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

Blood (Impact Factor: 9.78). 01/2014; 123(10). DOI: 10.1182/blood-2013-08-519686
Source: PubMed

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. Since regular platelet function test cannot be performed in patients with low platelet counts, two new assays were developed to determine platelet function. First, the micro aggregation test measuring in platelets isolated from 10 ml whole blood, the platelet potential to form micro-aggregates in response to an agonist. Second, the platelet reactivity assay, measuring platelet reactivity to ADP, convulxin (CVX) and thrombin receptor activator peptide (TRAP) in only 150 µL unprocessed whole blood. Patients with a severe bleeding phenotype, demonstrated a decreased aggregation potential upon phorbol myristate acetate (PMA) stimulation, decreased platelet degranulation following ADP stimulation and a higher concentration of ADP and convulxin needed to activate the glycoprotein IIbIIIa complex compared to patients with a mild bleeding phenotype. In conclusion, here we have established two functional tests that allows 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.