisis than in the controls (P < 0.025). Sickle cell patients with thrombocytosis made PF-3 available more readily than did the control individuals and sickle cell patients not in crisis (P < 0.001). We conclude that sickle cell patients are capable of making platelet factor 3 readily available for coagulation activation, and this may play a decisive role in vaso-occlusive crisis.