Platelet Function Defects Research Articles

Preoperative screening for bleeding disorders: A comprehensive laboratory assessment of clinical practice

Unlabelled Box BackgroundPatients with mild bleeding disorders are at risk of perioperative bleeding, but screening for these disorders remains challenging. ObjectivesWe aimed to assess the prevalence of hemostatic abnormalities in patients with and without reported bleeding symptoms on a preoperative questionnaire, consisting of guideline‐proposed questions, and appraised the diagnostic value of several screening modalities for the identification of patients with hemostatic abnormalities. MethodsIn this observational study, 240 patients with and 95 patients without bleeding symptoms on the preoperative questionnaire were included. Patients with known bleeding disorders, antithrombotic drugs, thrombocytopenia, and anemia were excluded. Preoperatively, all patients underwent elaborate hemostatic testing. Hemostatic abnormalities were defined as coagulation, vWF, or fibrinolysis factor levels below reference range and platelet function defects. Screening modalities included the ISTH Bleeding Assessment Tool (ISTH‐BAT), PT, aPTT, TT, Euglobulin Lysis Time (ELT), and Platelet Function Analyser (PFA). ResultsIn 21 of 240 (8.8%) patients reporting bleeding symptoms, hemostatic abnormalities were found, including 7 reduced coagulation factor levels, 10 platelet function abnormalities, and 4 reduced vWF levels. In comparison, 10 of 95 (10.5%) patients not reporting bleeding symptoms had abnormalities. The ISTH‐BAT could not identify patients with abnormalities, while PT, aPTT, TT, ELT, and PFA had high specificity but low sensitivity to detect abnormalities. ConclusionsThe prevalence of hemostatic abnormalities in both patients with and without reported bleeding symptoms was 9%‐10%. This suggests that the guideline‐based questionnaire cannot differentiate between patients with and without abnormalities, while the discriminative power of the screening modalities is also limited.

Platelet transfusion: Current challenges

Since the late sixties, platelet concentrates are transfused to patients presenting with severe thrombocytopenia, platelet function defects, injuries, or undergoing surgery, to prevent the risk of bleeding or to treat actual hemorrhage. Current practices differ according to the country or even in different hospitals and teams. Although crucial advances have been made during the last decades, questions and debates still arise about the right doses to transfuse, the use of prophylactic or therapeutic strategies, the nature and quality of PC, the storage conditions, the monitoring of transfusion efficacy and the microbiological and immunological safety of platelet transfusion. Finally, new challenges are emerging with potential new platelet products, including cold stored or in vitro produced platelets. The most debated of these points are reviewed.

THE USE OF PFA-100 IN PEDIATRICS IN THE INVESTIGATION OF HEMOSTATIC DISORDERS, A RETROSPECTIVE COHORT STUDY

Abstract BACKGROUND The screening of hemostatic disorders in paediatrics is challenging because often children have never undergone hemostatic challenges. The PFA-100 was introduced as an alternative to the in vivo bleeding time test and is now routinely used in the screening of these disorders. Numerous studies have assessed its limits and there remains uncertainty regarding its utility. OBJECTIVES The goal of our study was to describe the utilization of the PFA-100 in a tertiary paediatric center, to evaluate its accuracy and to determine the average cost generated by the investigation following an abnormal result. DESIGN/METHODS We did a retrospective descriptive study by reviewing the charts of 250 paediatric patients who had a PFA-100 done in our center over a one year period. Accuracy and reliability of the PFA-100 were calculated with a ROC curve (95% CI). RESULTS Of 225 patients included in our study, 99 (44%) PFA-100’s were done in a preoperative context, and in average, each patient had 1.52 PFA-100’s (range 1–6). Personal hemorrhagic diathesis was not described in 59 patients (26.2%). 91 patients (40.4%) had an abnormal PFA-100 result. Further investigation revealed no disorder in 55 patients (60.4%), von Willebrand disease in 20 patients (8.9%) and non-specific platelet function defects in 15 patients (6.7%). No severe platelet function defects were found in our study cohort. There was a high variability of the PFA-100 result in a same patient (coefficient of variation 15.8%). A higher cut-off value of 140 seconds for PFA-100 col_EPI (AUC 0,87) and 111 seconds for PFA-100 col_ADP (AUC 0,68) produced more accurate sensitivity (89% and 74%), specificity (78% and 63%) and positive (44% and 49%) and negative (97% and 84%) predictive values, compared to our center’s threshold of 130 seconds and 100 seconds respectively. The average cost per patient for the investigation following an abnormal PFA-100 was 434,92$ ± 232,66 (CI 95%). CONCLUSION PFA-100 was mainly used in a preoperative context in our study and patient history was often incomplete. The PFA-100 shows high sensitivity and negative predictive value making it a potentially good screening test however it is to be used with caution considering the high variability of results in a single patient.

Validation of flow cytometric analysis of platelet function in patients with a suspected platelet function defect

Background Light transmission aggregometry (LTA) is the most commonly used test for the diagnosis of platelet function disorders (PFDs), but has moderate sensitivity for mild PFDs. Flow cytometry has been recommended for additional diagnostics of PFDs but is not yet standardized as a diagnostic test. We developed a standardized protocol for flow cytometric analysis of platelet function that measures fibrinogen binding and P-selectin expression as platelet activation markers in response to agonist stimulation. Objectives To determine the additional value of flow cytometric platelet function testing to standard LTA screening in a cross-sectional cohort of patients with a suspected PFD. Methods Platelet function was assessed with flow cytometry and LTA in 107 patients suspected of a PFD in whom von Willebrand disease and coagulation factor deficiencies were excluded. Both tests were compared in terms of agreement and discriminative ability for diagnosing patients with PFDs. Results Out of 107 patients, 51 patients had an elevated bleeding score; 62.7% of the patients had abnormal platelet function measured with flow cytometry and 54.2% of the patients were abnormal based on LTA. There was fair agreement between LTA and flow cytometry (κ = 0.32). The discriminative ability of flow cytometric analysis in patients with an elevated bleeding score was good (AUC 0.82, 0.74-0.90), but moderate for LTA (AUC 0.70, 0.60-0.80). Both tests combined had a better discriminative ability (AUC 0.87, 0.80-0.94). Conclusion Flow cytometric analysis of platelet function has added value in diagnostics of PFDs in patients with unexplained bleeding tendency.

High proportion of patients with bleeding of unknown cause in persons with a mild-to-moderate bleeding tendency: Results from the Vienna Bleeding Biobank (VIBB).

Data on clinical characteristics and the prevalence of underlying coagulopathies in patients with mild-to-moderate bleeding disorders (MBDs) are scarce. We established the Vienna Bleeding Biobank (VIBB) to characterize and thoroughly investigate Austrian patients with MBDs. Four hundred eighteen patients (female=345, 82.5%) were included. A platelet function defect (PFD) was diagnosed in 26 (6.2%) and a possible PFD in 30 (7.2%) patients. Eight patients (1.9%) were diagnosed with von Willebrand disease (VWD) (type 1 n=6; type 2 n=2), and 29 patients had low VWF (30-50IU/dL). Deficiencies in factor VIII, IX, XI or XIII were found in 11 (2.6%), 3 (0.7%), 3 (0.7%) and 1 patient(s), 2 patients had dysfibrinogenaemia, and further 2 had possible PFD and FXI deficiency. Probable causal mutations were detected in 8 of 11 patients with FVIII deficiency, 2 of 3 patients with FIX deficiency and 2 of 8 patients with VWD. Three hundred three patients (72.5%) had normal results in the coagulation assays and were categorized as patients with bleeding of unknown cause (BUC). The bleeding score did not differ between patients with and without established diagnosis. A diagnosis of a bleeding disorder was more frequently made in men than in women (49.3% vs 22.9%). Male sex (OR 3.55, 95% CI: 2.02-6.22; P<.001) and blood group 0 (OR 1.86, 95% CI: 1.17-2.94; P=.008) were independently associated with diagnosis of a bleeding disorder. The high rate of patients with BUC despite in-depth haemostatic assessment underlines the incompleteness of available routine laboratory tests. Males with MBDs were more likely to be diagnosed with an established bleeding disorder than females.

Thrombocytopenia in childhood: a practical guide for investigation

Abstract Platelets play a central role in haemostasis. A significant reduction in the platelet count, thrombocytopenia, and the investigation of a child prone to bleeding and bruising, are common reasons for referral to paediatric haematology physicians. This article offers a practical guide to investigation of the thrombocytopenic child. The varied aetiology of thrombocytopenia in childhood, including both acquired and congenital forms are summarised. Conditions characterised by defective platelet function are also discussed. Key themes include a focus on distinguishing the cause of thrombocytopenia from history and examination with an explanation of the tests used to confirm diagnoses in specialist centres.

Introducing high-throughput sequencing into mainstream genetic diagnosis practice in inherited platelet disorders.

Inherited platelet disorders are a heterogeneous group of rare diseases, caused by inherited defects in platelet production and/or function. Their genetic diagnosis would benefit clinical care, prognosis and preventative treatments. Until recently, this diagnosis has usually been performed via Sanger sequencing of a limited number of candidate genes. High-throughput sequencing is revolutionizing the genetic diagnosis of diseases, including bleeding disorders. We have designed a novel high-throughput sequencing platform to investigate the unknown molecular pathology in a cohort of 82 patients with inherited platelet disorders. Thirty-four (41.5%) patients presented with a phenotype strongly indicative of a particular type of platelet disorder. The other patients had clinical bleeding indicative of platelet dysfunction, but with no identifiable features. The high-throughput sequencing test enabled a molecular diagnosis in 70% of these patients. This sensitivity increased to 90% among patients suspected of having a defined platelet disorder. We found 57 different candidate variants in 28 genes, of which 70% had not previously been described. Following consensus guidelines, we qualified 68.4% and 26.3% of the candidate variants as being pathogenic and likely pathogenic, respectively. In addition to establishing definitive diagnoses of well-known inherited platelet disorders, high-throughput sequencing also identified rarer disorders such as sitosterolemia, filamin and actinin deficiencies, and G protein-coupled receptor defects. This included disease-causing variants in DIAPH1 (n=2) and RASGRP2 (n=3). Our study reinforces the feasibility of introducing high-throughput sequencing technology into the mainstream laboratory for the genetic diagnostic practice in inherited platelet disorders.

A new proposition for the screening of platelet function defects using an hematology analyzer

In this paper we suggest a new method for the screening of congenital thrombopathies using an hematology analyzer. This method is an improvement of the platelet count ratio principle which uses an impedance counter to search a decrease of the free platelet count after adding platelet agonist to whole blood. We suggest using novel platelet parameters provided by an optical hematology analyzer such as ADVIA 2120i (Siemens Healthcare Diagnostics) to search morphological and structural changes of platelet that are supposed reflecting platelet activation in normal platelets after addition of an agonist.

Developmental Stage-Specific Manifestations of Absent TPO/c-MPL Signalling in Newborn Mice.

Congenital amegakaryocytic thrombocytopaenia (CAMT) is a disorder caused by c-MPL mutations that impair thrombopoietin (TPO) signalling, resulting in a near absence of megakaryocytes (MKs). While this phenotype is consistent in adults, neonates with CAMT can present with severe thrombocytopaenia despite normal MK numbers. To investigate this, we characterized MKs and platelets in newborn c-MPL –/– mice. Liver MKs in c-MPL –/– neonates were reduced in number and size compared with wild-type (WT) age-matched MKs, and exhibited ultrastructural abnormalities not found in adult c-MPL –/– MKs. Platelet counts were lower in c-MPL –/– compared with WT mice at birth and did not increase over the first 2 weeks of life. In vivo biotinylation revealed a significant reduction in the platelet half-life of c-MPL –/– newborn mice (P2) compared with age-matched WT pups, which was not associated with ultrastructural abnormalities. Genetic deletion of the pro-apoptotic Bak did not rescue the severely reduced platelet half-life of c-MPL –/– newborn mice, suggesting that it was due to factors other than platelets entering apoptosis early. Indeed, adult GFP+ (green fluorescent protein transgenic) platelets transfused into thrombocytopenic c-MPL –/– P2 pups also had a shortened lifespan, indicating the importance of cell-extrinsic factors. In addition, neonatal platelets from WT and c-MPL –/– mice exhibited reduced P-selectin surface expression following stimulation compared with adult platelets of either genotype, and platelets from c-MPL –/– neonates exhibited reduced glycoprotein IIb/IIIa (GPIIb/IIIa) activation in response to thrombin compared with age-matched WT platelets. Taken together, our findings indicate that c-MPL deficiency is associated with abnormal maturation of neonatal MKs and developmental stage-specific defects in platelet function.

Platelet Function Prior to Ibrutinib Treatment Is More Severely Impaired in Chronic Lymphocytic Leukemia Than in Mantle Cell Lymphoma

INTRODUCTION. Ibrutinib is an oral small-molecule drug that irreversibly inhibits Bruton's tyrosine kinase and thus suppresses proliferation of B cells. Ibrutinib therapy in chronic lymphocytic leukemia (CLL) and in mantle cell lymphoma (MCL) is associated with frequent bleeding complications that were reported to be more severe in CLL. This difference was suggested to be related to differential adenosine diphosphate (ADP) disruption by CD39, expressed by tumor cells. Here we investigate platelet functional activity in CLL and MCL patients before initiation of ibrutinib.MATERIALS. Fifty one adult patients with relapsed and refractory CLL and MCL and 20 healthy donors were included in the study. Platelet functional activity was characterized by flow cytometry before and after activation with SFLLRN plus collagen-related peptide. Levels of CD42b, CD61, CD62P, PAC1, annexin V binding, and mepacrine release were determined. Aggregation with collagen, ADP and ristocetin were measured.RESULTS. Among 36 CLL patients 25 (69%) were men, the median age was 66 (range, 31 to 83 years) and 23 (64%) had a refractory disease. In 34 previously treated patients the median number of prior treatments was 2 (range, 1 - 6). Two CLL patients with del (17p) received ibrutinib as a first line. In a group of MCL patients (n=15) there were 12 men (80%), the median age was 63 years (range, 49-79). Seven (54%) patients had a high MIPI score. The median number of previous chemotherapy lines in MCL patients was 1 (range, 1 - 6). Lymphocyte count before initiation of ibrutinib was significantly higher in CLL group (median 17,5 х 109/L range 0,48 - 189,7) compared to MCL group (median 1,75 х 109/L, range 0,35 - 6,59, p=0,037). Initial platelets count was also different being lower in CLL than in MCL patients (127 х 109/L (15 - 248) versus 186 х 109/L (63 - 311), p=0,005). Platelets of untreated patients with CLL had statistically significant impairments in their responses compared to those with MCL. Specifically, they had decreased integrin activation in response to stimulation (46±19% versus 73±18%; for healthy donors, 100±17%), and relative mepacrine release (2.9±0.9 versus 3.5±0.8; healthy, 4.0±0.7). P-selectin release was impaired milder (77±17% versus 92±14%; healthy, 100±10%), and procogulant platelet formation impairment was not statistically significant (8±6% versus 12±7%; healthy, 12±3%). In control experiments, addition of MeS-AMP and MRS2179, selective inhibitors of ADP receptors, had comparable effects on the healthy donor platelets. Aggregation in response to ADP was dramatically impaired in CLL compared with MCL (24±18% versus 42±16%), as well as that in response to collagen (47±23% versus 72±13%). Upon ibrutinib treatment, further decrease of PAC1 binding and procoagulant platelets formation almost to the level of resting platelets were observed; activation with SFLLRN alone produced a similar result with donor platelets.CONCLUSIONS. Patients with CLL and MCL have initially impaired response of platelets. The defects of platelet function in CLL is much greater suggesting a possible explanation of the different clinical severity. DisclosuresVorobyev:Janssen: Speakers Bureau. Ptushkin:Janssen: Speakers Bureau.

PCTP (Phosphatidylcholine Transfer Protein) is Regulated By RUNX1 in Platelets/Megakaryocytes and is Associated with Adverse Cardiovascular Events

Transcription factor (TF) mutations are increasingly recognized to play a major role in inherited platelet abnormalities. RUNX1, a major hematopoietic TF, acts in a combinatorial manner with other TFs to regulate numerous megakaryocyte (MK)/platelet genes. Human RUNX1 haplodeficiency is associated with thrombocytopenia, platelet function defects, and increased leukemia risk. We have described a patient with multiple abnormalities in platelet aggregation and secretion responses with a heterozygous RUNX1 nonsense mutation (Sun et al Blood 2004; 103; 948-54). Transcript expression profiling of patient platelets (Sun et al J Thromb Haemost 2007; 5:146-54)showed several genes were significantly downregulated, including myosin light chain (MYL9), platelet factor 4 (PF4), protein kinase C-θ (PRCKQ), and 12-lipoxygenase (ALOX12); these have been shown by us to be regulated by RUNX1. The profiling data also showed 10-fold downregulation of phosphatidylcholine transfer protein (PCTP) gene (fold change ratio 0.09, p=0.02) in the patient compared with normal controls. PCTP regulates the intermembrane transfer of phosphatidylcholine (PC), a major plasma membrane phospholipid. Platelet PCTP expression is associated with increased platelet aggregation and calcium mobilization upon activation of protease-activated receptor 4 (PAR4) thrombin receptors in black subjects as compared to white subjects (Edelstein et al Nat Med 2013; 19:1609-16). Pharmacologic inhibition of PCTP decreased platelet aggregation in response to PAR4 agonist and siRNA knockdown of PCTP in megakaryocytic cells blunted calcium mobilization induced by PAR4 (Edelstein et al Nat Med 2013; 19:1609-16). Little is known regarding the regulation of PCTP in MKs/platelets and its role in cardiovascular events.Based on the decreased platelet PCTP expression in our patient, we pursued the hypothesis that PCTP is regulated by RUNX1 and contributes to cardiovascular events. Corrected total cellular immunofluorescence with anti-PCTP antibody showed significantly reduced platelet PCTP expression by 58% in our patient compared to a normal control. In silico analysis revealed 5 RUNX1 consensus binding sites up to ~ 1 kb of the PCTP 5’ upstream region from ATG. To assess for interaction of RUNX1 with the PCTP promoter, chromatin immunoprecipitation (ChIP) assay with anti-RUNX1 antibody was performed using human erythroid leukemia (HEL) cells treated with phorbol 12-myristate 13-acetate (PMA) for 48 hours to induce megakaryocytic transformation. The ChIP studies showed RUNX1 binding to PCTP chromatin in the regions encompassing RUNX1 binding site 1 (-345/-340), site 3 (-632/-627), and encompassing sites 4 and 5 (-974/-969, -997/-992). Electrophoretic mobility shift assay (EMSA) using PMA-treated HEL cell nuclear extracts showed RUNX1 binding to DNA probes (28-37 bp) containing site 1 (-345/-340) and both sites 4 and 5 (-974/-969, -997/-992). PCTP mRNA and protein expression were increased with RUNX1 overexpression and reduced with RUNX1 knockdown in HEL cells, indicating that PCTP is regulated by RUNX1. To assess the clinical relevance of the findings, the relationship between RUNX1 and PCTP in peripheral blood RNA, and PCTP and death or myocardial infarction (MI) events were assessed in two separate patient cohorts (n = 587 total patients) with cardiovascular disease. RUNX1 is transcribed from two alternate promoters (P1 and P2) resulting in different isoforms. In both patient cohorts, there was strong correlation between RUNX1 and PCTP expression in a promoter specific manner. RUNX1 P1 probe sets were strongly and inversely correlated with PCTP expression (p < 0.0001), while the P2 probe sets were not. PCTP expression was associated with death or MI in both patient cohorts (odds ratio 2.1, 95% CI [1.61-2.95], P-value < 0.0001) independent of age, sex, race, platelet count, and cardiovascular risk factors.Conclusions: Our results provide evidence that PCTP is regulated by RUNX1 (potentially in a promoter specific manner), and that PCTP expression is associated with death or myocardial infarction in patients with cardiovascular disease. RUNX1 regulation of PCTP may play a role in the pathogenesis of platelet-mediated cardiovascular events. DisclosuresNo relevant conflicts of interest to declare.

Chronic Pancytopenia and Increased Bone Density Due to TBXAS1 Deficiency

Non-dysmorphic 32-year old Caucasian female developed malaise, fluctuating body aches and progressive transfusion-dependent pancytopenia with peripheral blood morphology consistent with myelodysplastic syndrome (MDS). Reportedly, she had an episode of "low blood counts" of unclear etiology 23 years prior. Multiple attempts at bone marrow biopsy were unsuccessful due to technical difficulties with penetrating the bone, necessitating surgical biopsy by an orthopedic surgeon. Bone densitometry revealed increased bone density with Z-score of 4.5, consistent with mild thickening of long bone diaphysis noted via x-ray. Strikingly, the bone marrow biopsy revealed haphazard ossification, immature cartilage formation and thickened trabeculae replacing hematopoiesis within the marrow cavity. Next-generation sequencing revealed two novel biallelic mutations within the thromboxane synthase gene TBXAS1 (c.266T>C; c.989T>C). Both mutations affected conserved amino acid residues and were predicted to be disruptive to the protein function by two independent bioinformatics algorithms (Provean and PolyPhen-2).Thromboxane cascade regulates pathways of inflammation, coagulation and osteoclast activation, suggesting a mechanistic explanation of how thromboxane synthase malfunction causes abnormal bone remodeling and bone marrow failure. TBXAS1 disruption had been described in a rare autosomal recessive syndrome Ghosal hematodiaphyseal dysplasia (GHDD) associated with increased bone density and bone marrow failure. GHDD due to TBXAS1 mutations was genetically confirmed only in four families of Northern African and Middle Eastern descent (Nat Genet 2008; 40: 284-286). To our knowledge, this is the first genetically validated case of TBXAS1-/- Ghosal syndrome in the Caucasian population.Consistent with the well-established role of thromboxane in platelet function, our patient's platelets displayed impaired aggregation in response to arachidonic acid and structural abnormalities by transmission electron microscopy, revealing a functional platelet defect. Steroid therapy rendered the patient transfusion-independent and alleviated chronic pain and inflammation. A long-term follow-up will be needed to determine whether steroid treatment will result in stable improvement in hematopoiesis and decreased bone density, similar to other GHDD patients. This case illustrates how establishing the diagnosis of an underlying rare inherited bone marrow failure syndrome allows personalized, evidence-based treatment with lower risk of morbidity compared to cytotoxic chemotherapy and hematopoietic stem cell transplantation. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Research Progress of Platelet Transfusion in China.

Platelet products have been increasingly used for more than 50 years. Platelet transfusion is effective for correcting bleeding caused by thrombocytopenia and platelet function defects. In this review, we will outline research on platelet transfusion in China including platelet biosafety, cryopreservation of platelets, the assessment of the effectiveness of platelet transfusion, the causes of platelet transfusion refractoriness including immunization against CD36, and neonatal alloimmune thrombocytopenia.

All too common: bleeding and genetic variation

Inherited bleeding disorders are both common and challenging to diagnose, particularly when the disorder is mild (reviewed in references [1, 2]). Most mild bleeding disorder patients are not routinely bleeding in their daily lives, and it can be difficult to differentiate bleeding events common in healthy populations from events which rise to the level of pathology. Fundamental to the diagnosis of bleeding disorders is a detailed assessment of the history of the patient and the family. This article is protected by copyright. All rights reserved.

Iron Overload and Platelet Function Defects: Possible Correlation.

Acquired platelet function defect might be a consequence of iron overload. Even though there are various complications of iron overload, only few reports have indicated some correlations with platelets dysfunction. We report a child with Diamond-Blackfan anemia who has significant complications from iron overload due to chronic blood transfusion, and one of these complications is acquired platelet function defect that manifests with frequent episodes of epistaxis. Therefore, we emphasize the necessity for further studies to confirm direct correlation between iron overload as a causative agent and platelets dysfunction. And we recommend screening for platelets function in patients receiving chronic blood transfusion aiming at possible prevention of any life-threatening bleeding.

The utility of International Society on Thrombosis and Haemostasis-Bleeding Assessment Tool and other bleeding questionnaires in assessing the bleeding phenotype in two platelet function defects.

The main objective of this study is to investigate the utility of International Society on Thrombosis and Haemostasis-Bleeding Assessment Tool (ISTH-BAT) in comparison with the condensed form of Molecular and Clinical Markers for the Diagnosis and Management of type 1 and WHO BATs, in assessing bleeding in two well known and clinically significant platelet function defects. Thirty-eight patients previously diagnosed with Glanzmann's thrombasthenia and 10 with Bernard-Soulier syndrome (BSS) were analyzed. Bleeding scores were significantly higher than that of controls using both electronic bleeding questionnaire (eBQ) and ISTH-BAT with no significant difference between both tools. ISTH-BAT had a sensitivity, specificity, positive predictive value and negative predictive value of 100%, 76.2%, 0.9 and 1. This was closely similar to eBQ. Both ISTH-BAT and eBQ are efficient in BSS and Glanzmann's thrombasthenia. However, given the ISTH recommendation, ISTH-BAT should be adopted. Larger study including other platelet defects will enhance its utility and support the integration of bleeding scores with standardized laboratory testing to allow for a universal diagnostic approach to patients with suspected bleeding disorders.

Perioperative Coagulopathy and the Clinical Implications

Perioperative bleeding as conceived in this review refers to the clinical scenario whereby there is impairment of blood coagulation leading to prolonged or excessive bleeding, accompanying trauma or surgical exposure. Aetiology of bleeding disorders could be classified under the following subheadings: vascular disorders, Thrombocytopenia, Platelet function defects, Coagulation factors disorder(s). Primary haemostasis is initiated or triggered by the release of tissue factor at the site of injury leading to generation of small quantity thrombin, sufficient to activate platelets leading to the formation of prothrombin complex. The ability of FXa to activate FVII creates a link between the extrinsic and intrinsic coagulation pathways; leading to the generation of sufficient thrombin to convert fibrinogen to fibrin which organizes platelet plug to indissoluble clots (Secondary haemostasis) or thrombus formation. A balance is required between haemostasis, thrombosis and fibrinolysis to prevent perioperative coagulopathy. Whenever positive findings in the history and physical examination suggests an increased risk of significant bleeding, then it is more cost effective to carry out routine screening tests of coagulation. Specific coagulation tests used routinely has longer turnaround times and is not appropriate in the perioperative setting. Current recommendations for the prevention of massive bleeding in the perioperative setting; requires communication of appropriate treatment plans in a multidisciplinary setting, intraoperative monitoring, the treatment of underlying disorder, and replacement therapy with blood products. As point-of-care diagnostics becomes available in emergency areas, timely targeted intervention for haemorrhage control will result in better patient outcomes and reduced demand for blood products.

CEACAM2 positively regulates integrin αIIbβ3-mediated platelet functions

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is an Ig-ITIM superfamily member that regulates integrin αIIbβ3 function. We hypothesized that its twin protein, CEACAM2, exerts a similar physiologic role in murine platelets. CEACAM2-deficient mice (Cc2−/−) displayed prolonged tail bleeding times and increased volume of blood loss. Cc2−/− platelets have moderate integrin αIIbβ3-mediated functional defects with impaired kinetics of platelet spreading on fibrinogen and type I collagen and delayed kinetics in the retraction of fibrin clots in vitro. This functional integrin αIIbβ3 defect could not be attributed to altered integrin αIIbβ3 expression. Cc2−/− platelets displayed normal ‘inside-out’ signaling properties as demonstrated by normal agonist-induced binding of soluble fluorescein isothiocyanate (FITC)-fibrinogen and JON/A antibody binding. This data provides direct evidence that disruption of CEACAM2 induces a moderate integrin αIIbβ3-mediated platelet function defect, and that CEACAM2 is essential to maintain a normal integrin αIIbβ3-mediated platelet function.

Current and emerging approaches for evaluating platelet disorders.

Platelets play a central role in physiological hemostasis and also in pathological thrombosis. It is well established that congenital or acquired abnormalities of platelet function are associated with a heightened risk of bleeding of variable severity and excessive hemorrhage after surgery or trauma. Several kinds of different platelet function tests have been developed over the years to identify or diagnose platelet function disorders. The use of these tests for the assessment of thrombotic risk or for monitoring the effects of drugs inhibiting platelet function is not well established. Light transmission aggregometry (LTA) is the gold standard for the study of patients with defects of platelet function. Its results are affected by several pre-analytical and analytical variables. The Subcommittee on Platelet Physiology of the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis published official guidelines for the standardization of the variables affecting LTA, which should be followed to harmonize the procedures across different laboratories worldwide. The lumi-aggregometer, a modification of LTA that measures platelet secretion in parallel with aggregation, is preferable to LTA for diagnosing inherited defects of platelet function, because it is more sensitive to the most common disorders, which are characterized by abnormalities of platelet secretion. LTA (or lumi-aggregometry) is useful as a first screening test of patients with the clinical suspicion of defects of platelet function, because it helps to provide an interim diagnostic hypothesis, which can then be confirmed or discounted using appropriate and specific tests.

Haematological spectrum and genotype-phenotype correlations in nine unrelated families with RUNX1 mutations from the French network on inherited platelet disorders.

BackgroundLess than 50 patients with FPD/AML (OMIM 601309) have been reported as of today and there may an underestimation. The purpose of this study was to describe the natural history, the haematological features and the genotype-phenotype correlations of this entity in order to, first, screen it better and earlier, before leukaemia occurrence and secondly to optimize appropriate monitoring and treatment, in particular when familial stem cell transplantation is considered.MethodsWe have investigated 41 carriers of RUNX1 alteration belonging to nine unrelated French families with FPD/AML and two syndromic patients, registered in the French network on rare platelet disorders from 2005 to 2015.ResultsFive missense, one non-sense, three frameshift mutations and two large deletions involving several genes including RUNX1 were evidenced. The history of familial leukaemia was suggestive of FPD/AML in seven pedigrees, whereas an autosomal dominant pattern of lifelong thrombocytopenia was the clinical presentation of two. Additional syndromic features characterized two large sporadic deletions. Bleeding tendency was mild and thrombocytopenia moderate (>50 x109/L), with normal platelet volume. A functional platelet defect consistent with a δ-granule release defect was found in ten patients regardless of the type of RUNX1 alteration. The incidence of haematological malignancies was higher when the mutated RUNX1 allele was likely to cause a dominant negative effect (19/34) in comparison with loss of function alleles (3/9). A normal platelet count does not rule out the diagnosis of FPD/AML, since the platelet count was found normal for three mutated subjects, a feature that has a direct impact in the search for a related donor in case of allogeneic haematopoietic stem cell transplantation.ConclusionsPlatelet dysfunction suggestive of defective δ-granule release could be of values for the diagnosis of FPD/AML particularly when the clinical presentation is an autosomal dominant thrombocytopenia with normal platelet size in the absence of familial malignancies. The genotype-phenotype correlations might be helpful in genetic counselling and appropriate optimal therapeutic management.