Venous thromboembolism and hypercoagulability in splenectomized patients with thalassaemia intermedia

An update on recent studies of extracellular vesicles and their role in hypercoagulability in thalassemia (Review)

Thromboembolic events are a significant clinical concern in thalassemia and hemoglobinopathies, highlighting the need for new strategies to treat and detect these specific hematologic complications. In recent years, extracellular vesicles (EVs) have garnered interest due to their role in cell-to-cell communication, including angiogenesis, immune responses and coagulation activation. Their multifaceted role depends on the cellular origin and cargo, making them potential diagnostic biomarkers and therapeutic agents. The present review highlights recent advances in understanding the involvement of EVs in hypercoagulability in thalassemia, the characterization of circulating EVs and the potential for using EVs as predictive biomarkers. β-Thalassemia intermedia exhibits a high incidence of thromboembolic events, contributing to significant morbidity and mortality. Advanced technologies have enabled the profiling and characterization of circulating EVs in patients with β-thalassemia through various techniques, including flow cytometry, proteomic studies, reverse transcription-quantitative PCR, transmission electron microscopy, nanoparticle tracking analysis and western blot analysis. Microparticles from splenectomized β-thalassemia/hemoglobin E patients induce platelet activation and aggregation, potentially contributing to thrombus formation. The abundance of these microparticles, primarily released from platelets and damaged red cells, may have a role in thromboembolic events and other clinical complications in thalassemia. This suggests a promising future for EVs as diagnostic and predictive biomarkers in thalassemia management.

Splenectomy is significantly associated with thrombosis but not with pulmonary hypertension in patients with transfusion-dependent thalassemia: a meta-analysis of observational studies

Introduction

Thromboembolism (TE) and pulmonary hypertension (PH) constitute frequently occurring complications in patients with transfusion-dependent thalassemia and have been associated with splenectomy in different studies. Nevertheless, the size of the possible association varies greatly in literature. Herein, we sought to provide pooled effect estimates regarding the impact of splenectomy on TE and PH in transfusion dependent thalassemia (TDT) by retrieving relevant, available studies.

Methods

We systematically searched articles published in PubMed, Cochrane library, Scopus and gray literature from inception until the 30th of May, 2023. Pooled estimates in terms of odds ratios (OR) and 95% confidence intervals (CI) were calculated according to outcome measures. Risk of bias and quality of studies were evaluated.

Results

Regarding TE, 4 studies were selected for meta-analysis and the pooled data demonstrated that splenectomy was significantly associated with this outcome in TDT patients [OR = 4.08, 95% CI (1.03, 16.11), p = 0.04]. On the other hand, we pooled data from seven investigating PH, and, interestingly, the quantitative analysis revealed no association between splenectomy and PH [OR = 1.76, 95% CI (0.91, 3.41), p = 0.1].

Conclusion

Splenectomy is associated with higher risks of TE, but not with PH in patients with TDT.

Preoperative anemia and deep vein thrombosis in patients with perioperative bone trauma: a cohort study

Background

In current active prevention (including physical and drug prevention), the incidence of perioperative deep vein thrombosis (DVT) of the lower extremities remains high in patients with bone trauma. Risk factors need to be further optimized, and high-risk patients must be identified early. Preoperative comorbidities, especially preoperative anemia, and DVT in patients with perioperative bone trauma are not clear. The purpose of this study was to explore the causal relationship between preoperative anemia and DVT in patients with perioperative bone trauma, and further reduce the incidence of DVT in patients with bone trauma.

Objectives

To analyze the relationship between preoperative anemia and perioperative DVT in patients with femoral and pelvic fractures and provide a reference for the optimization of risk factors for DVT.

Methods

The clinical data of 1049 patients with femoral and pelvic fractures who received surgical treatment from May 2018 to June 2021 were retrospectively analyzed. Propensity score matching (PSM) was performed for the covariates of DVT. Modified Poisson regression was used to analyze the relationship between preoperative anemia and DVT.

Results

After matching 1:1 propensity scores in 1049 patients included in this study, there were 258 patients in the anemic and non-anemic groups. Preoperative anemia was statistically significant for the formation of DVT in patients with perioperative bone trauma (P = 0.000, RR = 1.567 [95% CI 1.217–2.017]). This conclusion remained true after PSM (P = 0.009, RR = 1.500 [95% CI 1.105–2.036]). Preoperative anemia has some predictive value for perioperative DVT, with DVT-associated preoperative anemia thresholds of 125 g/L and area under the receiver operating characteristic curve of 0.5877 (95% CI 0.5345 to 0.6408). On this basis, sensitivity and specificity were 89.2 and 30.3%, respectively, with a Youden index of 0.195. In addition, we conducted an E-value determination of the propensity score; the E-value analysis showed robustness to unmeasured confounding.

Conclusions

Preoperative anemia is highly correlated with perioperative DVT in patients with bone trauma, which is the cause of perioperative DVT in these patients.

Clinical and genetic characteristics of hemoglobin H disease in Iran

Hemoglobin H (Hb H) disease is a subtype of α-thalassemia caused by deletional and/or non-deletional mutations in three alpha-globin genes in which the various genotypes determine the disease severity. This study was aimed to investigate the frequency of alpha gene mutations and genotypes and their correlation with hematological and clinical characteristics in Iran. Among 202 patients diagnosed with Hb H disease through a national study in Iran according to standard methods, we had access to the hematologic and clinical findings and genetic data of 101 patients in whom genetic study was performed. Genomic DNA from peripheral blood was extracted and analyzed for identification of α-globin gene mutations using Multiplex Gap Polymerase Chain Reaction, Reverse Hybridization Assay, and finally Direct DNA Sequencing method. Twenty-one different mutations and thirty genotypes were detected in 101 patients with Hb H disease. In total, 39 patients (38.6%) were deletional and 62 patients (61.4%) were non-deletional type of the disease. The _--^MED mutation was highly prevalent in almost half of the patients (56.4%). Among various genotypes, -^MED/-a^3.7 (29.7%) and -α^20.5/-α^5NT (6.9%) were the most prevalent genotypes found in the studied group. Patients with non-deletional type presented with more severe hematological and clinical findings. Hb H percentage and serum ferritin levels were significantly higher in non-deletional patients in comparison to the deletional group (p < 0.05). 12 (11.9%) and 40 (39.6%) out of 101 patients were on regular and occasional transfusions, respectively. 83% of those with regular transfusion belonged to the non-deletional group. Among transfusion-dependent patients, -^MED/α^CSα and α^20.5/-α^5NT were the most common genotypes. In this study, two patients with -α^20.5/α^CSα and -^MED/α^-5NT genotypes experienced thrombotic events. This study indicated that although non-deletional genotypes of Hb H disease were responsible for more clinical severity of the disease, due to the presence of severe phenotypes even in deletional types, no definite correlation was found between genotype and phenotype.

Bleeding Versus Thrombotic Tendency in Young Children With Beta-Thalassemia Major

Introduction

Bleeding and thrombotic events are known to occur in beta-thalassemia major (BTM) patients and have been attributed to hepatic iron overload associated with multiple blood transfusions. We evaluated hemostatic parameters in children with BTM who had no previous history of bleeding or thrombotic episodes.

Materials and Methods

Hemostatic parameters including prothrombin time (PT), activated partial thromboplastin time (APTT), platelet aggregation, protein C and S, iron profile, and liver function tests were evaluated in 54 children (median age = 12 months, age range = 4-144 months) with BTM and 15 age and sex-matched controls.

Results

The mean PT and APTT of patients were significantly higher (P=0.016 and P <.001) than that of controls. Mean protein C, protein S activity and platelet aggregability with adenosine 5-diphosphate (ADP) as an agonist in patients were significantly lower (P <.001, P <.001 and P=0.007, respectively) than that in controls. Mean serum ferritin in BTM children was not significantly elevated to be associated with hepatic dysfunction.

Conclusion

Deranged hemostatic parameters indicative of bleeding and thrombotic tendencies are observed in BTM children from an early age and may not be solely due to hyperferritinemia-associated hepatic dysfunction. Despite the presence of deranged hemostatic parameters, a state of balance exists between bleeding and thrombosis, and an imbalance may lead to bleeding or thrombotic events at a later age.

The Association Between Parameters of Erythrocytes Morphology and Thrombophilia-Related Mutations

BACKGROUND

Alterations in erythrocyte morphology parameters have been identified and associated with hematological disorders and other chronic and cardiovascular diseases. Erythrocytes are abundant in thrombus content. Their hemoglobin density and differences in the ratio of macrocytic and microcytic cells may be associated with hypercoagulopathy in those with a history of thrombosis.

OBJECTIVE

This cross-sectional study aimed to investigate the relationship between hemogram parameters and thrombophilia genetic parameters.

METHOD

A total of 55 patients whose thrombophilia panel was reviewed due to the diagnosis of thrombosis were included in the study. %MIC, %MAC, %HPO, %HPR and all hemogram parameters were measured using Abbott Alinity HQ. Prothrombin G20210A, MTHFR C677T, MTHFR A1298C, Factor V Leiden G169A and PAI-1 4G/5G mutations were studied using Real Time-PCR.

RESULTS

The MTHFR C677T mutation was detected in 58.2% of the patients. The Factor V Leiden mutation was detected in 5.5% of the patients. The MTHFR A1298C mutation was detected in 58.2%, The PAI mutation was detected in 74.5%, and the Factor 13 mutation was detected in 29% of the patients. Prothrombin G20210A mutation was not detected in any of the patients. Red blood cell (RBC) and Hct values were higher in Factor 13 mutant group; the Hgb and Htc values were higher in the MTHFR C677T mutant group.

CONCLUSION

The MTHFR C677T and Factor 13 mutations may be associated with high Hct and RBC, Hgb, and Htc values, respectively and coagulation tendency in patients with a history of thrombosis.

Pitfalls in the Diagnosis of β-Thalassemia Intermedia

We present case histories of three patients who had β-thalassemia (β-thal) trait with 'unusual severity' managed as β-thal intermedia (β-TI) where the basis of disease severity could not be explained with routine hematological and genetic investigations. The clinical diagnosis of 'thalassemia intermedia' was justifiable as they had a β-thal mutation and disease severity that did not fit in with either β-thal trait or with β-thal major (β-TM). As mutations of α, β, and γ genes could not explain the unusual severity of the disease, further analysis with next-generation sequencing (NGS) for red cell diseases was carried out, which led to the diagnosis of coexisting membranopathies. This case series highlights the inherent difficulty in the diagnosis of β-TI with certainty in some patients where the genetic basis is not clear-cut.

Disease Knowledge and General Self-Efficacy Among Adolescents with Thalassemia Major and Their Parents' Perspective

Thalassemia major can affect physical, psycho-social and economic life of patients and their parents. The aim of the study was to assess the disease knowledge and general self-efficacy among adolescents with Thalassemia major and their parents' perspective with a view to develop an informational booklet on thalassemia. In a cross-sectional study 50 adolescents along with 48 parents were recruited from the hematology day care centre of a tertiary care facility. Ethical clearance from institute ethics committee, written informed consent from parent and assent from the adolescent were taken. Consecutive participants those who consented were enrolled in the study. Adolescents between the age group of 10-18 years, and their parents completed the self-developed subject data sheet, knowledge questionnaire and standardized general self-efficacy tools. The mean knowledge scores of the adolescent and their parents related to thalassemia were 13.9 ± 2.9 and 13.7 ± 3.6 respectively, while the perceived GSE scores of the adolescent along with the parents' perspective were 30.1 ± 6.1 and 29.3 ± 6.5. Positive correlation between the adolescents' knowledge with GSE (r = 0.464, p = 0.007) was observed. The knowledge of the adolescents and their parents showed significant association with the education (p = 0.001, p = 0.002) residence (p = 0.04 and p = 0.01) and parents' employment (p = 0.04). The knowledge of adolescents with thalassemia and their parents is limited. There is need to counsel the adolescents and their parents about the disease and its management in order to improve the GSE of these adolescents.

Surface area-to-volume ratio, not cellular viscoelasticity, is the major determinant of red blood cell traversal through small channels

The remarkable deformability of red blood cells (RBCs) depends on the viscoelasticity of the plasma membrane and cell contents and the surface area to volume (SA:V) ratio; however, it remains unclear which of these factors is the key determinant for passage through small capillaries. We used a microfluidic device to examine the traversal of normal, stiffened, swollen, parasitised and immature RBCs. We show that dramatic stiffening of RBCs had no measurable effect on their ability to traverse small channels. By contrast, a moderate decrease in the SA:V ratio had a marked effect on the equivalent cylinder diameter that is traversable by RBCs of similar cellular viscoelasticity. We developed a finite element model that provides a coherent rationale for the experimental observations, based on the nonlinear mechanical behaviour of the RBC membrane skeleton. We conclude that the SA:V ratio should be given more prominence in studies of RBC pathologies.

MTHFR C677T, Prothrombin G20210A, and Factor V Leiden (G1691A) Polymorphism and Beta-Thalassemia Risk: A Meta-Analysis

Background Beta (β)-thalassemia major patients frequently suffer from many vascular problems. Thrombophilia is a blood disorder that comprises imbalances in the blood coagulating factor due to ecological and hereditary components. Previous evidence shows that thrombosis is the commonest risk in beta-thalassemia patients. Several studies have examined that MTHFR C677T, prothrombin G20210A (PT G20210A), and Factor V Leiden G1691A (FVL G1691A) polymorphism play a crucial role in the development of β-thalassemia major, yet the result was questionable and uncertain. Therefore, in this study, we executed the correlation between these gene polymorphisms with β-thalassemia major patients. Methods Suitable keywords were used to search related articles in PubMed, Google Scholar, and Web of Science. In this random-effects meta-analysis, we analyzed the odds ratio (OR) for the estimation of risk. Results A total of nine research articles with 645 β-thalassemia major patients and 989 healthy controls were incorporated in this meta-analysis. The pooled OR was assessed in MTHFR C677T, PT G20210A, and FVL G1691A polymorphism. This random-effects meta-analysis demonstrated that MTHFR C677T, PT G20210A, and FVL G1691A gene polymorphism did not significantly associate with β-thalassemia major. Moreover, the heterogeneity was significantly found in genotype CC vs CT+TT C677T (I²=61%) and allele C vs T (I²=71%) of MTHFR and genotype GG vs GA (I²=95%), GG vs GA+AA (I²=95%), GA vs GG+AA (I²=95%), and allele G vs A (I²=93%) of FVL G1691A. Conclusion The results of this meta-analysis show that MTHFR C677T, prothrombin G20210A, and Factor V Leiden (G1691A) gene polymorphism are not a risk factor for β-thalassemia major.

Recommendations for Pregnancy in Rare Inherited Anemias

Rare inherited anemias are a subset of anemias caused by a genetic defect along one of the several stages of erythropoiesis or in different cellular components that affect red blood cell integrity, and thus its lifespan. Due to their low prevalence, several complications on growth and development, and multi-organ system damage are not yet well defined. Moreover, during the last decade there has been a lack of proper understanding of the impact of rare anemias on maternal and fetal outcomes. In addition, there are no clear-cut guidelines outlining the pathophysiological trends and management options unique to this special population. Here, we present on behalf of the European Hematology Association, evidence- and consensus-based guidelines, established by an international group of experts in different fields, including hematologists, gynecologists, general practitioners, medical geneticists, and experts in rare inherited anemias from various European countries for standardized and appropriate choice of therapeutic interventions for the management of pregnancy in rare inherited anemias, including Diamond-Blackfan Anemia, Congenital Dyserythropoietic Anemias, Thalassemia, Sickle Cell Disease, Enzyme deficiency and Red cell membrane disorders.

Intravascular hemolysis triggers ADP-mediated generation of platelet-rich thrombi in precapillary pulmonary arterioles

Patients with hereditary or acquired hemolytic anemias have a high risk of developing in situ thrombosis of the pulmonary vasculature. While pulmonary thrombosis is a major morbidity associated with hemolytic disorders, the etiological mechanism underlying hemolysis-induced pulmonary thrombosis remains largely unknown. Here, we use intravital lung microscopy in mice to assess the pathogenesis of pulmonary thrombosis following deionized water-induced acute intravascular hemolysis. Acute hemolysis triggered the development of αIIbβ3-dependent platelet-rich thrombi in precapillary pulmonary arterioles, which led to the transient impairment of pulmonary blood flow. The hemolysis-induced pulmonary thrombosis was phenocopied with intravascular ADP- but not thrombin-triggered pulmonary thrombosis. Consistent with a mechanism involving ADP release from hemolyzing erythrocytes, the inhibition of platelet P2Y12 purinergic receptor signaling attenuated pulmonary thrombosis and rescued blood flow in the pulmonary arterioles of mice following intravascular hemolysis. These findings are the first in vivo studies to our knowledge to suggest that acute intravascular hemolysis promotes ADP-dependent platelet activation, leading to thrombosis in the precapillary pulmonary arterioles, and that thrombin generation most likely does not play a significant role in the pathogenesis of acute hemolysis-triggered pulmonary thrombosis.

Evaluating viscoelastic properties and membrane electrical charges of red blood cells with optical tweezers and cationic quantum dots - applications to β-thalassemia intermedia hemoglobinopathy

Biomechanical and electrical properties are important to the performance and survival of red blood cells (RBCs) in the microcirculation. This study proposed and explored methodologies based on optical tweezers and cationic quantum dots (QDs) as biophotonic tools to characterize, in a complementary way, viscoelastic properties and membrane electrical charges of RBCs. The methodologies were applied to normal (HbA) and β-thalassemia intermedia (Hbβ) RBCs. The β-thalassemia intermedia disease is a hereditary hemoglobinopathy characterized by a reduction (or absence) of β-globin chains, which leads to α-globin chains precipitation. The apparent elasticity (μ) and membrane viscosity (η_m) of RBCs captured by optical tweezers were obtained in just a single experiment. Besides, the membrane electrical charges were evaluated by flow cytometry, exploring electrostatic interactions between cationic QDs, stabilized with cysteamine, with the negatively charged RBC surfaces. Results showed that Hbβ RBCs are less elastic, have a higher η_m, and presented a reduction in membrane electrical charges, when compared to HbA RBCs. Moreover, the methodologies based on optical tweezers and QDs, here proposed, showed to be capable of providing a deeper and integrated comprehension on RBC rheological and electrical changes, resulting from diverse biological conditions, such as the β-thalassemia intermedia hemoglobinopathy.

Low levels of coagulation inhibitors: A high-risk thrombotic factor in thalassemic patients

BACKGROUND AND AIM

The β-thalassemia major (β-TM) is defined as a hereditary red blood cell-related disease. Thrombotic events are associated with thalassemia in adult patients. Thus, the present investigation was aimed to examine some hemostatic parameters, including anti thrombin-III (AT-III), protein-C (PRC) and protein-S (PRS) in β-TM patients.

METHODS

Thirty B-TM patients who referred for routine follow-up admission to the thalassemia clinic of Kerman Special Disease Center alongside with 30 healthy subjects were selected and enrolled in the present study. Further registration, the peripheral blood specimens were collected after 3 weeks of last transfusion and then the plasma concentrations of AT-III, PRC and PRS were measured in them.

RESULTS

We have observed that the concentrations of natural coagulation inhibitors (PRC and PRS) were significantly attenuated in β-TM patients (P<0.05), while the plasma level of AT-III was not remarkably differed in β-TM patients in compare to healthy subjects.

CONCLUSION

According to the findings of present work, significant changes in the PRC, PRS and AT-III which could be observed in multi transfused β-TM patients may attribute as critical risk factors for the development of upcoming thromboembolic events in their future life.

Splenectomy is not associated with a higher tricuspid regurgitant jet velocity in people with sickle cell anemia

BACKGROUND

Vascular complications such as pulmonary hypertension (PH) occur at an increased rate following splenectomy in patients with various hemolytic blood disorders including thalassemia. The goal of this retrospective cross-sectional analysis was to assess the independent association of splenectomy with an elevated tricuspid regurgitation velocity (TRV) in people with homozygous sickle cell disease (HbSS). TRV is a noninvasive screening test for PH and a surrogate marker of prognosis in sickle cell disease (SCD).

PROCEDURE

Data were obtained from the multicenter Walk-PHaSST (treatment of pulmonary hypertension and sickle cell disease with sildenafil therapy) study of PH (NCT00492531). We compared TRV in the cohort of patients with HbSS who were surgically splenectomized with patients who were not surgically splenectomized.

RESULTS

We found no significant differences in TRV between the two groups.

CONCLUSIONS

The lack of difference in TRV between the two groups is most likely because members of the comparator nonsurgical group in many cases experienced autoinfarction of the spleen in childhood. Splenectomy does not seem to confer additional risk for the development of a higher TRV in HbSS, unlike in patients with thalassemia or other hemolytic anemias. This could be an important consideration when weighing the risks and benefits of splenectomy in patients with HbSS.

Thalassemia and Moyamoya syndrome: unfurling an intriguing association

INTRODUCTION

Moyamoya angiopathy (MMA) is a rare cerebrovascular disease with progressive bilateral narrowing of intracranial parts of the internal carotid artery and proximal parts of the anterior and middle cerebral artery resulting in recurrent hemodynamic ischemic attacks, strokes and hemorrhages. If associated with other diseases, it is called Moyamoya syndrome (MMS). Until now, MMS has rarely been described with thalassemia.

METHODS

Of the 75 cases of MMA collected in our Indian center in the last 3 years, 4 new patients with the rare cooccurence of thalassemia and MMS were found. Thalassemia cases were confirmed by hemoglobin electrophoresis and MMA was diagnosed on the basis of MR angiography. Other known secondary causes of MMA were ruled out by relevant investigations. Thirteen previously reported cases of thalassemia and MMA were retrieved by literature search in PubMed and Google Scholar using the keywords "Moyamoya" AND "thalassemia". Subsequently all the data were analyzed and compared by using descriptive statistics.

RESULTS

Analysis of our 4 cases and those 13 found in the literature showed early childhood diagnosis of thalassemia and in most cases later manifestation of MMS in the age of 14.5 + 10.72 years (mean + SD) in our cases and with 10.97 + 6.47 years in previous cases. While 9 out of the former 13 and 3 of our 4 cases showed obvious infarcts in brain imaging, 1 case with HbE-β-thalassemia presented with intracerebral hemorrhage. Hemiplegia/hemiparesis was present among all of our 4 cases, while it was present in 69.23% cases of the previous 13 reports. Neither transfusion dependence nor the history of splenectomy was found to be associated with MMA development.

CONCLUSION

These four new cases of MMS in thalassemia enlarged our knowledge about MMS in patients with thalassemia. MMS is a relevant complication in patients with thalassemia and early detection is essential to avoid disability.

[Hemolytic disorders and venous thrombosis: An update]

Many factors can contribute to the risk of venous thrombosis observed in hemolytic diseases. Some mechanisms are related to hemolysis by itself, while others seem more specific to each disease. Despite recent advances in the quantification of this risk and in understanding its physiopathology, the association of hemolysis with venous thrombosis is often unknown. The purpose of this general review is to clarify the main pro-thrombotic mechanisms during hemolysis and to synthesize the clinical data currently available. We will focus on the main types of hemolytic pathologies encountered in current practice, namely paroxysmal nocturnal hemoglobinuria, hemoglobinopathies, auto-immune hemolytic anemia and thrombotic microangiopathies.

The improvement of pulmonary artery pressure after bosentan therapy in patients with β-thalassemia and Doppler-defined pulmonary arterial hypertension

Introduction

Pulmonary arterial hypertension (PAH) is relatively prevalent in patients with thalassemia. PAH treatment is necessary as the prevalence of Doppler-estimated PAH and the resultant mortality is high in such patients.

Materials and methods

This study aimed at evaluating the effect of bosentan therapy on patients with thalassemia suspected of PAH. Based on pulsed Doppler echocardiography, all the cases were suspected of severe PAH. Consequently, bosentan was initiated at a dose of 62.5 mg twice a day for 4 weeks, which was increased to 62.5–125 mg twice a day, if no adverse side effects were observed.

Results

The results of this study showed that pulmonary artery pressure (PAP) decreased after the administration of bosentan in three cases, from 160 to 120, 110 to 65, and 60 to 25 mmHg; in other words, the PAP reduced in the mentioned cases by 25%, 36.4%, and 58.4%, respectively.

Conclusion

In this study, PAP improved after bosentan therapy in patients with β-thalassemia suspected of PAH; however, further studies are required to confirm the findings.

Role of platelets in thrombin generation amongst patients with non-transfusion-dependent thalassaemia

Non-transfusion-dependent thalassaemia (NTDT) is associated with a hypercoagulable state with thrombotic risk highest after splenectomy. Various mechanisms have been proposed. Although an antiplatelet agent is commonly recommended as thromboprophylaxis in NTDT, the role of platelets contributing to this hypercoagulable state is not well-defined. This study aims to evaluate the role of platelets contributing to hypercoagulability in NTDT patients using thrombin generation (TG). Platelet-rich (PRP) and platelet-poor plasma (PPP) were collected from NTDT patients (n = 30) and normal controls (n = 20) for TG measurement and compared. Controls had higher endogenous thrombin potential (ETP) in PPP (1204.97 nM.min vs 911.62 nM.min, p < 0.001) and PRP (1424.23 nM.min vs 983.99 nM.min, p < 0.001) than patients. Patients' mean normalized ETP ratio [{PRP ETP (patient)/PPP ETP (patient)}/{mean PPP ETP (controls)/mean PPP ETP (controls)}], demonstrated that the presence of platelet does not alter ETP (mean ratio 0.97, 95% CI 0.93-1.02, equivalence defined as 10%). Types of thalassaemia, splenectomy, and severity of liver iron overload did not significantly influence patients' ETP in PPP and PRP by multivariate analysis. Platelets did not increase the TG potential of NTDT patients. Instead of being hypercoagulable, our NTDT patients were hypocoagulable by ETP measurement, although this could not be conclusively demonstrated to correlate with their iron overloading state giving rise to reduced synthesis of coagulation factors. The guideline recommendations for thromboprophylaxis with antiplatelet agents in similar NTDT patients should be re-examined.

Fertility and Pregnancy in Women with Transfusion-Dependent Thalassemia

As more women with transfusion-dependent thalassemia are seeking pregnancy, ensuring the best outcomes for both the mother and baby requires concerted, collaborative efforts between practitioners and the family. Proactive counseling, early fertility evaluation, recent developments in reproductive technology, and optimal management of iron overload, have resulted in more successful pregnancies and the birth of healthy newborns. With advances in technology for prenatal screening and increased awareness to perform screening for hemoglobinopathies, healthy pregnancy outcomes have become the expectation. Topics that require further study include management that allows fertility preservation, improved non-invasive prenatal diagnosis methods for affected fetuses, the use of chelation therapy during pregnancy, and indications for and duration of anticoagulation.

Sickle cell disease, sickle trait and the risk for venous thromboembolism: a systematic review and meta-analysis

Background

Globally, sickle cell disease (SCD) is one of the most common haemoglobinopathy. Considered a public health problem, it leads to vessel occlusion, blood stasis and chronic activation of the coagulation system responsible for vaso-occlussive crises and venous thromboembolism (VTE) which may be fatal. Although contemporary observational studies suggest a relationship between SCD or sickle trait (SCT) and VTE, there is lack of a summary or meta-analysis data on this possible correlation. Hence, we propose to summarize the available evidence on the association between SCD, SCT and VTE including deep vein thrombosis (DVT) and pulmonary embolism (PE).

Methods

We searched PubMed and Scopus to identify all cross-sectional, cohort and case-control studies reporting on the association between SCD or SCT and VTE, DVT or PE in adults or children from inception to April 25, 2017. For measuring association between SCD or SCT and VTE, DVT, or PE, a meta-analysis using the random-effects method was performed to pool weighted odds ratios (OR) of risk estimates.

Results

From 313 records initially identified from bibliographic databases, 10 studies were eligible and therefore included the meta-analysis. SCD patients had significantly higher risk for VTE (pooled OR 4.4, 95%CI 2.6–7.5, p < 0.001), DVT (OR 1.1, 95% CI 1.1–1.2, p < 0.001) and PE (pooled OR 3.7, 95% CI 3.6–3.8, p < 0.001) as compared to non SCD-adults. A higher risk of VTE (OR 33.2, 95% CI 9.7–113.4, p < 0.001) and DVT (OR 30.7, 95% CI 1.6–578.2, p = 0.02) was found in pregnant or postpartum women with SCD as compared to their counterparts without SCD. Compared to adults with SCT, the risk of VTE was higher in adults with SCD (pooled OR 3.1, 95% CI 1.8–5.3, p < 0.001), and specifically in SCD pregnant or postpartum women (OR 20.3, 95% CI 4.1–102, p = 0.0003). The risk of PE was also higher in adults with SCD (OR 3.1, 95% CCI 1.7–5.9, p = 0.0004) as compared to those with SCT. The risk of VTE was higher in individuals with SCT compared to controls (pooled OR 1.7, 95% CI 1.3–2.2, p < 0.0001), but not in pregnant or postpartum women (OR 0.9, 95% CI 0.3–2.9, p = 0.863). Compared to controls, SCT was associated with a higher risk of PE (pooled OR 2.1, 95% CI 1.2–3.8, p = 0.012) but not of DVT (pooled OR 1.2, 95% CI 0.9–1.7, p = 0.157).

Conclusion

Individuals with SCD, especially pregnant or postpartum women, might have a higher risk of VTE compared to the general population. SCT might also increases the risk of VTE. However, currently available data are not sufficient to allow a definite conclusion. Further larger studies are needed to provide a definitive conclusion on the association between SCD, SCT and VTE.

Electronic supplementary material

The online version of this article (10.1186/s12959-018-0179-z) contains supplementary material, which is available to authorized users.

How I manage medical complications of β-thalassemia in adults

The complex pathophysiology in β-thalassemia can translate to multiple morbidities that affect every organ system. Improved survival due to advances in management means that patients are exposed to the harmful effects of ineffective erythropoiesis, anemia, and iron overload for a longer duration, and we started seeing new or more frequent complications in adult compared with younger patients. In this article, we highlight particular aspects of managing adult patients with β-thalassemia, using our own experience in treating such patients. We cover both transfusion-dependent and nontransfusion-dependent forms of the disease and tackle specific morbidities of highest interest.

Microparticles from β-thalassaemia/HbE patients induce endothelial cell dysfunction

Thromboembolic complication occurs frequently in β-thalassaemia/HbE patients, particularly in splenectomised patients. Endothelial cells play an important role in thrombosis. There is strong evidence of endothelial cell activation and dysfunction in β-thalassaemia. Microparticles (MPs) are associated with thrombosis and endothelial cell dysfunction in many diseases including β-thalassaemia. However, the effect of thalassaemic-MPs on endothelial cells mediating thrombus formation has not been elucidated. In this study, the effects of circulating MPs from β-thalassaemia/HbE patients on endothelial cell functions were investigated. The results showed that MPs directly induce tissue factor, interleukin (IL)-6, IL-8, intracellular adhesion molecule-1, vascular cell adhesion molecule-1 and E-selectin expression in human umbilical vein endothelial cells (HUVECs). Notably, the levels of these endothelial cell activation markers were significantly increased in HUVECs treated with MPs obtained from splenectomised β-thalassaemia/HbE patients when compared to MPs from non-splenectomised patients or normal subjects. The increased endothelial cell activation ultimately lead to increased monocyte-endothelial cell adhesion. THP-1 and HUVECs adhesion induced by MPs from normal subjects, non-splenectomised and splenectomised patients increased to 2.0 ± 0.4, 2.3 ± 0.4 and 3.8 ± 0.4 fold, respectively when compared to untreated cells. This finding suggests that MPs play an important role on thrombosis and vascular dysfunction in β-thalassaemia/HbE disease, especially in splenectomised cases.

Role of red blood cells "annexin V" and platelets "P-selectin" in patients with thalassemia

OBJECTIVE/BACKGROUND

Certain hemostatic anomalies found in patients with thalassemia suggest the existence of a chronic hypercoagulable state. Several etiologic factors may play a role in the pathogenesis of the hypercoagulable state in those patients. One of these factors is abnormal thalassemic red blood cells (RBCs), which may provide a procoagulant. To substantiate these findings, we measured the ability of RBCs from thalassemia patients to bind annexin V with increased fraction of platelets carrying the activation marker CD62P (P-selectin). To study the expression of RBC annexin V and platelets P-selectin in study patients (those with thalassemia major, thalassemia intermedia, thalassemia minor) and control group, four-color flow cytometry was performed and the correlation between these two markers was evaluated.

METHODS

A case-control study was conducted on 50 β-thalassemia patients (10 patients with thalassemia minor, 30 patients with thalassemia major, and 10 patients with thalassemia intermedia, with 10 normal adult volunteers as a control) from June 2016 to March 2017. Flow cytometry was used to study the expression of anionic phospholipids (Annexin V) on the RBCs and CD62P (P-selectin) on the activated platelet.

RESULTS

The mean expression of annexin V in patients with thalassemia major and intermedia was significantly higher than that in the control group and patients with thalassemia minor. Although the mean expression was higher in patients with thalassemia intermedia than in those with thalassemia major, it was not statistically significant.

CONCLUSION

The mean expression of platelets P-selectin in patients with thalassemia major and thalassemia intermedia was significantly higher than that in controls and patients with thalassemia minor. However, its expression was significantly higher in patients with thalassemia intermedia than in those with thalassemia major. Annexin V also showed a positive correlation with P-selectin, and both markers positively correlated with regularity of blood transfusion.

Pregnancy Complications in a-Thalassemia (Hemoglobinopathy H): A Case Study

Thalassemia intermedia (TI) is a clinical definition which represents a wide spectrum of thalassemia genotypes but mainly includes patients who do not require or only occasionally require transfusion. An uncommon case of a 32-year-old Greek woman, para 1, at the 22nd week + day 3 of gestation with thalassemia intermedia (she was splenectomized), where her pregnancy was complicated with portal vein thrombosis, splenic thrombosis, and partial HELLP, is described. This is a generally uncommon event in thalassemia intermedia. She had no transfusion as her hematologist consulted and she took anticoagulation therapy. Thus, we present for the first time in the literature a case of HbH a-thalassemia pregnant woman whose pregnancy was complicated with portal vein thrombosis, splenic vein thrombosis, and partial HELLP; she was treated with anticoagulation therapy and she had a successful outcome.

Protein C and Anti-Thrombin-III Deficiency in Children With Beta-Thalassemia

Background

Thromboembolic events (TEEs) are recently described complications in thalassemia patients. Many mechanisms were postulated for thrombosis. Conflicting results of natural anticoagulants values were reported in previous studies. Our aim was to investigate protein C and anti-thrombin-III (AT-III) levels in thalassemics and to detect risk factors for their decrement.

Methods

A cross-sectional study for 60 beta-thalassemia patients (35 major and 25 intermedia) and 35 healthy children were tested for protein C and AT-III levels, liver function tests and Sr. ferritin.

Results

A significant reduction in protein C and AT-III levels was noticed in patient group compared to healthy children (82.50% (32 - 175) vs. 104% (60 - 204), P = 0.041 and 237.52 ± 53.19 mg/L vs. 322.99 ± 56.57 mg/L, P value ≤ 0.001, respectively). Protein C was lower among older patients (> 10 years) than younger patients (< 10 years), and splenectomized category than non-splenectomized one (P = 0.02 and 0.011, respectively). AT-III was significantly lower among splenectomized patients as compared to those who did not undergo splenectomy (P = 0.04). Significant correlations were found between protein C and AT-III with older age and liver functions.

Conclusions

Protein C and AT-III were significantly lower among thalassemics with the main risk factors for their deficiencies being: splenectomy and increasing age. This allows establishment of early prophylactic policy against TEE for the vulnerable group.

The association between idiopathic thrombocytopenic purpura and cardiovascular disease: a retrospective cohort study

Essentials We estimated the cardiovascular risk of patients with idiopathic thrombocytopenic purpura (ITP). The risk of cardiovascular disease was 38% higher in ITP patients compared with controls. Among the ITP patients, splenectomy was associated with higher cardiovascular disease. Clinicians should consider cardiovascular risk when managing ITP patients.

SUMMARY

Background Idiopathic thrombocytopenic purpura (ITP) is classically characterized by a transient or persistent decrease of platelet count. Mortality is higher in the ITP population than the general population, with a possible association with increased cardiovascular disease (CVD). Objectives The objective was to assess the strength of the association between ITP and CVD, with a secondary aim to assess the impact of splenectomy on CVD. Methods A population-based retrospective, open cohort study using clinical codes was performed using data from 6591 patients with ITP and 24 275 randomly matched controls (up to 1:4 ratio matched by age, sex, body mass index and smoking status). The main outcome was the risk of CVD, which included ischemic heart disease, stroke, trans-ischemic attack and heart failure. Adjusted incidence rate ratios were calculated using Poisson regression. Results During a median 6-year observation period there was a CVD diagnosis recorded in 392 (5.9%) ITP patients and 1114 (4.5%) control patients. There was an increased risk of developing CVD in the ITP cohort (incidence rate ratio [IRR], 1.38; 95% confidence interval [CI], 1.23-1.55), which remained robust even after a sensitivity analysis only including incident cases of ITP. Findings suggested that patients who had undergone splenectomy were at even further increased risk of developing CVD when compared with the ITP population who had not undergone splenectomy (adjusted IRR, 1.69; 95% CI, 1.22-2.34). Conclusion There is an increased risk of developing CVD in patients with ITP and even further increased risk for those patients with ITP who underwent splenectomy.

β-Thalassemia intermedia: a comprehensive overview and novel approaches

β-Thalassemia intermedia is a clinical condition of intermediate gravity between β-thalassemia minor, the asymptomatic carrier, and β-thalassemia major, the transfusion-dependent severe anemia. It is characterized by a significant clinical polymorphism, which is attributable to its genetic heterogeneity. Ineffective erythropoiesis, chronic anemia, and iron overload contribute to the clinical complications of thalassemia intermedia through stepwise pathophysiological mechanisms. These complications, including splenomegaly, extramedullary erythropoiesis, iron accumulation, leg ulcers, thrombophilia, and bone abnormalities can be managed via fetal hemoglobin induction, occasional transfusions, chelation, and in some cases, stem cell transplantation. Given its clinical diversity, thalassemia intermedia patients require tailored approaches to therapy. Here we present an overview and novel approaches to the genetic basis, pathophysiological mechanisms, clinical complications, and optimal management of thalassemia intermedia.

Elevations of Thrombotic Biomarkers in Hemoglobin H Disease

BACKGROUND

Thalassemia is a group of hereditary hemoglobinopathies caused by decreased or absent synthesis of α and/or β globin chains. Studies have shown that hypercoagulability and thrombosis are common clinical symptoms in β-thalassemia, especially β-thalassemia intermedia, but little is known about in α-thalassemia. This study aims to examine phosphatidylserine (PS) levels, platelet activation, and coagulation markers in splenectomized (S) and nonsplenectomy (NS) patients with hemoglobin (Hb) H disease.

METHODS

The NS group comprised 20 patients (median age 15.0 years, range, 14-16.5 years), and the S group consisted of 11 patients (median age 16.4 years, range, 14-19.9 years) with Hb H disease; the control group consisted of 20 normal subjects. Hematological parameters were collected. Flow cytometry was used to measure PS exposure on red blood cells. The levels of intercellular adhesive molecule (ICAM)-1, tumor necrosis factor α (TNFα), β-thromboglobulin (TG) and prothrombin fragment 1 + 2 (F1.2) were determined using ELISA test kits.

RESULTS

Significant increases in the levels of PS, ICAM-1, TNFα, β-TG, and F1.2 were observed in both patient groups compared to normal controls (p < 0.01).

CONCLUSION

This observation indicates blood coagulation, endothelial injury, chronic low-grade inflammation, platelet activation, and thrombin generation are present in Hb H disease; these findings merit further assessment in a larger prospective cohort to establish possible links with thrombotic manifestations.

Non-Transfusion-Dependent Thalassemia: An Update on Complications and Management

Patients with non-transfusion-dependent thalassemia (NTDT) experience many clinical complications despite their independence from frequent transfusions. Morbidities in NTDT stem from the interaction of multiple pathophysiological factors: ineffective erythropoiesis, iron overload (IOL), and hypercoagulability. Ineffective erythropoiesis and hemolysis are associated with chronic hypoxia and a hypercoagulable state. The latter are linked to a high prevalence of thromboembolic and cerebrovascular events, as well as leg ulcers and pulmonary hypertension. IOL in NTDT patients is a cumulative process that can lead to several iron-related morbidities in the liver (liver fibrosis), kidneys, endocrine glands (endocrinopathies), and vascular system (vascular disease). This review sheds light on the pathophysiology underlying morbidities associated with NTDT and summarizes the mainstays of treatment and some of the possible future therapeutic interventions.

Review of the Association between Splenectomy and Chronic Thromboembolic Pulmonary Hypertension

Recent evidence suggests that there may be a link between splenectomy and the later development of pulmonary hypertension, in particular World Health Organization group IV pulmonary hypertension (chronic thromboembolic pulmonary hypertension). Epidemiological studies have demonstrated an odds ratio as high as 18 for the development of chronic thromboembolic pulmonary hypertension after splenectomy in comparison with matched control subjects who have not undergone splenectomy. The mechanisms governing the association between removal of the spleen and the subsequent development of chronic thromboembolic pulmonary hypertension remain incompletely understood; however, recent advances in understanding of coagulation homeostasis have shed some light on this association. Splenectomy increases the risk of venous thromboembolic disease, a necessary precursor of chronic thromboembolic pulmonary hypertension, by generating a prothrombotic state. This prothrombotic state likely results from a reduction in the removal of circulating procoagulant factors from the bloodstream after splenectomy. Although much is to be learned, circulating microparticles have emerged as the most likely mediator for the development of thrombosis after splenectomy. Apparently because of a reduction in reticuloendothelial cell clearance, microparticle levels are elevated in patients after splenectomy. Elevated circulating microparticle levels have been linked to thromboembolism and pulmonary hypertension in a dose-dependent fashion. It is important for health care providers to be aware of the link between splenectomy and chronic thromboembolic pulmonary hypertension. We are optimistic that clarification of the exact mechanisms that govern this association will yield clinical guidelines and potential treatments.

Coagulation defects in thalassemic patients

BACKGROUND

Regular blood transfusion and compliance with iron chelation therapy has markedly improved life expectancy in thalassemia; however, this improvement is accompanied by several complications of this chronic disease including thromboembolic disorders. The objective of this work is to study natural coagulation inhibition as well as the fibrinolysis processes in thalassemic children who are otherwise in a steady state with no overt clinical manifestations of thromboembolism.

METHODS

In a case-control study design conducted at Sohag University Hospital, Sohag, Egypt, 50 thalassemic children and 20 age- and sex-matched healthy controls were compared as regards prothrombin concentration, international normalized ratio, partial thromboplastin time, protein C, protein S, antithrombin III, D-dimers, and thrombin activatable fibrinolysis inhibitor (TAFI).

RESULTS

When compared to healthy controls, natural coagulation inhibitors (protein C, protein S, and antithrombin-III) were significantly lower in thalassemic children (p < 0.0001). While D-dimers showed a significant increase in thalassemic children, TAFI was significantly lower (p < 0.0001). Splenectomized thalassemic children showed significantly lower levels of protein C, protein S and TAFI (p < 0.001, p < 0.0001, p < 0.0001, respectively) when compared to nonsplenectomized thalassemic children.

CONCLUSION

Significant changes in natural coagulation inhibition and fibrinolysis processes favoring thromboembolism can be detected in otherwise healthy thalassemic children. Because these changes are more pronounced in splenectomized patients, study of primary prophylactic strategies in this subgroup is warranted.

Red blood cells in thrombosis

Red blood cells (RBCs) have historically been considered passive bystanders in thrombosis. However, clinical and epidemiological studies have associated quantitative and qualitative abnormalities in RBCs, including altered hematocrit, sickle cell disease, thalassemia, hemolytic anemias, and malaria, with both arterial and venous thrombosis. A growing body of mechanistic studies suggests that RBCs can promote thrombus formation and enhance thrombus stability. These findings suggest that RBCs may contribute to thrombosis pathophysiology and reveal potential strategies for therapeutically targeting RBCs to reduce thrombosis.

Epidemiologic study of major complications in adolescent and adult patients with thalassemia in Northeastern Thailand: the E-SAAN study phase I

INTRODUCTION

Thalassemia-related complications are one of the main factors that increase morbidity and mortality in aging patients with thalassemia. This study was aimed to report the prevalence and clinical risk factors for the complications in thalassemia.

METHODS

A multi-center prospective cohort study was conducted in patients with thalassemia aged ≥10 years old. Thalassemia-related complications were heart failure, pulmonary hypertension, extramedullary hematopoiesis, endocrine disorders, infections, thrombosis and leg ulcers. The clinical parameters significantly associated with the complications were analyzed by logistic regression methods.

RESULTS

The prevalence of thalassemia-related complications was 60.5% in patients with transfusion-dependent thalassemia (TDT) and 43% in patients with non-transfusion-dependent thalassemia (NTDT). Splenectomy was statistically associated with complications in both TDT and NTDT patients (adjusted odds ratio (AOR) = 7.4, p-value = 0.0001 and AOR = 2.6, p-value = 0.001). Age ≥50 years old (AOR = 2.9, p-value = 0.04) and female gender (AOR = 0.5, p-value = 0.03) were statistically associated with the complications in patients with NTDT.

CONCLUSION

Nearly half of the patients in this cohort had disease-related complications. Splenectomy and advanced age were important factors for complication involvement. Early screening for the complications may reduce the morbidity and mortality in patients with thalassemia.

Evaluation of safety of concomitant splenectomy in living donor liver transplantation: a retrospective study

In Asian countries, concomitant splenectomy in living donor liver transplantation (LDLT) is indicated to modulate the portal vein pressure in the small-sized graft to protect against small for size syndrome. While concomitant splenectomy in deceased donor liver transplantation is almost contraindicated based on Western Reports of increased mortality and morbidity rate due to septic complications, there are few studies about that in LDLT. So, we retrospectively investigated the clinical outcome of adult LDLT at Kyoto University Hospital from July 2010 to July 2016. We divided the patients (n = 164) into those with concomitant splenectomy (n = 88) and those without (n = 76). The splenectomy group showed significantly increased operative time and intraoperative blood loss (P = 0.008, P = 0.0007, respectively), and significantly higher rate of postoperative splenic vein thrombosis and cytomegalovirus infection (P = 0.03, P = 0.016, respectively). However, there were no significant differences between the two groups regarding the incidence of postoperative hemorrhage (P = 0.06), post-transplant bacteremia (P = 0.38), infection-related mortality rates (P = 0.8), acute rejection (P = 0.87), and patient and graft survival (P = 0.66, P = 0.67 respectively); finally, model for end-stage liver disease score above 30 was an independent predictor for infection-related mortality post-transplant (HR = 5.99, 95% CI = 2.15-16.67, P = 0.001). In conclusion, concomitant splenectomy in LDLT can be safely performed when indicated.

HbE/β-Thalassemia and Oxidative Stress: The Key to Pathophysiological Mechanisms and Novel Therapeutics

SIGNIFICANCE

Oxidative stress and generation of free radicals are fundamental in initiating pathophysiological mechanisms leading to an inflammatory cascade resulting in high rates of morbidity and death from many inherited point mutation-derived hemoglobinopathies. Hemoglobin (Hb)E is the most common point mutation worldwide. The βE-globin gene is found in greatest frequency in Southeast Asia, including Thailand, Malaysia, Indonesia, Vietnam, Cambodia, and Laos. With the wave of worldwide migration, it is entering the gene pool of diverse populations with greater consequences than expected.

CRITICAL ISSUES

While HbE by itself presents as a mild anemia and a single gene for β-thalassemia is not serious, it remains unexplained why HbE/β-thalassemia (HbE/β-thal) is a grave disease with high morbidity and mortality. Patients often exhibit defective physical development, severe chronic anemia, and often die of cardiovascular disease and severe infections. Recent Advances: This article presents an overview of HbE/β-thal disease with an emphasis on new findings pointing to pathophysiological mechanisms derived from and initiated by the dysfunctional property of HbE as a reduced nitrite reductase concomitant with excess α-chains exacerbating unstable HbE, leading to a combination of nitric oxide imbalance, oxidative stress, and proinflammatory events.

FUTURE DIRECTIONS

Additionally, we present new therapeutic strategies that are based on the emerging molecular-level understanding of the pathophysiology of this and other hemoglobinopathies. These strategies are designed to short-circuit the inflammatory cascade leading to devastating chronic morbidity and fatal consequences. Antioxid. Redox Signal. 26, 794-813.

Circulating microparticles and the risk of thromboembolic events in Egyptian beta thalassemia patients

The presence of elevated numbers of circulating microparticles (MPs) has been hypothesized to be responsible for the occurrence of thromboembolic events (TEEs) in thalassemic patients. Our aim is to evaluate the presence and the thrombotic risk of circulating MPs in thalassemia patients and to determine the difference in MPs between β-thalassemia major (β-TM) and thalassemia intermedia (TI). The percentage of the annexin-labeled MPs, platelet-derived MPs (PMPs), erythrocyte-derived MPs (RMPs), and endothelial-derived MPs (EMPs) was measured by flow cytometry, in 87 thalassemia patients (39 β-TM and 48 TI). By multiple regression analysis, we then assessed the various independent risk factors for the occurrence of TEE. The thalassemic patients who experienced TEE had a significantly higher platelet count, higher percentage of annexin-labeled MPs, and higher percentage of PMPs (p value = 0.014, 0.003, and 0.014, respectively). There was no significant difference between β-TM and TI patients at the level of any of the studied MPs. The predictive risk factors for TEE in thalassemic patients were splenectomy, total and direct bilirubin, the RMPs, and the EMPs (OR = 10.07 (CI = 3.7-27.1), 4.3 (CI = 2.1-8.7), 1.4 (CI = 1.5-6.2), 1.6 (CI = 1.1-2.2), 3.0 (CI = 1.9-4.9), respectively). In conclusion, the elevated numbers of circulating MPs is a risk factor for the TEE in thalassemia patients.

Platelet haemostatic properties in β-thalassaemia: the effect of blood transfusion

BACKGROUND

Patients with thalassaemia may have thromboembolic events and, even without thrombosis, they have a subclinical hypercoagulable state. In this setting, several coagulation laboratory abnormalities have been described, but thus far no studies have explored the contribution of platelet adhesive and procoagulant properties to blood clotting activation. In this study, we dissected the platelet procoagulant effect and influence of blood transfusions on haemostasis and platelet function in thalassaemic patients.

MATERIAL AND METHODS

Sixteen subjects with thalassaemia were studied (9 with transfusion-dependent β-thalassaemia, 7 "trait" carriers). Splenectomised and non-splenectomised patients undergoing blood transfusion were compared. All splenectomised patients were then compared to "trait" carriers and to healthy controls (n=9). The following parameters were measured in transfusion-dependent patients before and after monthly transfusions and compared to those of controls: levels of platelet surface activation markers (P-selectin, tissue factor, and fibrinogen), whole blood platelet aggregation, tissue factor or adenosine diphosphate (ADP)-induced platelet thrombin generation (TG) potential, and D-dimer.

RESULTS

Before transfusion, platelets from splenectomised patients showed significantly higher ADP-induced tissue factor expression, ADP- and collagen-induced platelet aggregation and TG potential than those from non-splenectomised patients and controls. Blood transfusion in splenectomised patients reduced platelet activation, aggregation and TG potential.

DISCUSSION

Splenectomised patients with β-thalassaemia had a prothrombotic state, characterised by enhanced platelet reactivity and function, and high platelet-induced TG potential. One hour after blood transfusions platelet and coagulation parameters improved, supporting the hypothesis that transfusion might have a protective role on platelet haemostatic status.