title: Functional platelet defects in children with severe chronic ITP as tested with 2 novel assays applicable for low platelet counts.
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.
authors.affiliation: Department of Clinical Chemistry and Hematology, University Medical Center Utrecht, Utrecht, The Netherlands;
authors.forename: Esther R
authors.initials: ER
authors.lastname: van Bladel
authors.forename: Annemieke G
authors.initials: AG
authors.lastname: Laarhoven
authors.forename: Laila B
authors.initials: LB
authors.lastname: van der Heijden
authors.forename: Katja M
authors.initials: KM
authors.lastname: Heitink-Pollé
authors.forename: Leendert
authors.initials: L
authors.lastname: Porcelijn
authors.forename: C Ellen
authors.initials: CE
authors.lastname: van der Schoot
authors.forename: Masja
authors.initials: M
authors.lastname: de Haas
authors.forename: Mark
authors.initials: M
authors.lastname: Roest
authors.forename: Gestur
authors.initials: G
authors.lastname: Vidarsson
authors.forename: Philip G
authors.initials: PG
authors.lastname: de Groot
authors.forename: Marrie C A
authors.initials: MC
authors.lastname: Bruin
mesh_terms: D000293:Adolescent; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D015539:Platelet Activation / Q000187:drug effects; D010974:Platelet Aggregation / Q000187:drug effects; D010976:Platelet Count; D010979:Platelet Function Tests / Q000379:methods*; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000175:diagnosis* / Q000378:metabolism*; D015203:Reproducibility of Results; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D013755:Tetradecanoylphorbol Acetate