Protein A immunoadsorption in chronic refractory ITP reverses increased platelet activation but fails to achieve sustained clinical benefit

Platelet features allow to differentiate immune thrombocytopenia from inherited thrombocytopenia

Immune thrombocytopenia (ITP) is an acquired bleeding disorder, for which no specific diagnostic test exists. Inherited thrombocytopenia (IT) can mimic ITP and lead to unappropriated management with significant morbidity. Here, in small cohorts of these two disorders, we explored whether platelet sialylation and platelet activation could allow to discriminate the two conditions. We also aimed to confirm the value of immature platelet counts in this discrimination. Platelet sialylation and the expression level of P-selectin were assessed by multiparameter flow cytometry. Immature platelets were estimated on a Sysmex XN 9000 analyzer. No significant difference in platelet sialylation was observed between ITP and IT. Contrarily, platelet activation was significantly higher in ITP patients (p = 0.008). The immature platelet fraction, as previously demonstrated, was significantly lower in the ITP group compared to the IT group (p = 0.014). That statistical significance was achieved in this small pilot study suggests that the two easily available assays of immature platelet count and P-selectin expression could help physicians to reach the proper diagnosis in complex cases of thrombocytopenia.

Platelet function and bleeding at different phases of childhood immune thrombocytopenia

Immune thrombocytopenia (ITP) is believed to be associated with platelet function defects. However, their mechanisms are poorly understood, in particular with regard to differences between ITP phases, patient age, and therapy. We investigated platelet function and bleeding in children with either persistent or chronic ITP, with or without romiplostim therapy. The study included 151 children with ITP, of whom 56 had disease duration less than 12 months (grouped together as acute/persistent) and 95 were chronic. Samples of 57 healthy children were used as controls, while 5 patients with leukemia, 5 with aplastic anemia, 4 with MYH9-associated thrombocytopenia, and 7 with Wiskott-Aldrich syndrome were used as non-ITP thrombocytopenia controls. Whole blood flow cytometry revealed that platelets in both acute/persistent and chronic ITP were increased in size compared with healthy donors. They were also pre-activated as assessed by PAC1, CD62p, cytosolic calcium, and procoagulant platelet levels. This pattern was not observed in other childhood thrombocytopenias. Pre-activation by CD62p was higher in the bleeding group in the chronic ITP cohort only. Romiplostim treatment decreased size and pre-activation of the patient platelets, but not calcium. Our data suggest that increased size, pre-activation, and cytosolic calcium are common for all ITP platelets, but their association with bleeding could depend on the disease phase.

Hemostatic changes by thrombopoietin-receptor agonists in immune thrombocytopenia patients

Thrombopoietin receptor agonist (TPO-RA) treatment increases the thrombosis rate in immune thrombocytopenia (ITP). We hypothesize that TPO-RAs influence platelet function, global and secondary hemostasis and/or fibrinolysis. A systematic review was performed. If possible, data were compared between responders (relevant increase in platelet count), and non-responders. Twelve observational studies with 305 patients were included (responders (127/150 (85%))). There were indications that TPO-RA treatment enhanced platelet function, with respect to platelet-monocyte aggregates, soluble P-selectin, GPVI expression, and adhesion under flow. Studies addressing global and secondary hemostasis and fibrinolysis were scarce. Overall, no changes were found during TPO-RA treatment, apart from an accelerated clot formation and conflicting data on levels of plasminogen activator inhibitor (PAI)-1. The parameters that increased have previously been associated with thrombosis in other patient groups, and might contribute to the increased rate of thrombosis observed in TPO-RA-treated ITP patients.

Heterogeneity of Integrin αIIbβ3 Function in Pediatric Immune Thrombocytopenia Revealed by Continuous Flow Cytometry Analysis

Immune thrombocytopenia (ITP) is an autoimmune condition primarily induced by the loss of immune tolerance to the platelet glycoproteins. Here we develop a novel flow cytometry approach to analyze integrin α_IIbβ₃ functioning in ITP in comparison with Glanzmann thrombasthenia (GT) (negative control) and healthy pediatric donors (positive control). Continuous flow cytometry of Fura-Red-loaded platelets from whole hirudinated blood was used for the characterization of platelet responses to conventional activators. Calcium levels and fibrinogen binding were normalized to ionomycin-induced responses. Ex vivo thrombus formation on collagen was observed in parallel-plate flow chambers. Platelets from all ITP patients had significantly higher cytosolic calcium concentration in the quiescent state compared to healthy donors (15 ± 5 nM vs. 8 ± 5 nM), but calcium increases in response to all activators were normal. Clustering analysis revealed two subpopulations of ITP patients: the subgroup with high fibrinogen binding (HFB), and the subgroup with low fibrinogen binding (LFB) (8% ± 5% for LFB vs. 16% ± 3% for healthy donors in response to ADP). GT platelets had calcium mobilization (81 ± 23 nM), fibrinogen binding (5.1% ± 0.3%) and thrombus growth comparable to the LFB subgroup. Computational modeling suggested phospholipase C-dependent platelet pre-activation for the HFB subgroup and lower levels of functional integrin molecules for the LFB group.

Guidelines on the Use of Therapeutic Apheresis in Clinical Practice - Evidence-Based Approach from the Writing Committee of the American Society for Apheresis: The Eighth Special Issue

The American Society for Apheresis (ASFA) Journal of Clinical Apheresis (JCA) Special Issue Writing Committee is charged with reviewing, updating and categorizing indications for the evidence-based use of therapeutic apheresis (TA) in human disease. Since the 2007 JCA Special Issue (Fourth Edition), the committee has incorporated systematic review and evidence-based approaches in the grading and categorization of apheresis indications. This Eighth Edition of the JCA Special Issue continues to maintain this methodology and rigor in order to make recommendations on the use of apheresis in a wide variety of diseases/conditions. The JCA Eighth Edition, like its predecessor, continues to apply the category and grading system definitions in fact sheets. The general layout and concept of a fact sheet that was introduced in the Fourth Edition, has largely been maintained in this edition. Each fact sheet succinctly summarizes the evidence for the use of TA in a specific disease entity or medical condition. The Eighth Edition comprises 84 fact sheets for relevant diseases and medical conditions, with 157 graded and categorized indications and/or TA modalities. The Eighth Edition of the JCA Special Issue seeks to continue to serve as a key resource that guides the utilization of TA in the treatment of human disease.

Guidelines on the Use of Therapeutic Apheresis in Clinical Practice-Evidence-Based Approach from the Writing Committee of the American Society for Apheresis: The Seventh Special Issue

The American Society for Apheresis (ASFA) Journal of Clinical Apheresis (JCA) Special Issue Writing Committee is charged with reviewing, updating, and categorizing indications for the evidence-based use of therapeutic apheresis in human disease. Since the 2007 JCA Special Issue (Fourth Edition), the Committee has incorporated systematic review and evidence-based approaches in the grading and categorization of apheresis indications. This Seventh Edition of the JCA Special Issue continues to maintain this methodology and rigor to make recommendations on the use of apheresis in a wide variety of diseases/conditions. The JCA Seventh Edition, like its predecessor, has consistently applied the category and grading system definitions in the fact sheets. The general layout and concept of a fact sheet that was used since the fourth edition has largely been maintained in this edition. Each fact sheet succinctly summarizes the evidence for the use of therapeutic apheresis in a specific disease entity. The Seventh Edition discusses 87 fact sheets (14 new fact sheets since the Sixth Edition) for therapeutic apheresis diseases and medical conditions, with 179 indications, which are separately graded and categorized within the listed fact sheets. Several diseases that are Category IV which have been described in detail in previous editions and do not have significant new evidence since the last publication are summarized in a separate table. The Seventh Edition of the JCA Special Issue serves as a key resource that guides the utilization of therapeutic apheresis in the treatment of human disease. J. Clin. Apheresis 31:149-162, 2016. © 2016 Wiley Periodicals, Inc.

Platelet function tests, independent of platelet count, are associated with bleeding severity in ITP

Immune thrombocytopenia (ITP) patients with similarly low platelet counts differ in their tendency to bleed. To determine if differences in platelet function in ITP patients account for this variation in bleeding tendency, we conducted a single-center, cross-sectional study of pediatric patients with ITP. Bleeding severity (assessed by standardized bleeding score) and platelet function (assessed by whole blood flow cytometry) with and without agonist stimulation was evaluated in 57 ITP patients (median age, 9.9 years). After adjustment for platelet count, higher levels of thrombin receptor activating peptide (TRAP)-stimulated percent P-selectin- and activated glycoprotein (GP)IIb-IIIa-positive platelets were significantly associated with a lower bleeding score, whereas higher levels of immature platelet fraction (IPF), TRAP-stimulated platelet surface CD42b, unstimulated platelet surface P-selectin, and platelet forward light scatter (FSC) were associated with a higher bleeding score. Thus, platelet function tests related to platelet age (IPF, FSC) and activation through the protease activated receptor 1 (PAR1) thrombin receptor (TRAP-stimulated P-selectin, activated GPIIb-IIIa, and CD42b), independent of platelet count, are associated with concurrent bleeding severity in ITP. These tests may be useful markers of future bleeding risk in ITP.

Effect of steroids on the activation status of platelets in patients with Immune thrombocytopenia (ITP)

The activation status of platelets in Immune Thrombocytopenia (ITP) patients--which is still somewhat controversial--is of potential interest, because activated platelets tend to aggregate (leading to excessive clotting or thromboembolic events) but cannot do so when platelet numbers are low, as in ITP. Although corticosteroids are the first line of therapy in ITP, the effect of steroids on activation of platelets has not been evaluated so far. We examined the status of platelet activation (with and without stimulation with ADP) in ITP patients, at the start of therapy (pre-steroid treatment, naive) and post-steroid treatment (classified on the basis of steroid responsiveness). We used flow cytometry to evaluate the levels of expression of P-selectin, and PAC-1 binding to platelets of 55 ITP patients and a similar number of healthy controls, treated with and without ADP. We found that platelets in ITP patients exist in an activated state. In patients who are responsive to steroids, the treatment reverses this situation. Also, the fold activation of platelets upon treatment with ADP is more in healthy controls than in ITP patients; treatment with steroids causes platelets in steroid-responsive patients to become more responsive to ADP-activation, similar to healthy controls. Thus steroids may cause changes in the ability of platelets to get activated with an agonist like ADP. Our results provide new insights into how, and why, steroid therapy helps in the treatment of ITP.

Agonist-inducible platelet activation in chronic idiopathic autoimmune thrombocytopenia

OBJECTIVE

There are only few studies on agonist-inducible platelet activation in chronic idiopathic autoimmune thrombocytopenia (cAITP).

MATERIALS AND METHODS

We compared agonist (TRAP-6, ADP, Arachidonic acid, Epinephrine, and Ristocetin) -inducible P-selectin expression and PAC-1 binding in 40 patients with cAITP (f/m ratio 23/17) with those in 20 healthy controls. Results were correlated with platelet counts, detectable platelet antibodies, and reticulated platelets.

RESULTS

The in vivo activation of platelets determined the in vitro inducible response to agonists. The stronger the in vivo activation the less the number of platelets responding to agonists, as illustrated by the inverse correlation of P-selectin expression ex vivo and the relative increase after the exogenous addition of agonists. The agonist-inducible platelet activation was not associated with the presence of detectable platelet antibodies to GPIb/IX or GPIIb/IIIa. Agonist-inducible platelet activation was also not correlated with counts of reticulated platelets.

CONCLUSION

Agonist-inducible activation of platelets in cAITP is affected mainly by their in vivo activation.

Management of immune thrombocytopenic purpura in adults

Primary immune thrombocytopenic purpura (ITP), also referred to as idiopathic thrombocytopenic purpura, is an organ-specific autoimmune disorder in which antibody-coated or immune complex-coated platelets are destroyed prematurely by the reticuloendothelial system, resulting in peripheral blood thrombocytopenia. The disease is heterogeneous with regard to its severity and clinical course and is unpredictable in its response to therapy. Although the basic underlying pathophysiology of ITP has been known for more than 50 years, current treatment guidelines are based on expert opinion rather than on evidence because of a lack of high-quality clinical trials and research. The only patients for whom treatment is clearly required are those with severe bleeding and/or extremely low platelet counts (< 10 x 10(9)/L). Treatment of patients with ITP refractory to corticosteroids and splenectomy requires careful evaluation of disease severity, patient characteristics related to risk of bleeding, and adverse effects associated with treatment. Clinical trials with numerous new agents are under way, which we hope will add more effective and targeted strategies to our therapeutic armamentarium. We describe a logical and structured approach to the clinical management of ITP in adults, based on a literature review and our personal experience.

Refractory idiopathic immune thrombocytopenic purpura in children: current and future treatment options

A minority of children with idiopathic or immune thrombocytopenic purpura (ITP) have the refractory chronic form with bleeding problems (stage III or IV). The aim of this article is to provide an update on the immunopathogenesis and management of children with bleeding and severe refractory ITP. The management of such patients, according to a staging guideline, is described. Recent clinical and laboratory observations document the disturbed immune responses that occur on various levels in chronic ITP. New therapeutic options are directed towards influencing these immunopathogenic mechanisms. Because ITP is not adequately defined and has heterogeneous manifestations, today's management recommendations are largely opinion-based rather than evidence-based. In severe refractory childhood ITP, consensus between the treating physician and the patient has to be achieved on an individual basis. The aim is to maintain the disease at stages I or II, with minimal intervention, and to prevent bleeding. If bleeding is not under control, medical treatment (as described in this article), or splenectomy, has to be considered.Although there is a paucity of data relating to children, potential new treatment options for refractory ITP include strategies aimed at influencing antigenemia, the T cell immune response (e.g. cyclosporine, CTLA-4-Ig) or the B-cell immune response (e.g. anti-CD20 monoclonal antibody, anti-CD52 monoclonal antibody, interferon). New prospective, cooperative ITP registries have been created to search for subgroups with different severities of ITP, which will be the selection criteria of future controlled studies in pediatric patients with refractory ITP.

Plasmapheresis in immune hematology: review of clinical outcome data with respect to evidence-based medicine and clinical experience

The objective of this paper is to assess the role of plasmapheresis in immune hematology by reviewing published clinical outcome data and narrative review articles. This information will be used to define evidence levels for appraisal of the efficacy and rank of plasmapheresis among other management options. This evidence-based strategy conforms to the concepts of the American Society of Hematology (ASH). as put forward in 1996 in the context of immune thrombocytopenia (ITP) treatment. The term 'experimental' is used to describe indications where the only scientific evidence of the efficacy of plasmapheresis consists of pathophysiological reasoning and empiric clinical findings. We reviewed the available literature on the use of plasmapheresis in autoimmune hemolytic anemia (AIHA), hemolytic disease of the newborn (HDN), autoimmune thrombocytopenic purpura (AITP), heparin-induced thrombocytopenia type II (HIT II), post-transfusion purpura (PTP), refractoriness to platelet transfusion (RPT), coagulation factor inhibitor (CFI) and catastrophic antiphospholipid syndrome (CAS). Plasmapheresis completes the spectrum of management options as it eliminates physically circulating free antibodies involved in the pathogenesis of these immune hematological syndromes. Because of the paucity of data, evidence levels had to be defined based on the findings of uncontrolled case series and the opinions of independent experts. In many cases, randomized clinical trials were not feasible because the syndromes are so rare. When defined as an 'experimental indication', plasmapheresis has a firm scientific basis, but larger scale clinical experience with the method is still lacking. In these cases, the detection and monitoring of symptomatic disease-related circulating free antibodies or immune complexes is a mandatory prerequisite for the use of plasmapheresis. The therapeutic benefit of plasmapheresis is substantiated by the level V of evidence of its efficacy in treatment of HDN, HIV-associated AITP, induction of tolerance in CFI and in CAS. The goal of future studies should be to establish a firmer base of scientific evidence for indications classified as experimental by setting up case series large enough for proper assessment of plasmapheresis alone or combination with other treatment measures. This goal can only be achieved through multiinstitutional cooperation.

Soluble P-selectin, interleukin 6, and thrombopoietin levels in children with acute and chronic idiopathic thrombocytopenic purpura and their relationship with mega-dose methylprednisolone therapy: a pilot study

We observed less severe symptoms in patients with chronic idiopathic thrombocytopenic purpura (ITP) than in patients with acute ITP with similar platelet counts. Thrombopoietin (TPO), soluble P-selectin, soluble P-selectin per platelet, and interleukin 6 (IL-6) were evaluated in children with ITP before treatment in 16 acute and 22 chronic cases and after treatment in 10 acute and chronic cases who received mega-dose methylprednisolone. The levels of IL-6, soluble P-selectin, soluble P-selectin per platelet, and platelet count were similar in acute and chronic ITP (P > 0.05) but TPO in acute ITP was higher than that of the patients with chronic ITP (P < 0.05). The posttreatment IL-6 and TPO declined (P < 0.05), but soluble P-selectin and platelet count increased (P < 0.05). Posttreatment soluble P-selectin per platelet levels were higher than the normal values (P < 0.05). These results suggest that IL-6, soluble P-selectin, and soluble P-selectin per platelet are not responsible for the milder symptoms in chronic than in acute ITP. Mega-dose methylprednisolone seems to keep the soluble P-selectin levels elevated.

Pathophysiology of platelet destruction in immune (idiopathic) thrombocytopenic purpura

The mechanism of platelet destruction in immune (idiopathic) thrombocytopenic purpura (ITP) is thought to involve production of autoantibody to platelet surface antigens. Once coated with antibody, circulating platelets undergo sequestration via interaction with Fc receptors of macrophages in the reticuloendothelial system. A number of questions remain about the mechanism of platelet destruction in this disease: 1) What is the nature of the stimulus to the immune system that generates antiplatelet antibodies? 2) What is the role of interactions between T-helper lymphocytes and antigen-presenting cells in ITP? 3) What role, if any, is played by the targeting of single or multiple platelet surface glycoproteins by the autoimmune response? 4) Is the site of platelet destruction, intravascular or extravascular, or the state of activation of platelets important in the destruction of platelets?

Management of adult immune thrombocytopenia

Immune thrombocytopenia (ITP) is a heterogeneous disease with regard to pathogenesis, severity, spontaneous course and response to treatment. Except in patients with severe bleeding tendency and very low platelet counts (< 10 x 10(9)/L), there are no clear rules on the indications for treatment. The standard initial therapy is corticosteroids, but the optimal dose and duration of therapy is unknown and in practice, some patients may be overtreated by aiming for complete remission (CR). In patients who have no sustained response after steroids, the most effective single therapy is splenectomy. Laparascopic splenectomy has a very low mortality and moderate morbidity. Preoperative prediction of success is difficult. About 50% of patients are in CR or partial remission after 5 years, but there are few data on the long-term outcome. Patients who fail steroids and splenectomy are difficult to treat. The choice may be palliative, with low doses of steroids or aggressive therapy with the intention of sustained remission. In selected patients, high-dose immunoglobulin or anti-D may be useful to temporarily raise the platelet count. Other drugs tried in ITP had either no or very limited clinically meaningful efficacy.

Immunoadsorption, current status and future developments

The association of abnormalities in the cellular and humoral immune system with various autoimmune diseases provides the rationale for apheresis technologies. While plasmapheresis or plasma exchange is limited by its non-selective removal of all plasma components, modern apheresis techniques aim to provide more specific elimination according to clinical needs and avoid plasma product replacement. However, the commercialisation has not met the expectations in the early 80's and the number of patients treated by extracorporeal immunoadsorption remains small due to a lack of well-defined controlled trials and limited reimbursement. This review highlights the immunological and technical basis for extracorporeal immunoadsorption, as well as its current status in the treatment of immunologically-mediated diseases.

Management of patients with chronic, refractory idiopathic thrombocytopenic purpura

Chronic refractory idiopathic thrombocytopenic purpura (ITP) is defined as ITP with persistent thrombocytopenia despite conventional initial management with prednisone and splenectomy. Rare in children, It may occur in as many as one third of adults with ITP. The goal of treatment is not cure of the ITP, but only to achieve a safe platelet count, which is arbitrarily assumed to be greater than 30,000 to 50,000/microL. The risk for major bleeding seems great only when the platelet count is less than 10,000/microL. Treatment of patients with moderate thrombocytopenia and no clinically important bleeding symptoms should be avoided. There is no accepted algorithm for management of patients with chronic refractory ITP. Observation without specific treatment must be considered a cornerstone of management. Combination regimens of Immunosuppressive agents may be required for patients with severe and symptomatic thrombocytopenia. Additional supportive care measures are also important.