Functional platelet defects in children with severe chronic ITP as tested with 2 novel assays applicable for low platelet counts

Blood. 2014 Mar 6;123(10):1556-63. doi: 10.1182/blood-2013-08-519686. Epub 2014 Jan 2.

Abstract

Immune thrombocytopenia (ITP) is an autoimmune disease with a complex heterogeneous pathogenesis and a bleeding phenotype that is not necessarily correlated to platelet count. In this study, the platelet function was assessed in a well-defined cohort of 33 pediatric chronic ITP patients. Because regular platelet function test cannot be performed in patients with low platelet counts, 2 new assays were developed to determine platelet function: first, the microaggregation test, measuring in platelets isolated from 10 mL of whole blood the platelet potential to form microaggregates in response to an agonist; second, the platelet reactivity assay, measuring platelet reactivity to adenosine diphosphate (ADP), convulxin (CVX), and thrombin receptor activator peptide in only 150 μL of unprocessed whole blood. Patients with a severe bleeding phenotype demonstrated a decreased aggregation potential upon phorbol myristate acetate stimulation, decreased platelet degranulation following ADP stimulation, and a higher concentration of ADP and CVX needed to activate the glycoprotein IIbIIIa complex compared with patients with a mild bleeding phenotype. In conclusion, here we have established 2 functional tests that allow for evaluation of platelet function in patients with extremely low platelet counts (<10(9)). These tests show that platelet function is related to bleeding phenotype in chronic ITP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Blood Platelets / drug effects
  • Blood Platelets / metabolism*
  • Child
  • Child, Preschool
  • Female
  • Humans
  • Male
  • Platelet Activation / drug effects
  • Platelet Aggregation / drug effects
  • Platelet Count*
  • Platelet Function Tests / methods*
  • Purpura, Thrombocytopenic, Idiopathic / diagnosis*
  • Purpura, Thrombocytopenic, Idiopathic / metabolism*
  • Reproducibility of Results
  • Tetradecanoylphorbol Acetate / pharmacology

Substances

  • Tetradecanoylphorbol Acetate