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. 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.
[Show abstract] [Hide abstract]
ABSTRACT: Platelets are key cells in atherosclerosis and acute cardiovascular events. Platelet hyperreactivity and increased platelet-monocyte aggregation (PMA) are found in HIV-infected patients and may contribute to the excess cardiovascular risk. The integrase inhibitor raltegravir (RAL) has been associated with better residual viral suppression and reduction in inflammatory and coagulation biomarkers. The aim of our study was to investigate whether RAL-treated patients have reduced platelet reactivity and PMA.AIDS (London, England) 09/2014; 28(14):2091-2096. DOI:10.1097/QAD.0000000000000415 · 6.56 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Objective: Platelet reactivity, platelet binding to monocytes and monocyte infiltration play a detrimental role in atherosclerotic plaque progression. We investigated whether platelet reactivity was associated with levels of circulating platelet-monocyte complexes (PMCs) and macrophages in human atherosclerotic carotid plaques. Methods: Platelet reactivity was determined by measuring platelet P-selectin expression after platelet stimulation with increasing concentrations of adenosine diphosphate (ADP), in two independent cohorts: the Circulating Cells cohort (n = 244) and the Athero-Express cohort (n = 91). Levels of PMCs were assessed by flow cytometry in blood samples of patients who were scheduled for percutaneous coronary intervention (Circulating Cells cohort). Monocyte infiltration was semi-quantitatively determined by histological examination of atherosclerotic carotid plaques collected during carotid endarterectomy (Athero-Express cohort). Results: We found increased platelet reactivity in patients with high PMCs as compared to patients with low PMCs (median (interquartile range): 4153 (1585-11267) area under the curve (AUC) vs. 9633 (3580-21565) AUC, P<0.001). Also, we observed increased platelet reactivity in patients with high macrophage levels in atherosclerotic plaques as compared to patients with low macrophage levels in atherosclerotic plaques (mean +/- SD; 8969 +/- 3485 AUC vs. 7020 +/- 3442 AUC, P = 0.02). All associations remained significant after adjustment for age, sex and use of drugs against platelet activation. Conclusion: Platelet reactivity towards ADP is associated with levels of PMCs and macrophages in human atherosclerotic carotid plaques.PLoS ONE 08/2014; 9(8):e105019. DOI:10.1371/journal.pone.0105019 · 3.53 Impact Factor