Evaluation of Children with Suspected Bleeding Disorder Applying the Impact-R [Cone and Plate(let) Analyzer].

Abstract Background: von Willebrand’s disease (VWD) is the most common bleeding disorder, affecting between 1–10% of the general population. There is a need for a simple test to screen patients with bleeding symptoms before more labor-intensive diagnostic steps are taken. The Impact-R [Cone and Plate(let) Analyzer (CPA)] (DiaMed Switzerland), was designed in an attempt to test platelet function under close to physiological conditions. Citrated whole blood is applied on polystyrene surface, under controlled shear conditions using a cone and plate device, followed by a quantitative analysis of platelet deposition to immobilized plasma von Willebrand’s factor (VWF) and fibrinogen. Results of the test are presented for adhesion as % surface coverage (SC) and for aggregation as average size (μm2, AS). In this study we report the use of CPA test in evaluation of children with suspected bleeding disorder. Methods: Fifty-four consecutive children with bleeding symptoms and normal platelet count and coagulation tests were evaluated between August 1st, 2006 and July 31, 2007. In addition to the CPA test, all children were tested for VWF: antigen plasma level, VWF: ristocetin activity, factor VIII: C plasma level, platelet aggregation test using turbidometric aggregometer (Helena, USA) and blood type. The study was approved by the local Helsinki committee. Statistical analysis was done by SPSS. Results: Of 54 children, 10 (18.9%) were diagnosed with VWD and 6 (11.1%) children were diagnosed with platelet function defect according to bleeding history, family history, aggregation and factor VIII/VWF tests. To test the validity of the CPA as a screening test for diagnosis of VWD and platelet function defects a ROC curve was formulated for both SC and AS measurements. The best cutting point for a positive test was equal or less then 6.5% for SC measurement (sensitivity 60%, specificity 65%), and equal or lest then 26.5μm2 for AS measurement (sensitivity 67%, specificity 81.6%). The predictive value of a normal CPA test (negative predictive value), i.e. SC > 6.5% and AS > 26.5μm2, was 92%. Of the 26 normal CPA tests, one child was diagnosed with mild type I VWD and one child was diagnosed with mild platelet defect in response to epinephrine (40%). The predictive value of an abnormal CPA test (positive predictive value) was 50%. Of the 28 abnormal CPA test, 9 children were diagnosed with VWD, 4 children with platelet defect in response to epinephrine (<30%) and one child with platelet defect in response to collagen (10%). Significant bleeding symptoms (bleeding score 3 or more) were reported in 4 of 14 children with abnormal CPA test but with normal VWF, normal factor VIII and normal platelet aggregation. Conclusions: The CPA test was found to be a useful tool for excluding VWD and platelet function defect in children suspected for bleeding disorder. Yet, in case of an abnormal CPA test, further testing are needed. Interestingly, abnormal CPA test was the only finding in some children with a significant bleeding history, suggesting other underlying adhesion defects yet to be described.

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Abstract 2214: The Aptamer ARC1779 Is A Potent And Specific Inhibitor Of von Willebrand Factor (vWF) Mediated Ex Vivo Platelet Function In ST-elevation (STEMI) and non-ST elevation (NSTEMI) Acute Myocardial Infarction (AMI)

Circulation ◽

10.1161/circ.116.suppl_16.ii_481-b ◽

2007 ◽

Vol 116 (suppl_16) ◽

Author(s):

Bernd Jilma ◽

Florian B Mayr ◽

Alexander O Spiel ◽

Patricia G Merlino ◽

Harold N Marsh ◽

...

Keyword(s):

Platelet Aggregation ◽

Platelet Function ◽

Platelet Adhesion ◽

Ex Vivo ◽

Specific Inhibitor ◽

Citrate Anticoagulation ◽

St Elevation ◽

A1 Domain ◽

The Impact ◽

Novel Therapeutic

Background: ARC1779 is an aptamer which blocks the A1 domain binding of the vWF A1 domain to platelet GPIb receptors that is now in development for the treatment of AMI. vWF is increased in the elderly and in the setting of AMI, as reflected in higher vWF levels in circulation and in increased shear-dependent platelet function as measured by the platelet function analyzer (PFA-100) and cone and plate analyzer (IMPACT). Conventional therapy of AMI partially reduces platelet activation and aggregation, but does not address excessive vWF activity or platelet adhesion. Methods: We studied the ex vivo dose response curves for ARC1779 on PFA-100 and IMPACT platelet function tests, agonist-induced platelet aggregation, and vWF activity (free A1 domain sites) of patients with AMI on standard treatment including aspirin and clopidogrel (n=40), young (n=20) and elderly controls (n=20). Results: ARC1779 fully blocked collagen ADP induced platelet plug formation as measured by PFA-100 with an IC100 of ~ 1–2 mcg/mL with citrate anticoagulation, and 3–5 mcg/mL with hirudin anticoagulation. ARC1779 fully blocked shear-dependent platelet adhesion measured by the IMPACT analyzer with an IC100 of ~ 1 mcg/mL with citrate anticoagulation. In contrast to GPIIb/IIIa antagonists, ARC1779 did not inhibit platelet aggregation by ADP, collagen or arachidonic acid at concentrations (10mcg/mL) that fully inhibited vWF dependent platelet function. ARC1779 fully blocked vWF activity ex vivo with an IC90 of ~ 1 mcg/mL in young controls and 6 – 8 mcg/mL in STEMI and NSTEMI patients. Conclusions: ARC1779 potently and specifically inhibits vWF activity and vWF dependent platelet function, even in the setting of AMI where vWF activity is increased. ARC1779 represents a novel therapeutic principle (vWF antagonism) and a novel therapeutic class (aptamers). Potent and specific inhibition of VWF makes ARC1779 a promising development candidate for patients with AMI. Results

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Platelet Function Disturbance During Veno-Venous ECMO in ARDS Patients Assessed by Multiple Electrode Aggregometry—A Prospective, Observational Cohort Study

Journal of Clinical Medicine ◽

10.3390/jcm8071056 ◽

2019 ◽

Vol 8 (7) ◽

pp. 1056 ◽

Cited By ~ 4

Author(s):

Saskia Wand ◽

Jan Felix Huber-Petersen ◽

Joern Schaeper ◽

Claudia Binder ◽

Onnen Moerer

Keyword(s):

Platelet Aggregation ◽

Platelet Function ◽

Extracorporeal Circulation ◽

Inverse Correlation ◽

Negative Effects ◽

Multiple Electrode Aggregometry ◽

Observational Cohort ◽

And Function ◽

The Impact ◽

Multiple Electrode

Extracorporeal (veno-venous) membrane oxygenation (vvECMO) has been shown to have negative effects on platelet number and function. This study aimed to gain more information about the impact of vvECMO on platelet function assessed by multiple electrode aggregometry (MEA). Twenty patients with the indication for vvECMO were included. Platelet function was analyzed using MEA (Multiplate®) before (T-1), 6 h (T0), one (T1), two (T2), three (T3), and seven (T4) days after the beginning of vvECMO. Median aggregational measurements were already below the normal reference range before vvECMO initiation. Platelet aggregation was significantly reduced 6 h after vvECMO initiation compared to T-1 and spontaneously recovered with a significant increase at T2. Platelet count dropped significantly between T-1 and T0 and continuously decreased between T0 and T4. At T4, ADP-induced platelet aggregation showed an inverse correlation with the paO2 in the oxygenator. Platelet function should be assessed by MEA before the initiation of extracorporeal circulation. Although ECMO therapy led to a further decrease in platelet aggregation after 6 h, all measurements had recovered to baseline on day two. This implies that MEA as a whole blood method might not adequately reflect the changes in platelet function in the later stages of extracorporeal circulation.

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Intracranial Hemorrhage in a Patient with Osteogenesis Imperfecta Due to Inherited and Acquired Platelet Dysfunction.

Blood ◽

10.1182/blood.v108.11.3960.3960 ◽

2006 ◽

Vol 108 (11) ◽

pp. 3960-3960

Author(s):

Arash Rezazadeh ◽

Sandra C. Hollensead ◽

Damian A. Laber ◽

Goetz H. Kloecker

Keyword(s):

Platelet Aggregation ◽

Osteogenesis Imperfecta ◽

Factor Viii ◽

Platelet Dysfunction ◽

Multiple Fractures ◽

Vascular Abnormality ◽

Prolonged Bleeding Time ◽

Normal Platelet ◽

Abnormal Bleeding

Abstract A 42 year-old man with Osteogenesis Imperfecta (OI) had three episodes of spontaneous Subdural Hematoma (SH) after binge drinking. There is no remote history of abnormal bleeding or easy bruising despite multiple fractures. Medications included Aspirin (ASA). The first and second SH occurred within the preceding year and were treated conservatively. The third SH occurred while on ASA and drinking more than 500cc liquor/day. The Platelet Function Assay (PFA-100) was significantly abnormal (see table). After platelet transfusions the SH was surgically evacuated without complications. An MRA of the head showed no vascular abnormality. CBC, serum chemistries, PT, PTT, factor VIII and von Willebrand factor were normal. The patient stopped taking ASA, but continued to drink. The PFA-100, although abnormal, had improved. After a month-long alcohol abstinence his PFA-100 normalized. He has been without SH ever since. However the platelet aggregation study still shows a lack of second wave response to ADP. EVENT ASA ETOH Collagen/Epi Collagen/ADP Platelet Count SH3 (+) (+) >300 112 266 Plt transfusion n/a n/a 122 51 347 Follow up (−) (+) 219 108 231 Follow up (−) (−) 117 80 276 Reference Range 118–162 Seconds 59–103 Seconds 140–370 Discussion: Both OI and ETOH are known factors of causing intrinsic platelet defect. The Framingham Offspring Study showed that alcohol consumption is inversely associated with both platelet activation and aggregation, particularly in men. ETOH is capable of inhibiting collagen induced platelet aggregation, secretion, arachidonate mobilization, and TXA2 formation. Also it has been suggested that intracellular Ca2+ homeostasis and aggregation in platelets are impaired by ethanol through the generation of H2O2 and oxidation of sulphydryl groups. OI causes vascular fragility and intrinsic platelet defect. In one study the most frequent abnormalities were increased capillary fragility (35%), decreased platelet retention (33%) and reduced factor VIII R:Ag (23%). Reduced ristocetin cofactor, deficient platelet aggregation induced by collagen and prolonged bleeding time were less common findings. The combination of vascular, platelet related and plasmatic defects may reflect that OI is a heterogeneous group of disorders with common clinical expression. Conclusion: Patients with OI are at risk for intracranial bleeding due to vascular fragility and intrinsic platelet defect. Our patient had a normal PFA-100, off ASA and ETOH. The platelet aggregation study -a more sensitive test- was able to detect a platelet secretion defect in our patient. The abnormal platelet aggregation study was likely due to his OI, which never caused abnormal bleeding by itself. The additional affect of ASA and ETOH on his platelets led to recurrent episodes of SH. Many OI patients are on NSAID/ASA due to chronic bone pain. Special attention should be paid to alcohol abuse in this group of patients. Normal platelet counts and coagulation tests may not be sufficient to evaluate the risk of bleeding. We suggest performing a PFA-100 or a platelet aggregation study, when platelet dysfunction is suspected.

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Rab38 Expression in Platelet Dense Granule Storage Pool Disease.

Blood ◽

10.1182/blood.v110.11.2112.2112 ◽

2007 ◽

Vol 110 (11) ◽

pp. 2112-2112

Author(s):

Ivana Ninkovic ◽

James G. White ◽

Kenyatta W. Stephens ◽

Artur Rangel-Fihlo ◽

Francsisca C. Wu ◽

...

Keyword(s):

Platelet Aggregation ◽

Platelet Function ◽

Flow Cytometric Analysis ◽

Dense Granule ◽

Bleeding Disorder ◽

Coding Region ◽

Platelet Dysfunction ◽

Granule Formation ◽

Storage Pool ◽

Storage Pool Disease

Abstract Platelet dense granule storage pool disease (SPD) is a bleeding disorder characterized by a lack of normal platelet dense granule function, as evidenced by decreased platelet aggregation in response to ADP, epinephrine and collagen. Platelet SPD has been studied most extensively in humans and rodents with Hermansky-Pudlak syndrome (HPS), whose phenotype is a result of defects in granule trafficking, leading to oculocutanous albinism, lysosomal storage diseases, and platelet dysfunction. We have been characterizing the fawn-hooded hypertensive (FHH) rat, which has been previously shown to have a bleeding disorder consistent with a platelet SPD and some of the features of HPS. While the platelets in the FHH rat have normal alpha granules and lysosomes, they lack dense granules as assessed by transmission electron microscopy. Platelet flow cytometric analysis of GPIb and GPIIb indicated that the FHH platelets have normal surface expression of these adhesion proteins. The FHH rat has a mutation in the Rab38 gene at the ATG start site, which is associated with the bleeding disorder. Rab38 is part of a large family of GTPases, which are involved in granule formation and secretion. Western blotting of FHH tissues revealed that there is no expression of Rab38 protein. We have used confocal immunomicroscopy to assess Rab38 in platelet formation and function. In normal rat and human platelets, there was punctate expression of Rab38. There was no Rab38 staining detected in FHH platelets. In human megakaryocytic cell lines, Dami and HEL cells, there was punctate staining of Rab38 that was mainly in the periphery of the cells, with a variable amount of perinuclear staining. There was partial colocalization of Rab38 with serotonin and VWF, and with Lamp-3, a marker of lysosomes. The degree of colocalization varied between cells. There was no clear association of Rab38 with actin and tubulin in megakaryocytes. We also examined a cohort of patients with SPD, but not HPS, for mutations in Rab38. The entire coding region and intron-exon boundaries of the Rab38 gene were sequenced in 18 patient samples collected at Emory University for the CDC Women with Bleeding Disorders and Menorrhagia Study. Ten of the patients had platelet function defects documented by standard platelet aggregation studies, and eight had no identifiable platelet function defect. No mutations in Rab38 were detected. Whereas numerous known polymorphisms were identified and confirmed, there was no association of any of them with platelet function abnormalities. In conclusion, Rab38 is expressed in platelets and megakaryocytes and may interact with other granule proteins during megakaryocyte development. Failure to express Rab38 is associated with platelet dysfunction. Further studies are needed to determine its function in megakaryocytes and platelets, and to determine whether defects in Rab38 are a cause of platelet SPD in humans.

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The Power of a Standardized Bleeding Score in Diagnosing Pediatric Type 1 Von Willebrand Disease.

Blood ◽

10.1182/blood.v114.22.1293.1293 ◽

2009 ◽

Vol 114 (22) ◽

pp. 1293-1293

Author(s):

Paul D Marcus ◽

Kidan G Nire ◽

Linda Grooms ◽

Jennifer Klima ◽

Sarah O'Brien

Keyword(s):

Platelet Function ◽

Predictive Value ◽

Care Setting ◽

Tertiary Care ◽

Bleeding Disorder ◽

Von Willebrand Disease ◽

The Mean ◽

Bleeding Score ◽

Von Willebrand

Abstract Abstract 1293 Poster Board I-315 INTRODUCTION Type I von Willebrand disease (VWD) is the most common inherited bleeding disorder. Repetitive testing of von Willebrand factor (VWF) levels is necessary before the diagnosis can be safely ruled out, as VWF levels fluctuate in response to genetic and environmental factors. A predictive bleeding score (BS) could reveal individuals that may benefit from repetitive testing and those for whom repetitive testing is unlikely to be of benefit. While a standardized questionnaire (the Vicenza score) was developed to evaluate hemorrhagic symptoms, it was never prospectively validated for a pediatric population in a tertiary care setting. SUBJECTS The study targeted children, ages 0 to 17 years, referred to the Hemostasis and Thrombosis Center (HTC) of Nationwide Children's Hospital for a coagulation evaluation as a result of bleeding symptoms, family history of a bleeding disorder and/or abnormal coagulation labs found during pre-operative screening. Children were excluded if they had a previously diagnosed bleeding disorder, if their caregiver did not speak English or if the child did not undergo VWF:Ag and VWF:RCo testing. METHODS Prior to the diagnosis or exclusion of a bleeding disorder in the child, caregivers consented to answer the questionnaire over the telephone. Descriptions of the Vicenza score are available online (http://www.euvwd.group.shef.ac.uk/bleed_score.htm). LABORATORY TESTING A single VWF:Ag or VWF:RCo <30 IU/dL was classified as “Definite Type 1 VWD” while levels from 30-50 IU/dL were classified as “Low VWF” (http://www.nhlbi.nih.gov/guidelines/vwd). Platelet function analysis (PFA-100) screened for platelet function defects, with some patients undergoing follow-up platelet aggregation studies and/or platelet electron microscopy. Laboratory studies from other institutions were excluded from analysis. Patients' medical records were reviewed after hematologic evaluation, and the resultant data was analyzed with STATA 10.1 (Stata Corp., College Station, TX). RESULTS A total of 104 children (52 females and 52 males) with a mean age of 7.53 years (range 1 month to 17 years) were included. At least one hemorrhagic symptom was present in 99 of the 104 children (95%) with the mean number of symptoms being 2.87 (range 0 to 7). The mean Vicenza score was 3.24 (range -1 to 13). Of the 104 children, 8 met criteria for “Definite Type 1 VWD,” 23 met criteria for “Low VWF,” 14 were diagnosed with a “Platelet Function Defect,” and 2 children had bleeding secondary to Ehlers Danlos syndrome. Children with non-bleeding disorders (e.g. Factor XII deficiency) or no laboratory evidence of a bleeding disorder were classified as “No Bleeding Disorder.” In general, the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and positive diagnostic likelihood ratio of the bleeding questionnaire demonstrated poor predictive value in our patient population with the exception of high specificity in ruling out “Definite Type 1 VWD” (Table). The NPV was comparably high with both qualitative (>2 bleeding symptoms) and quantitative (BS ≥2) criteria. CONCLUSIONS The Vicenza score, previously validated in adults and in a pediatric primary care setting, appears to have limited predictive value in a pediatric tertiary care setting when evaluating patients with platelet function defects or low VWF levels. While the Vicenza score has a high NPV to exclude “Definite Type 1 VWD,” the use of simpler qualitative criteria is similarly predictive. Disclosures No relevant conflicts of interest to declare.

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Identification of Qualitative Platelet Disorders in Adolescent Women with Heavy Menstrual Bleeding

Blood ◽

10.1182/blood.v128.22.4922.4922 ◽

2016 ◽

Vol 128 (22) ◽

pp. 4922-4922

Author(s):

Kristina M. Haley ◽

Susan Lattimore ◽

Cara McDavitt ◽

Ayesha Khader ◽

Colin Boehnlein ◽

...

Keyword(s):

Platelet Aggregation ◽

Board Of Directors ◽

Platelet Function ◽

Research Funding ◽

Blood Platelet ◽

Bleeding Disorder ◽

Advisory Committees ◽

Adolescent Women ◽

Platelet Disorder ◽

Platelet Function Assays

Abstract Introduction: Nearly 40% of adolescent women experience heavy menstrual bleeding (HMB), and identifiable bleeding disorders are diagnosed in only 20-60% of these patients. We suspect that qualitative platelet disorders contribute to HMB, but are under-diagnosed. A pilot study was conducted to evaluate platelet function in adolescent women with HMB employing four novel, small-volume, whole blood platelet function assays. In addition, primary and secondary hemostasis, bleeding phenotype, and quality of life were assessed. Methods: Patients referred to the Young Women's Hematology Clinic at Oregon Health & Science University for evaluation of HMB were offered participation in the study. Participants underwent standard review of their medical and family history and physical exam. Standard lab evaluation included CBC, PT, PTT, fibrinogen, thrombin time, Von Willebrand Panel, PFA-100, and iron studies with platelet aggregation or phenotyping performed if clinically indicated. Using less than 0.5 mL of whole blood, platelet function was assessed with four novel platelet function assays: assessment of platelet activation, secretion, and aggregation was assessed by flow cytometry analysis, while platelet adhesion and aggregation was assessed under shear in a capillary tube. Quality of life (QOL) was assessed using the PedsQL tool. Bleeding phenotype was assessed with the ISTH Bleeding Assessment Tool (ISTH BAT). Menorrhagia was assessed with the Pictorial Bleeding Assessment Chart (PBAC), the Philipp Tool and the clinical history. Results: Nine participants have enrolled on study to date, with 2 completing the 3-month visit. The median age of the cohort was 16 years (14-18 years). Eight out of nine categorized their period as heavy, 6 also had epistaxis, and 7 reported excessive bruising. The median ISTH BAT score was 4 (3-7). Of the 7 patients who had a Philipp Score obtained, 5 were positive. Median PBAC score was 161 (64-196). Median ferritin was 13 ng/mL (4-65 ng/mL). Median QOL psychosocial score was 70 (68.36-88.25), comparable to that of pediatric patients with cancer. Of the 9 participants, 6 had platelet aggregation and phenotyping. Four participants did not receive a bleeding disorder diagnosis, 1 was diagnosed with Type 1 VWD, 1 was diagnosed with bleeding disorder, NOS, and 1 was diagnosed with Ehlers Danlos Syndrome. Two participants were diagnosed with a qualitative platelet disorder (QPD): one based on platelet aggregation and one based on thromboelastography. The four novel platelet function assays confirmed platelet function abnormalities in the participants diagnosed with QPD's (Figure 1&2). Impaired platelet response to agonist stimulation was also observed in participants with non-platelet disorder bleeding disorder diagnoses and in participants without a bleeding disorder diagnosis. Conclusions: In this pilot study, the etiology of HMB in adolescent women was evaluated with four novel platelet assays in addition to standard assays of hemostasis. A bleeding disorder diagnosis was not made with standard evaluations in 4 out of 9 participants. The novel assays detected platelet abnormalities not observed using currently available clinical labs, and confirmed the presence of abnormal platelet function in participants with abnormal platelet function testing. These assays require significantly less blood volume than currently available assays and expand investigation of platelet function to platelet adhesion and platelet interactions in whole and flowing blood. Further work is needed to determine the sensitivity and specificity of the novel assays in detecting platelet dysfunction. Continued investigation into the impact of HMB on the adolescent female population is needed. Disclosures Haley: CSL Behring: Honoraria; Baxalta: Membership on an entity's Board of Directors or advisory committees. Recht:Biogen: Membership on an entity's Board of Directors or advisory committees; CSL Behring: Membership on an entity's Board of Directors or advisory committees; Biogen: Research Funding; Genentech: Research Funding; Novo Nordisk: Research Funding; Baxalta: Research Funding; Novo Nordisk: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees.

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Abnormal Ristocetin-Aggregation of Platelets in Uraemia and on Haemodialysis Therapy

10.1055/s-0038-1665834 ◽

1979 ◽

Author(s):

H. F. Woods ◽

J. Turney ◽

M. J. Weston

Keyword(s):

Platelet Aggregation ◽

Factor Viii ◽

Bleeding Time ◽

Dialysis Patients ◽

Normal Platelet ◽

Crossover Studies ◽

Coagulant Activity ◽

Aggregation Of Platelets ◽

Ristocetin Cofactor ◽

Membrane Defect

Impaired platelet aggregation to ADP and collagen is recognised in uraemia and the loss of normal platelet function contributes to the prolonged capillary bleeding time observed in uraemia. in von Willebrand’s disease prolongation of capillary bleeding time is associated with impaired platelet aggregation to ristocetin because of a relative or absolute deficiency of the Factor VIII-Ristocetin Cofactor. We have studied platelet aggregation to ristocetin and Factor VIII coagulant activity (CA) and related antigen (RA) in 14 uraemic and 28 dialysed patients. Ristocetin aggregation (delta-0.D/min) was significantly less in uraemia (50 ± 21: m ± S.D) and in dialysis patients (38 ± 18) than in controls (78 ± 20). Factor VIII CA and RA were significantly higher in uraemic and dialysed patients than in controls.In crossover studies plasma from uraemic patients either enhanced or did not change ristocetin aggregation of normal platelets but plasma from dialysed patients impaired ristocetin aggregation of normal platelets. Plasma from dialysed patients was not contaminated by heparin. Thus in uraemia impaired platelet aggregation to ristocetin is unlikely to be due to a Factor VIII deficiency and may be due to a membrane defect as in Bernard-Soulier disease. in dialysed patients’ plasma there appears to be an additional circulating inhibitor of platelet-ristocetin interaction.

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First Report of Transheterozygosity in a Patient with An Inherited Platelet Bleeding Disorder Due to Mutations in the Thromboxane A2 Receptor (TBXA2R) and cyclooxygenase1 (PTGS1),

Blood ◽

10.1182/blood.v118.21.3260.3260 ◽

2011 ◽

Vol 118 (21) ◽

pp. 3260-3260

Author(s):

Kathleen Freson ◽

Chantal Thys ◽

Christel Van Geet

Keyword(s):

Platelet Aggregation ◽

Autosomal Recessive ◽

Conflicts Of Interest ◽

Autosomal Recessive Disorder ◽

Bleeding Disorder ◽

Bleeding Complications ◽

Normal Platelet ◽

First Case ◽

Functional Defect ◽

Sequencing Platforms

Abstract Abstract 3260 Platelet aggregation by thromboxane (TBXA2) stimulation of its G protein-coupled receptor TXA2R is initiated after conversion of arachidonic acid (AA) into prostaglandin H2 (PGH2) by cyclooxygenase1 (PTGS1) and subsequently by conversion of PGH2 into TXA2 by thromboxane synthase (TBXAS1). Hirata et al (JCI, 1994) reported the first TBXA2R mutation that resulted in reduced platelet responses to U46619 and low AA concentrations in subjects with a heterozygous R60L mutation. This functional defect in combination with mild clinical bleeding problems was only described for the one patient that was homozygous for this mutation. A second TBXA2 patient with an obvious bleeding diathesis carried a heterozygous D304N mutation but it was reported that this variant by itself could not explain the bleeding phenotype as other family members heterozygous for D304N presented with abnormal aggregation responses but no bleeding problems (Mumford, Blood, 2010). Functional SNPs in PTGS1 were described in pharmacogenetic studies including the L237M variant with 50% reduced COX1 metabolic activity but its effect on platelet function was not studied (Lee CR, Pharmacogenet Genomics, 2007). We here describe a 6-year old patient with ecchymosis, easy bruising and important post-traumatic bleeding complications after adenotonsillectomy and circumcision. The boy presents with normal coagulation parameters, normal platelet count and MPV, structurally normal platelets, normal ATP secretion by collagen, and the PFA100 closure time was normal for Col/Epi and mildly prolonged for Col/ADP. Platelet aggregation studies further showed an absent response to 1 mM AA as determined on different occasions, a reduced but not absent response to U46619 and a normal activation with ADP, ristocetin and Horm collagen. His parents and sister presented with increased sensitivity for ecchymoses but none had severe clinical bleeding problems and their platelets showed normal aggregation responses except for the father and sister with a reduced though not absent response to AA. Thromboxane B2 formation was determined and found to be normal in basal (plasma) and maximal stimulated (serum) conditions. In contrast, TXB2 levels were decreased after activation with U46619 for the patient but also for the father and sister compared to the control or mother. Activation with AA also resulted in reduced TXB2 levels for the patient and mildly reduced levels for all other family member compared to controls. This strongly suggests the presence of an autosomal recessive disorder. The TBXAS1, PTGS1 and TBXA2R genes were sequenced for the patient and we identified two heterozygous mutations in separate genes being R60H in TXBA2R and the functional L237M variant in PTGS1. Interestingly, his mother carried the L237M variant while R60H was present in father and sister with similar functional platelet defects as earlier described for the other heterogenous TBXA2R mutations but no clinical bleeding symptoms. To our knowledge, this is the first case of transheterozygosity for mutations explaining an autosomal recessive bleeding disorder. We hypothesize that this pattern of inheritance might be more common than expected and therefore this possibility should be taken into account when analyzing patients in the future using exome or genome wide sequencing platforms. Disclosures: No relevant conflicts of interest to declare.

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Abnormal Ristocetin-Aggregation of Platelets in Uraemia and on Haemodialysis Therapy

10.1055/s-0039-1684562 ◽

1979 ◽

Author(s):

H.F. Woods ◽

J. Turney ◽

M.J. Weston

Keyword(s):

Platelet Aggregation ◽

Factor Viii ◽

Bleeding Time ◽

Dialysis Patients ◽

Normal Platelet ◽

Crossover Studies ◽

Coagulant Activity ◽

Aggregation Of Platelets ◽

Ristocetin Cofactor ◽

Membrane Defect

Impaired platelet aggregation to ADP and collagen is recognised in uraemia and the loss of normal platelet function contributes to the prolonged capillary bleeding time observed in uraemia. In von Willebrand’s disease prolongation of capillary bleeding time is associated with impaired platelet aggregation to ristocetin because of a relative or absolute deficiency of the Factor VIII-Ristocetin Cofactor. We have studied platelet aggregation to ristocetin and Factor VIII coagulant activity (CA) and related antigen (RA) in 14 uraemic and 28 dialysed patients. Ristocetin aggregation (delta-0.D/min) was significantly less in uraemia (50 ± 21: m ± S.D) and in dialysis patients (38 ± 18) than in controls (78 + 20). Factor VIII CA and RA were significantly higher in uraemic and dialysed patients than in controls.In crossover studies plasma from uraemic patients either enhanced or did not change ristocetin aggregation of normal platelets but plasma from dialysed patients impaired ristocetin aggregation of normal platelets. Plasma from dialysed patients was not contaminated by heparin. Thus in uraemia impaired platelet aggregation to ristocetin is unlikely to be due to a Factor VIII deficiency and may be due to a membrane defect as in Bernard-Soulier disease. In dialysed patients’ plasma there appears to be an additional circulating inhibitor of platelet-ristocetin interaction.

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Platelet Function Disorders in Bleeding Patients without Other Coagulopathies

Blood ◽

10.1182/blood.v126.23.4650.4650 ◽

2015 ◽

Vol 126 (23) ◽

pp. 4650-4650

Author(s):

Francine R. Dembitzer ◽

Ellinor I.B. Peerschke ◽

Caroline Cromwell ◽

Xiaofei Zhang ◽

Louis M. Aledort

Keyword(s):

Platelet Aggregation ◽

Board Of Directors ◽

Platelet Function ◽

Coagulation Factor ◽

Clinical History ◽

Study Cohort ◽

Advisory Committees ◽

Normal Platelet ◽

Platelet Function Disorders ◽

Age Range

Abstract Introduction: We present a series of 105 patients referred for hematologic consultation to evaluate a clinical bleeding disorder. Little is known regarding the prevalence of non-genetic qualitative platelet disorders and which of these might respond to desmopressin. Methods: Patients were assessed over a two-year period, from December 2011 through December 2013. Patients, who were found to have neither von Willebrand's disease nor coagulation factor deficiencies, nor quantitative platelet defects, were tested for platelet function abnormalities by PFA-100 (Dade Behring, Marburg, Germany) and platelet aggregation and secretion studies using lumi aggregation (Chrono-Log Corp., Havertown, PA, USA). Selected patients with abnormal platelet function were given a trial of intravenous desmopressin to determine efficacy, and platelet function studies were repeated 2 hours later. Results: Of the 105 referred patients (26 males, age range 15-83 years; 79 females, age range 21-86 years), 67 with either normal (n=43) or abnormal (n=24) PFA-100 results were not evaluated further based on their clinical history and presentation. 18 patients with abnormal PFA-100 results, consisting of Collagen/ADP, Collagen/Epinephrine, or both, had platelet aggregation and secretion studies performed. 16 of these patients had abnormal platelet aggregation and secretion studies, while 2 patients had normal studies. In addition, 20 patients with normal PFA-100 results underwent platelet aggregation and secretion studies. Of these, 17 had abnormal platelet aggregation and secretion predominantly in response to two or more weak agonists, including ADP, epinephrine and/or arachidonic acid. Only 3 of these 20 patients had normal platelet aggregation and secretion. Of the 16 patients with both abnormal PFA-100 and abnormal platelet aggregation and secretion tests, 11 underwent subsequent pre- and post- desmopressin platelet function testing. 7 of the 11 patients showed improvement or complete normalization of at least one PFA-100 parameter, i.e., either Collagen/ADP, Collagen/Epinephrine, or both. However, results of platelet aggregation and secretion tests remained unchanged, irrespective of PFA-100 results. Conclusions: In the present study, platelet aggregation and secretion studies in patients with no other coagulopathies revealed platelet function defects in approximately 30% of the study cohort. Platelet function defects were in response to weak agonists, including ADP, epinephrine, and/or arachidonic acid.Our data support the recent SCC ISTH recommendations against the use of PFA-100 for platelet function screening.We recommend that the hematologist carefully assess the bleeding history, and, if significant, pursue platelet aggregation and secretion studies to identify potential platelet function defects. Disclosures Aledort: Baxter Healthcare: Membership on an entity's Board of Directors or advisory committees, Other: DSMB Participation; Kedrion BioPharma: Consultancy, Membership on an entity's Board of Directors or advisory committees.

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