title: Differences in platelet function in patients with acute myeloid leukemia and myelodysplasia compared to equally thrombocytopenic patients with immune thrombocytopenia.
abstract: BACKGROUND
  Severe thrombocytopenia is a major risk factor for hemorrhage, but platelet function and bleeding risk at low platelet counts are poorly understood, because of the limitations of platelet function testing at very low platelet counts.
  
  
  OBJECTIVE
  To examine and compare platelet function in severely thrombocytopenic patients with acute myeloid leukemia (AML) or myelodysplasia (MDS) with that in patients with immune thrombocytopenia (ITP).
  
  
  METHODS
  Whole blood flow cytometric measurement of platelet activation and platelet reactivity to agonists was correlated with the immature platelet fraction (IPF) and bleeding symptoms.
  
  
  RESULTS
  Patients with AML/MDS had smaller platelets, lower IPF and substantially lower platelet surface expression of activated glycoprotein (GP)IIb-IIIa and GPIb, both with and without addition of ex vivo ADP or thrombin receptor-activating peptide, than patients with ITP. In both ITP and AML/MDS patients, increased platelet surface GPIb on circulating platelets and expression of activated GPIIb-IIIa and GPIb on ex vivo activated platelets correlated with a higher IPF. Whereas platelet reactivity was higher for AML/MDS patients with bleeding than for those with no bleeding, platelet reactivity was lower for ITP patients with bleeding than for those with no bleeding.
  
  
  CONCLUSIONS
  AML/MDS patients have lower in vivo platelet activation and ex vivo platelet reactivity than patients with ITP. The proportion of newly produced platelets correlates with the expression of platelet surface markers of activation. These differences might contribute to differences in bleeding tendency between AML/MDS and ITP patients. This study is the first to define differences in platelet function between AML/MDS patients and ITP patients with equivalent degrees of thrombocytopenia.
authors.affiliation: Platelet Disorders Center, Division of Pediatric Hematology-Oncology, Weill-Cornell Medical College, New York, NY, USA.
authors.forename: B
authors.initials: B
authors.lastname: Psaila
authors.forename: J B
authors.initials: JB
authors.lastname: Bussel
authors.forename: A L
authors.initials: AL
authors.lastname: Frelinger
authors.forename: B
authors.initials: B
authors.lastname: Babula
authors.forename: M D
authors.initials: MD
authors.lastname: Linden
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: M R
authors.initials: MR
authors.lastname: Barnard
authors.forename: C
authors.initials: C
authors.lastname: Tate
authors.forename: E J
authors.initials: EJ
authors.lastname: Feldman
authors.forename: A D
authors.initials: AD
authors.lastname: Michelson
mesh_terms: D000368:Aged; D001792:Blood Platelets / Q000473:pathology / Q000502:physiology*; D048430:Cell Shape; D005260:Female; D005434:Flow Cytometry; D006470:Hemorrhage; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009190:Myelodysplastic Syndromes / Q000097:blood*; D015539:Platelet Activation; D010980:Platelet Membrane Glycoproteins / Q000032:analysis; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000097:blood*
chemical_list: D010980:Platelet Membrane Glycoproteins