IVIG Ameliorates Thrombin Activation of Platelets and Endogenous Thrombin Potential In Pediatric Patients with ITP.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3706-3706
Author(s):  
Sabine Kroiss ◽  
Oliver Speer ◽  
Jeannine Winkler ◽  
Alexandra Förderer ◽  
Markus Schmugge
Keyword(s):  
Platelet Count ◽  
Platelet Function ◽  
Surface Expression ◽  
Ivig Treatment ◽  
Healthy Children ◽  
Platelet Surface ◽  
Platelet Counts ◽  
Before And After ◽  
Healthy Control ◽  
Thrombin Activation

Abstract Abstract 3706 Immune thrombocytopenia (ITP) is a common hematological disorder in children that can lead to severe bleeding symptoms. Previous studies in ITP patients have found autoantibodies that bind to glycoprotein (GP) complex GPIIb/IIIa or GPIb/IX (Kiefel V et al. Br J Hematol 1991) and thus can alter platelet function (Olsson A et al. Thromb Res 2002; Nissner H et al. Blood 1986). Although platelet function has been studied in chronic ITP and in pediatric ITP (Panzer S et al. Europ J Haemat 2007; Semple et al. Blood 1996), so far platelet function was not studied in response to IVIg treatment, which leads to an increase of platelet counts and reduced bleeding symptoms. Next to platelet count no other biological markers have been correlated to bleeding symptoms. Therefore we studied the effect of IVIg treatment on platelet function and endogenous thrombin potential (ETP) in children with newly diagnosed primary ITP. Bleeding symptoms were assessed according to a pediatric bleeding score for ITP at the time of diagnosis and venous blood samples were obtained at the time of diagnosis and after IVIg therapy for measurement of platelet count and for flow cytometric analyses of platelets. In citrated platelet-rich plasma platelets were identified as CD42 positive events; CD62p, CD63 and PAC-1 binding were measured as % platelets with bound fluorescence before and after thrombin stimulation. All patients (median age 6.5 yrs, n=18) presented with typical symptoms of acute ITP with bleeding scores of 2 – 3 and had platelet counts < 20×109/L. (fig. 1). Results from ITP patients were compared to healthy children (median age 6.8 yrs, n = 18) with normal platelet counts and to children with thrombocytopenia as a result of chemotherapy for malignancies (cTP; median age 10.2 yrs, n = 9; platelet counts of 3 – 51×109/L). Results were expressed as the % of platelets expressing the antigen and were analyzed by ANOVA and Wilcoxon test. At initial presentation platelets of ITP patients showed an increased surface expression of CD62p (mean ± SEM: 14.4 ± 3.7 %, n = 17; p<0.05) and CD63 (27.21 ± 5.35 %, n = 17; p<0.05) compared to platelets from cTP patients (3.7 ± 1.1; 9.29 ± 1.7 %, n = 9) and healthy controls (4.9 ± 1.4; 9.5 ± 2.2 %, n = 9). PAC-1 binding was not increased in any of these groups. After thrombin stimulation, platelet surface expression of CD62p, CD63 and PAC1 increased significantly (p<0.0001). Among the groups, thrombin-stimulated expression of CD62p, CD63 and PAC1 was reduced in ITP (55.75 ± 7.77%; 57.07 ± 7.97%; 30.73 ± 7.71%; p<0.01) and in cTP (51.76 ± 7.59%; 55.22 ± 10.71%; 15.51 ± 5.05%; p<0.001) compared to healthy children (84.36 ± 4%; 91.94 ± 1.82%; 69.15 ± 6.91%). ETP was reduced in both, ITP (179.2 ± 52.3 nM thrombin; p<0.01) and cTP (185.0 ± 101.6 nM; p<0.05) compared to healthy children (353.4 ± 33.3 nM). After IVIg treatment all ITP patients showed a rise in platelet counts to >= 20 × 109/L (mean 46 × 109/L, range 20 – 123 × 109/L) and amelioration of bleeding symptoms. Concomitantly thrombin-stimulated platelet surface expression of CD62p, CD63 and PAC1 (84.51 ± 5.04%; 85.32 ± 5.79%; 56.8 ± 7.88%; p range 0.3 – 0.6) and ETP (316.6 ± 48.3 nM; p=0.3) improved and were not different from results in healthy children. In summary we demonstrated that platelets of children with primary ITP at baseline show an increased CD62p surface expression while thrombin-stimulated platelet activation of ITP and cTP patients is decreased compared to healthy children. After IVIg thrombin-stimulated platelet activation and ETP is similar to that seen in healthy children, even before normalization of the platelet counts. Figure 1. Pediatric ITP patients show increased proportions of platelets with p-selectin exposure and a decreased thrombin activation, which is normalized after IVIg treatment independent of the platelet count. (A) Platelet counts (Tc count), (B) proportion of platelets exposing p-selectin (% CD62p+ platelets) without and (C) with thrombin-stimulation (+ thrombin) were compared between children with ITP before and after IVIg treatment (ITP+IVIg), healthy control and cTP. The median and upper and lower quartiles are shown in boxes with whiskers for the range of data and open symbols for outliners. Figure 1. Pediatric ITP patients show increased proportions of platelets with p-selectin exposure and a decreased thrombin activation, which is normalized after IVIg treatment independent of the platelet count. (A) Platelet counts (Tc count), (B) proportion of platelets exposing p-selectin (% CD62p+ platelets) without and (C) with thrombin-stimulation (+ thrombin) were compared between children with ITP before and after IVIg treatment (ITP+IVIg), healthy control and cTP. The median and upper and lower quartiles are shown in boxes with whiskers for the range of data and open symbols for outliners. Disclosures: No relevant conflicts of interest to declare.

Association Of Platelet Function Markers, Independent Of Platelet Count, With Bleeding Score In Patients With Immune Thrombocytopenia

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3534-3534
Author(s):  
Andrew L. Frelinger ◽  
Anja J Gerrits ◽  
Michelle A. Berny-Lang ◽  
Travis Brown ◽  
Sabrina L. Carmichael ◽  
...  
Keyword(s):  
Platelet Count ◽  
Platelet Activation ◽  
Platelet Function ◽  
Research Funding ◽  
Immune Thrombocytopenia ◽  
Univariate Analysis ◽  
Blood Draw ◽  
Platelet Surface ◽  
Platelet Counts ◽  
Bleeding Score

Abstract Background Immune thrombocytopenia (ITP) patients with similarly low platelet counts differ in their tendency to bleed. Aim To determine if differences in platelet function in ITP patients with similarly low platelet counts partly account for the variation in bleeding tendency. Methods The relationship between bleeding scores and platelet function markers was investigated in a single center cross-sectional study of pediatric patients with ITP. Following informed consent, blood was collected from ITP patients and bleeding was graded using the Buchanan and Adix Score (J Pediatr 2002) at routine clinic visits or while admitted to the hospital. Bleeding scores were obtained by one of three hematologists blinded to platelet function results, and investigators performing platelet function tests were blinded to clinical results. Platelet function was assessed by whole blood flow cytometric measurement of unstimulated, ADP- or TRAP-stimulated platelet surface activated GPIIb-IIIa (as measured by PAC1 binding), P-selectin, and GPIb and by unstimulated, convulxin-, or ADP plus TRAP-stimulated platelet surface phosphatidylserine expression (as determined by annexin V binding). Platelet count, immature platelet fraction (IPF) and mean platelet volume (MPV) were determined by a Sysmex XE-2100, and platelet forward angle light scatter (FSC) was measured by flow cytometry. Results Platelet function and bleeding scores were evaluated in 34 consecutive consenting pediatric ITP patients (16 female, 18 male, age 9.7 ± 5.7 years [mean ± SD]). ITP was newly diagnosed (< 3 months) in 10 patients, persistent (3 -- 12 months) in 7 patients, and chronic (>12 months) in 17 patients. Platelet count at the time of the blood draw was 47 ± 55 x 109/L. The median bleeding score on day of blood draw was 1 (range 0 to 4). By univariate analysis, higher IPF, and lower platelet count were significantly associated with a higher bleeding score (odds ratio [OR] >1, p<0.05) but MPV was not. Multiple measures of platelet function were associated with bleeding scores by univariate analysis: higher levels of platelet FSC (a measure affected by multiple variables including size) surface GPIb on unstimulated, ADP- or TRAP-stimulated platelets, surface P-selectin on unstimulated platelets, and platelet FSC were associated with increased odds for higher bleeding scores (ORs each >1, p<0.05), while higher ADP- and TRAP-stimulated platelet surface activated GPIIb-IIIa and P-selectin were associated with reduced odds of higher bleeding scores (ORs each <1, p<0.05). After adjustment for platelet count, higher levels of platelet surface P-selectin on unstimulated platelets, GPIb on TRAP-stimulated platelets, and FSC remained significantly associated with increased odds for higher bleeding scores (Figure), but IPF did not. Similarly, after adjustment for platelet count, higher TRAP-stimulated percentage of P-selectin and activated GPIIb-IIIa positive platelets remained significantly associated with reduced odds of higher bleeding scores (Figure). These findings were independent of recent ITP-related treatment. Conclusions In this study of pediatric ITP patients, we identified selected platelet function markers which, independent of platelet count, are associated with increased (platelet FSC, platelet surface P-selectin on unstimulated platelets, and GPIb on TRAP-stimulated platelets) or decreased (TRAP-stimulated percent P-selectin and GPIIb-IIIa positive platelets) odds of high bleeding scores. Possible hypotheses to explain these associations are as follows: 1) Increased P-selectin on unstimulated platelets demonstrates in vivo platelet activation, possibly as a consequence of the recent bleeding. 2) Because platelet activation results in a reduction in platelet surface GPIb and increases in platelet surface activated GPIIb-IIIa and P-selectin, the ORs associated with all of these markers could be explained by reduced ability of platelets in patients with higher bleeding scores to respond to agonists. 3) While platelet FSC is partly related to size, the finding that MPV and IPF, adjusted for platelet count, were not associated with bleeding score suggests that factors other than size account for the association of platelet FSC with higher bleeding scores. Further study is required to validate these findings and determine if differences in platelet function are associated with future risk for bleeding. Disclosures: Off Label Use: Eltrombopag was given to WAS/XLT patients for treatment of thrombocytopenia. Neufeld:Shire: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Apopharma: Consultancy. Michelson:Sysmex: Honoraria.

An evaluation of methods for determining reference intervals for light transmission platelet aggregation tests on samples with normal or reduced platelet counts

2008 ◽  
Vol 100 (07) ◽  
pp. 01-12 ◽  
Author(s):  
Karen A. Moffat ◽  
Menaka Pai ◽  
Yang Liu ◽  
Jodi Seecharan ◽  
Heather McKay ◽  
...  
Keyword(s):  
Platelet Count ◽  
Platelet Aggregation ◽  
Platelet Function ◽  
Light Transmission ◽  
Reference Intervals ◽  
Platelet Counts ◽  
Healthy Control ◽  
Parametric Analyses ◽  
Control Samples ◽  
Non Parametric

SummaryLight transmission platelet aggregation tests are important for diagnosing platelet function defects. However, uncertainties exist about the best procedures to determine aggregation reference intervals. We investigated methods for determining reference intervals for light transmission aggregation tests, using the % maximal aggregation values for prospectively collected data on healthy control samples. Reference intervals for samples tested at 250 x 109 platelets/l were determined by mean ± 2 standard deviations and non-parametric analyses. To establish reference intervals for tests on thrombocytopenic subjects, regression analyses were used to estimate 95% confidence limits for % maximal aggregation, according to sample platelet counts, using data for control samples diluted to match the platelet count of undiluted thrombocytopenic patient platelet-rich plasma samples. For samples tested at 250 x 109 platelets/l, non-parametric analyses described 95% of data for healthy control samples better than mean ± 2 standard deviations. For samples tested at lower counts, to match thrombocytopenic samples, the % maximal aggregation was influenced by platelet count and derived limits were wider at very low platelet counts for almost all agonists. With ristocetin, it proved feasible to test samples with very low platelet counts to exclude Bernard-Soulier syndrome and type 2B von Willebrand disease. Non-parametric analyses should be the preferred method to establish light transmission aggregation reference intervals for samples tested at normal platelet counts. The derived limits for thrombocytopenic samples provide guidance for evaluating thrombocytopenic platelet function disorders, including which agonists to test, based on the sample platelet count.

Post-DDAVP Thrombocytopenia in Type 2B von Willebrand Disease Is not Associated with Platelet Consumption: Failure to Demonstrate Glycocalicin Increase or Platelet Activation

1999 ◽  
Vol 81 (02) ◽  
pp. 224-228 ◽  
Author(s):  
A. Steffan ◽  
E. Pontara ◽  
A. Zucchetto ◽  
C. Rossi ◽  
L. De Marco ◽  
...  
Keyword(s):  
Platelet Count ◽  
Platelet Activation ◽  
Surface Expression ◽  
Von Willebrand Disease ◽  
Platelet Surface ◽  
Platelet Counts ◽  
Normal Platelet ◽  
Thrombotic Complications ◽  
Von Willebrand ◽  
Willebrand Factor

SummaryThrombocytopenia is frequently reported in type 2B von Willebrand disease (vWD), and thought to be related to the abnormally high affinity of 2B von Willebrand factor (vWF) for platelet GPIb-IX. To gain an insight into the nature of this thrombocytopenia, we measured plasma glycocalicin (GC) levels (as a marker of platelet turnover), and platelet surface expression of the alpha granule protein P-selectin (as a marker of platelet activation) in 9 patients with type 2B vWD before, and in 4 patients also following the infusion of 1-desamino-8-d-arginine vasopressin (DDAVP). Three patients presented a persistent decrease of platelet counts in the resting condition. GC levels were within the normal range, regardless of the platelet counts, in all but one patient who presented, on the other hand, a normal platelet count. Moreover, platelets expressed normal amounts of P-selectin on their surface, regardless of platelet counts. These findings suggest that the thrombocytopenia observed in type 2B vWD is not due to platelet activation and subsequent consumption in circulation.Despite a significant, albeit transient, decrease in platelet count, DDAVP did not induce an increase in plasma GC levels, nor enhance P-selectin expression. These observations indicate that the acute post-DDAVP thrombocytopenia in type 2B vWD is not related to platelet activation and consumption. We advance that the post-DDAVP 2B vWF is hemostatically more active, and able to induce agglutination but not aggregation of circulating platelets. This would explain both the prompt recovery of basal platelet counts after the post-DDAVP decrease, and the lack of reported thrombotic complications in this disorder.Therefore, even though 2B vWF is characterized by an enhanced affinity for the platelet surface, its binding to platelet GPIb-IX in the soluble phase is not able to induce true platelet aggregation; vWF thus appears to be mainly an adhesive protein, rather than an aggregating agent.

Platelet Function and Response to Thrombopoietin Mimetics In Wiskott-Aldrich Syndrome/X-Linked Thrombocytopenia.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1429-1429 ◽  
Author(s):  
James B. Bussel ◽  
Andrew L Frelinger ◽  
William B Mitchell ◽  
Mariana P Pinheiro ◽  
Marc R Barnard ◽  
...  
Keyword(s):  
Platelet Function ◽  
Research Funding ◽  
Annexin V ◽  
Surface Expression ◽  
Platelet Surface ◽  
Wiskott Aldrich Syndrome ◽  
Platelet Counts ◽  
Equity Ownership ◽  
Collagen Receptor ◽  
Normal Controls

Abstract Abstract 1429 Introduction: Wiskott-Aldrich syndrome (WAS) is a complex disease in which patients suffer from both bleeding and immunodeficiency. Thrombocytopenia is severe, platelets are small and may be dysfunctional; intracranial hemorrhage occurs in 20% of patients. In patients with the full WAS phenotype, early use of human stem cell transplantation (HSCT) corrects the immune deficiency and thrombocytopenia although platelet transfusions are often required. Bleeding is the main complication of the X-linked thrombocytopenia (XLT) form, whose management may include HSCT, splenectomy, or supportive care; IVIG has limited benefit. Platelet function in WAS/XLT patients with low platelet counts has not been reported because of the inability to accurately perform standard assays in severely thrombocytopenic patients. The present study evaluated platelet function and thrombopoietin (TPO) mimetic (romiplostim or eltrombopag) treatment of thrombocytopenia in patients with WAS/XLT. Methods: Flow cytometry, which enables evaluation of platelet function despite thrombocytopenia, was used to study platelets in 8 WAS/XLT patients and age-matched normal controls. Platelet function was measured by: surface expression of P-selectin and activated GPIIb-IIIa (reported by PAC1) in whole blood following stimulation with low and high dose ADP and thrombin receptor activating peptide (TRAP); annexin V binding, a marker of platelet surface expression of the procoagulant phospholipid phosphatidylserine, in platelet-rich plasma (normalized to 30,000 platelets/μL) following stimulation with convulxin (a specific agonist of the platelet collagen receptor GPVI). The effects of romiplostim (10 μg/kg/wk SQ) or eltrombopag (50-75 mg/day PO) on platelet counts and bleeding were evaluated in 4 patients (3 WAS, 1 XLT). Results: Platelets from WAS/XLT patients showed reduced TRAP-induced platelet surface P-selectin and activated GPIIb-IIIa (p <0.05) compared to age-matched control children (Figure). In contrast, convulxin-induced annexin V binding to platelets was greater than normal controls (p <0.05). These findings were observed in both WAS and XLT platelets and in non-splenectomized (6) and splenectomized (2) patients. As expected, platelet size of WAS/XLT platelets, as judged by forward light scatter, was smaller than that of normal controls. Two infants were treated with romiplostim and 2 older patients were treated with eltrombopag. One infant had 2 intervals of approximately 1 month each in which his platelets were supported entirely by romiplostim and maintained >20-30,000/μL. However, at times of infection with prolonged antibiotics, romiplostim was insufficient although it enabled platelet transfusions to be given weekly. In the other infant, who had both WAS-associated and autoimmune thrombocytopenia, romiplostim had no apparent effect; his platelets were only responsive to the combination of IVIG/methylprednisolone plus platelet transfusion given 2–3 times weekly prior to HSCT. A 25 year old XLT patient received eltrombopag for 4 weeks with a platelet increase from 18 to 33,000/μL. A fourth patient, with WAS, who had failed HSCT was treated with eltrombopag without consistent success. In the first infant on romiplostim and the XLT patient on eltrombopag, clinical bleeding was reduced in conjunction with the increased platelet count. Conclusions: Bleeding in WAS/XLT may be the result of both platelet dysfunction and thrombocytopenia. WAS/XLT platelets are smaller and express less surface P-selectin and less activated GPIIb-IIIa in response to TRAP stimulation than age-matched controls. However, WAS/XLT platelets, when stimulated via the collagen receptor GPVI, express more phosphatidylserine, which supports formation of the prothrombinase complex, than control platelets. The reduced platelet function in WAS/XLT patients resulting from reduced platelet number, size, and surface P-selectin and activated GPIIb-IIIa may be counterbalanced in part by increased GPVI-mediated procoagulant activity. However, increased platelet procoagulant activity may shorten platelet lifespan, contributing to the thrombocytopenia in WAS/XLT. Platelet counts were increased and clinical bleeding was decreased in 2 of 4 WAS/XLT patients treated with TPO mimetics. The possible use of TPO mimetics to increase platelet count and/or function in WAS/XLT patients merits further study. Disclosures: Bussel: Portola: Consultancy; Eisai: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; GlaxoSmithKline: Consultancy, Equity Ownership, Research Funding, Speakers Bureau; Amgen Inc.: Equity Ownership, Research Funding, Speakers Bureau; Cangene: Research Funding; Genzyme: Research Funding; Immunomedics: Research Funding; Ligand: Research Funding, Speakers Bureau; Shionogi: Research Funding, Speakers Bureau; Sysmex: Research Funding. Off Label Use: romiplostim and eltrombopag; increase platelet counts in Wiskott-Aldrich syndrome/X-linked thrombocytopenia patients. Michelson:GlaxoSmithKline: Honoraria.

Effects Of Eltrombopag On Thrombocytopenia, Platelet Function and Bleeding In Patients With Wiskott-Aldrich Syndrome/X-Linked Thrombocytopenia

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3536-3536
Author(s):  
Anja J Gerrits ◽  
Emily Leven ◽  
Andrew L. Frelinger ◽  
Michelle A. Berny-Lang ◽  
Hannah Tamary ◽  
...  
Keyword(s):  
Platelet Count ◽  
Board Of Directors ◽  
Platelet Function ◽  
Research Funding ◽  
Annexin V ◽  
Surface Expression ◽  
Advisory Committees ◽  
Platelet Surface ◽  
Platelet Size ◽  
Equity Ownership

Abstract Introduction Patients with Wiskott-Aldrich syndrome (WAS) including X-linked thrombocytopenia (XLT) have microthrombocytopenia, and hemorrhage is a major problem. Current management options in WAS/XLT patients include splenectomy, human stem cell transplant (HSCT) and gene therapy. In this study, we asked whether eltrombopag, a thrombopoietin mimetic, would increase platelet counts, improve platelet function, and/or reduce bleeding in WAS/XLT patients. Methods In 9 WAS/XLT patients and 8 age-matched healthy control subjects, flow cytometry was used to assess platelet function by surface expression of activated GPIIb-IIIa (reported by PAC1) and P-selectin in whole blood after stimulation with low and high concentrations of ADP or thrombin receptor activating peptide (TRAP), and by annexin V binding (a measure of surface phosphatidylserine) in platelet-rich plasma after stimulation with convulxin. Eltrombopag was administered to 5 WAS and 3 XLT patients (50 mg in 2 adults, and 1 mg/kg in 6 children up to 75 mg/day) with a goal platelet count ≥50k. Results High concentration ADP- or TRAP-induced PAC1 mean fluorescence intensity (MFI) was significantly reduced in WAS/XLT patients compared to healthy controls (Figure). Platelet surface P-selectin MFI in response to TRAP was also significantly reduced. In contrast, annexin V binding to platelets was not different between WAS/XLT and controls. As expected, platelet size of WAS/XLT patients was smaller than controls. WAS protein (which is deficient in WAS/XLT), is important for cytoskeletal movement and could therefore be involved in trafficking of surface proteins. However, surface expression of activated GPIIb-IIIa and P-selectin were no longer different in WAS/XLT patients vs. controls when corrected for size by platelet surface CD41 MFI. In 3 WAS/XLT patients whose platelet count improved on eltrombopag, platelet function did not improve. The table summarizes the results of eltrombopag treatment in 5 responders (2 WAS, 3 XLT patients) and 3 non-responders (3 WAS patients). Comparison of baseline, peak and change in immature platelet fraction in 5 WAS/XLT responders to eltrombopag vs. 7 pediatric chronic immune thrombocytopenia (ITP) patients responding to eltrombopag showed a significant decrease in all three measures, suggesting that platelet production in WAS/XLT patients is more difficult to increase than in ITP patients. Long term eltrombopag use in WAS/XLT patients showed no tachyphylaxis, transaminitis or induction of malignancy. Conclusions 1) Baseline platelet function in WAS/XLT is reduced compared to healthy age-matched controls, as measured by agonist-induced platelet surface activated GPIIb-IIIa and P-selectin. 2) This reduction is proportional to the reduced platelet size in WAS/XLT compared to controls. 3) In contrast, annexin V binding (a measure of platelet procoagulant activity) showed no differences between WAS/XLT and controls. 4) Eltrombopag has beneficial effects on the thrombocytopenia and bleeding, but not platelet function, in the majority of WAS/XLT patients. 5) This eltrombopag-induced reduction in bleeding is presumably primarily the result of the increased platelet count, but it was also observed in 2 eltrombopag “non-responders” (i.e. patients whose platelet counts did not increase after eltrombopag). 6) The production of new platelets with eltrombopag is less in WAS/XLT than in ITP. Disclosures: Off Label Use: Eltrombopag was given to WAS/XLT patients for treatment of thrombocytopenia. Michelson:Sysmex: Honoraria. Bussel:GlaxoSmithKline: Equity Ownership, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Amgen: Equity Ownership, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Cangene: Research Funding; Genzyme: Research Funding; IgG of America: Research Funding; Immunomedics: Research Funding; Ligand: Membership on an entity’s Board of Directors or advisory committees, Research Funding; Eisai: Membership on an entity’s Board of Directors or advisory committees, Research Funding; Shionogi: Membership on an entity’s Board of Directors or advisory committees, Research Funding; Sysmex: Research Funding; Symphogen: Membership on an entity’s Board of Directors or advisory committees.

Determination and Treatment of Disorders of Primary Haemostasis

1999 ◽  
Vol 19 (04) ◽  
pp. 168-175 ◽  
Author(s):  
M. Weippert-Kretschmer ◽  
V. Kretschmer
Keyword(s):  
Platelet Function ◽  
Bleeding Risk ◽  
Bleeding Complications ◽  
Bleeding Tendency ◽  
Platelet Counts ◽  
Platelet Function Disorders ◽  
Perioperative Bleeding ◽  
Before And After ◽  
Low Sensitivity

SummaryPerioperative bleeding complications due to disorders of primary haemostasis are often underestimated. Routine determination of primary haemostasis is still problematic. The in vivo bleeding time (BT) shows low sensitivity and high variability. In this contribution the results and experiences with the IVBT having been obtained in various studies and during 10 years of routine use are reported. Patients and Methods: Blood donors before and after ASA ingestion, patients with thrombocytopenia as well as congenital and acquired platelet function disorders. Monitoring of desmopressin efficacy. IVBT with Thrombostat 4000 (tests with CaCl2 = TST-CaCl2 and ADP = TST-ADP) and PFA-100 (test cartridges with epinephrine = PFA-EPI and ADP = PFA-ADP). Results and Conclusions: IVBT becomes abnormal with platelet counts <100,000/μl. With platelet counts <50,000/μl the results are mostly outside the methodical range. IVBT proved clearly superior to BT in von Willebrand syndrome (vWS). All 16 patients with vWS were detected by PFA-EPI, whereas with BT 7 of 10 patients with moderate and 1 of 6 patients with mild forms of vWS were spotted. The majority of acquired and congenital platelet function disorders with relevant bleeding tendency were detectable by IVBT. Sometimes diagnostic problems arose in case of storage pool defect. Four to 12 h after ingestion of a single dose of 100 mg ASA the TST-CaCl2 became abnormal in all cases, the PFA-EPI only in 80%. However, the ASA sensitivity of TST-CaCl2 proved even too high when looking for perioperative bleeding complications in an urological study. Therefore, the lower ASS sensitivity of the PFA-100 seems to be rather advantageous for the estimation of a real bleeding risk. The good efficacy of desmopressin in the majority of cases with mild thrombocytopenia, congenital and acquired platelet function disorders and even ASS-induced platelet dysfunction could be proven by means of the IVBT. Thus IVBT may help to increase the reliability of the therapy. However, the IVBT with the PFA-100 is not yet fully developed. Nevertheless, routine use can be recommended when special methodical guidelines are followed.

Influence of platelet count on the expression of platelet collagen receptor glycoprotein VI (GPVI) in patients with acute coronary syndrome

2009 ◽  
Vol 101 (05) ◽  
pp. 911-915 ◽  
Author(s):  
Boris Bigalke ◽  
Konstantinos Stellos ◽  
Dimitrios Stakos ◽  
Thomas Joos ◽  
Oliver Pötz ◽  
...  
Keyword(s):  
Acute Coronary Syndrome ◽  
Platelet Count ◽  
Thrombus Formation ◽  
Surface Expression ◽  
Platelet Surface ◽  
Glycoprotein Vi ◽  
Coronary Syndrome ◽  
Symptomatic Coronary Artery Disease ◽  
Artery Disease ◽  
Collagen Receptor

SummaryPlatelets play a key role in the development of an acute coronary syndrome (ACS) and contribute to cardiovascular events. Platelet collagen receptor glycoprotein VI (GPVI) contributes significantly to platelet adhesion and thrombus formation in ACS. We consecutively investigated both the platelet count and the platelet surface expression of GPVI in 843 patients with a symptomatic coronary artery disease verified by coronary angiography. Four hundred fourteen patients presented with stable angina pectoris and 429 patients with ACS. Platelet surface expression of GPVI and CD62P was determined by flow cytometry and platelet count with a coulter counter, plasmatic soluble GPVI was measured by ELISA. Platelet GPVI expression in patients with ACS was compared to platelet count. Patients with ACS showed significantly elevated GPVI expression levels in the first and second quartiles of platelet count compared to patients with higher platelet count [mean fluorescence intensity (MFI) ± standard deviation): 1st vs. 4th: 20.44 ± 6.1 vs. 18.62 ± 3.7; p=0.012; 2ndvs.3rd:21.2±8.5vs.18.76±3.7;P=0.03; 2ndvs.4th: 21.2±8.5vs.18.62±3.7;P=0.004], which was paralleled in trend for the CD62P expression [MFI: 1st vs. 4th: 11.2 ± 6.8 vs. 12.3 ± 9; p=0.057; 2nd vs. 3rd: 16.3 ± 16 vs.12.7 ± 5.3; p=0.138; 2nd vs. 4th: 16.3 ± 16 vs.11 ± 4.4; p=0.043]. In a subgroup of 48 patients with ACS, determination of soluble GPVI showed similar results [plasma GPVI (ng/ml): 1stvs.4th: 1.6 ± 0.6 vs. 1.2 ± 0.4; p=0.046; 1st vs. 3rd: 1.6 ± 0.6 vs. 1.1 ± 0.5; p=0.038; 2nd vs. 3rd: 1.9 ± 0.8 vs. 1.1 ± 0.5; p=0.04; 2nd vs. 4th: 1.9 ± 0.8 vs. 1.2 ± 0.4; p=0.056]. Thus, a lower platelet count comes along with a higher GPVI surface expression and plasma concentration in patients with ACS, which potentially reflects increased activation and enhanced recruitment of platelets to the site of vascular injury.

Effect Of Prednisone On Platelet Function In Patients With Bleeding Disorders

1981 ◽  
Author(s):  
R McKenna ◽  
F Bachmann ◽  
O Pichairut ◽  
B Whittaker
Keyword(s):  
Platelet Count ◽  
Platelet Function ◽  
Bleeding Time ◽  
Platelet Factor ◽  
Von Willebrand's Disease ◽  
Von Willebrand’S Disease ◽  
Before And After ◽  
History Of ◽  
The Mean ◽  
One Year

There is considerable controversy regarding the effect of Prednisone on the hemostatic mechanism of normal people versus patients with bleeding diatheses. We administered Prednisone 15 mg TID to patients with a positive history of a bleeding disorder, and evaluated the bleeding time and other in-vitrc tests of platelet function prior to and between the 5th and 7th day after Prednisone.Eleven patients were admitted into this study over a one year period. All patients had a history of excessive bruising, epistaxis, bleeding after dental extractions, and gastrointestinal or other bleeding in various combinations. Two out of the eleven had template bleeding times of greater than 15 minutes both before and after the Prednisone. These two patients were subsequently proven to have von Willebrand’s disease by the washed platelet ristocetin assay. In the remaining 9 patients, the pre-Prednisone bleeding time was 9.3 ±3.7 minutes (x ± 1 S.D.) whereas the post-Prednisone bleeding time was 5.8 ±3.6 minutes (x ±1 S.D.). These results were significant(td=3.83;df:7;p=0.007).Platelet aggregation in response to exogenous ADP (1 μM, 3 μM) Sigma bovine tendon collagen (1.8 mg/ml F) and epinephrine (5.5 × 104M), platelet retention in a glass bead column or platelet factor 3 availability did not improve or worsen after Prednisone therapy. The mean platelet count of 328,000±94,000 (x ±1 S.D.) was significantly (p=0.05) higher than the mean pre-Prednisone platelet count of 268,000±77,000 (x ±1 S.D.).In conclusion, we have shown that large doses of Prednisone appear to shorten the bleeding time in patients with significant defects in the primary hemostatic mechanism. However the bleeding time improvement is not evident in patients with von Willebrand’s disease.

Changes in Platelet Function and Platelet Counts During Substitution Therapy in Haemophiliacs and Produced by Plasmapheresis in Patients Suffering from Inhibitors

1979 ◽  
Author(s):  
E. Dumitrescu ◽  
I. Ambrus ◽  
Kh. Nienhaus ◽  
B. Podolsak ◽  
E. Wenzel
Keyword(s):  
Factor Viii ◽  
Platelet Function ◽  
Clinical Signs ◽  
Bleeding Complications ◽  
Substitution Therapy ◽  
Drug Induced ◽  
Platelet Counts ◽  
Before And After ◽  
Factor Viii Concentrates ◽  
Laboratory Investigations

We noticed a systematic increase in small platelets (evaluated by electronical analysis of platelet volune distribution, using the Coulter Counter equipment, Wenzel 1977) during substitution therapy in patients suffering from haemophilia (N = 60). Laboratory investigations on these patients were performed before substitution and then 30 min., 60 min., 120 min. and 24 hours after infusion of factor-VIII-concentrationa (Inmuno, Schwab, Behring, factor-VIII-concentrates 20 U/kg b.w.). The same investigations were performed before and after plasmapheresis using a Hemonetric cell separator (N = 7}. in 48 of the patients, the clinical signs were insignificant (bleeding time, according to Duke, was found to be normall, although the platelet changes ware considerable (decrease in platelet count and increase of the percentage of platelets smaller than 4.5 μ3). However, significant test results were noticed in a haemophiliac patient suffering from inhibitory- and drug-induced platelet disorders during and after plasmapheresis. We observed bleeding complications only in 2 cases (Duke; 7 min. and 9 min.). Yet, a coneiderable decrease in platelet counts was observed as well as a significant increase in the percentages of small platelets (4.5 μ3, N = 48) in all cases. Controlling platelet function in haemophiliacs following substitution therapy could be essential as well as controlling the usual hemolysis parameters after plasmapheresis.

Analysis of Platelet Receptor Expression in ITP,

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 3289-3289
Author(s):  
Jianlin Qiao ◽  
Huy Tran ◽  
Fi-Tjen Mu ◽  
Robert K Andrews ◽  
Elizabeth E Gardiner
Keyword(s):  
Platelet Count ◽  
Conflicts Of Interest ◽  
Surface Expression ◽  
Experimental Models ◽  
Receptor Expression ◽  
Response To Treatment ◽  
Platelet Surface ◽  
Healthy Donors ◽  
Platelet Receptor ◽  
Von Willebrand

Abstract Abstract 3289 In this study we assess platelet receptor expression and shedding in patients with immune thrombocytopenia (ITP) before and during treatment. The aim is to evaluate the potential value of quantitative measurement of platelet receptors for diagnosis and/or monitoring treatment in thrombocytopenia due to immune or other causes. The platelet-specific collagen receptor, glycoprotein (GP)VI, is associated with the Fc receptor γ-chain (FcRγ). GPVI/FcRγ is coassociated on platelet surface with the GPIb-IX-V complex; GPIbα of GPIb-IX-V binds von Willebrand factor and other ligands. Our previous studies showed engagement of platelet FcγRIIa by antiplatelet antibodies induced ectodomain shedding of GPVI, generating soluble ectodomain (sGPVI) in plasma. However, apart from one individual with an anti-GPVI antibody, whether anti-platelet antibodies associated with ITP affect GPVI/GPIb expression/shedding has not been addressed. In this study we used flow cytometry and a sGPVI ELISA to assess 1) whether patients with ITP had dysregulated expression/shedding of GPVI or GPIbα, and 2) whether platelet receptor expression changes prior to recovery of platelet count in individuals undergoing treatment for ITP. In 9 ITP patients (mean age=48.6, range 29–79; 6 female) with platelet count 61±9 × 109/L (range, 33–122 × 109/L), GPVI surface expression (GeoMean±SE, 137±17) was lower than healthy controls (274±26; n=17; platelet count 247±13), and sGPVI in patient plasma was significantly higher (39±4 ng/mL) compared to 17 healthy donors (19±3 ng/mL) (P=0.0006). In longitudinal samples analysed at weekly intervals during 2-month treatment with steroids, decreased GPVI surface expression and increased sGPVI in plasma remained essentially unchanged as the platelet count normalized, consistent with persistent anti-platelet antibody. However, while levels of intact platelet GPIbα were significantly reduced in ITP compared to healthy donors (P=0.0053), they approached healthy levels within 1 week of treatment, preceding improvement in platelet count or other measures. GPIbα expression/cleavage has been previously implicated in platelet clearance in experimental models, and our analysis suggests the proteolytic status of human GPIbα may be a novel early marker for evaluating response to treatment in ITP. Disclosures: No relevant conflicts of interest to declare.

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