Coagulation activation in children with sickle cell disease is associated with cerebral small vessel vasculopathy

Determination of the Level of von Willebrand Factor, ADAMTS13, and Ratio of ADAMTS13:von Willebrand Factor in Sickle Cell Disease Patients

BACKGROUND

Sickle cell anemia (SCA) is a hypercoagulable state characterized by a significant alteration in hemostatic parameters which may predispose an increased risk of vaso-occlusive crisis (VOC). Sickle cell disease (SCD) is the most common genetic disorder in sub-Saharan Africa. Nigeria bears a high disease burden with an estimated prevalence of 1%-3% of its population being affected by the disease. The study seeks to determine the role of von Willebrand factor (VWF), ADAMTS13, and the ratio of ADAMTS13:VWF antigen in the pathogenesis of VOC.

OBJECTIVE

The objective of this study is to evaluate the level of VWF, ADAMTS13, and their ratio in SCD subjects in Calabar and to determine their role in the pathogenesis of VOC.

METHODOLOGY

This is a comparative study carried out at the University of Calabar Teaching Hospital (UCTH), Calabar. Sixty SCA patients were evaluated in VOC and steady states as well as five parented healthy controls. VWF: Ag and ADAMTS13:Ag were evaluated using Assaypro enzyme-linked immunosorbent assay kits with Lot nos. 01751728 and 04222167R, respectively. Data were analyzed by IBM SPSS Chicago software version 21. The study was approved by the UCTH Institution Ethical Review Board.

RESULTS

The mean ages of the SCA subjects and controls were 23.5 ± 7.2 years and 26.5 ± 5.6 years, respectively (P = 0.706). There were 23 (38.3%) males in the SCA group and 21 (42.0%) females in the controls. There was no significant difference in their sex distribution (P = 0.063). The mean (standard deviation [SD]) of VWF in VOC, steady state, and controls were 2.52 ± 0.34, 1.34 ± 0.23, and 1.41 ± 0.23 IU/mL, respectively. The differences in mean were significantly higher in VOC state (P = 0.003). The mean ± SD of ADAMTS13 in VOC, steady state, and controls were 0.61 ± 0.10, 0.44 ± 0.06, and 0.62 ± 0.10 μg/L, respectively. ADAMTS13 levels did not differ significantly across the groups (P = 0.270). Similarly, there was no significant difference between ADAMTS13:VWF ratios across the groups (P = 0.318).

CONCLUSION

VWF level is elevated in VOC state and thus may be implicated in the pathogenesis of VOC. ADAMTS13 and the ratio of ADAMTS13:VWF are not significantly affected in VOC.

The Highs and Lows of ADAMTS13 Activity

Severe deficiency of ADAMTS13 (<10 iu/dL) is diagnostic of thrombotic thrombocytopenic purpura (TTP) and leads to accumulation of ultra-large vWF multimers, platelet aggregation, and widespread microthrombi, which can be life-threatening. However, the clinical implications of a low ADAMTS13 activity level are not only important in an acute episode of TTP. In this article, we discuss the effects of low ADAMTS13 activity in congenital and immune-mediated TTP patients not only at presentation but once in a clinical remission. Evidence is emerging of the clinical effects of low ADAMTS13 activity in other disease areas outside of TTP, and here, we explore the wider impact of low ADAMTS13 activity on the vascular endothelium and the potential for recombinant ADAMTS13 therapy in other thrombotic disease states.

Early-onset indicators of a hypercoagulable state and clinical complications in a cohort of children with sickle cell trait

Adults with sickle cell trait (SCT) have a procoagulant state with increased risk of thromboembolism, but limited data are available for children. We compared the coagulation profile of children with SCT, different sickle cell disease (SCD) genotypes, and healthy controls. Compared to controls and similarly to HbSC patients, 41 SCT children (mean age 6.85 years; 20 males; 88% Africans) had a characteristic procoagulant profile: higher levels of factor VIII, von Willebrand factor (VWF) Ag and CBA, D-dimer; lower levels of ADAMTS 13 activity, ADAMTS13 activity: VWFAg, plasminogen activator inhibitor, tissue plasminogen activator. Moreover, 13/41 had clinical complications of SCD, five requiring hospitalization.

The Role of the von Willebrand Factor Collagen-Binding Assay (VWF:CB) in the Diagnosis and Treatment of von Willebrand Disease (VWD) and Way Beyond: A Comprehensive 36-Year History

The von Willebrand factor (VWF) collagen binding (VWF:CB) assay was first reported for use in von Willebrand diagnostics in 1986, by Brown and Bosak. Since then, the VWF:CB has continued to be used to help diagnose von Willebrand disease (VWD) (correctly) and also to help assign the correct subtype, as well as to assist in the monitoring of VWD therapy, especially desmopressin (DDAVP). However, it is important to recognize that the specific value of any VWF:CB is predicated on the use of an optimized VWF:CB, and that not all VWF:CB assays are so optimized. There are some good commercial assays available, but there are also some "not-so-good" commercial assays available, and these may continue to give the VWF:CB "a bad reputation." In addition to VWD diagnosis and management, the VWF:CB found purpose in a variety of other applications, from assessing ADAMTS13 activity, to investigation into acquired von Willebrand syndrome (especially as associated with use of mechanical circulatory support or cardiac assist devices), to assessment of VWF activity in disease states in where an excess of high-molecular-weight VWF may accumulate, and lead to increased (micro)thrombosis risk (e.g., coronavirus disease 2019, thrombotic thrombocytopenic purpura). The VWF:CB turns 37 in 2023. This review is a celebration of the utility of the VWF:CB over this nearly 40-year history.

Oral famotidine reduces the plasma level of soluble P-selectin in children with sickle cell disease

Plasma histamine levels are increased in patients with sickle cell disease (SCD), potentially promoting endothelial P-selectin expression and vaso-occlusion via histamine type 2 (H2) receptors. We conducted a prospective, non-comparative, single-centre study to determine whether famotidine, a H2 receptor antagonist, reduces P-selectin expression in SCD children. The median plasma P-selectin level was significantly reduced after 29 days of oral famotidine (53.2 ng/mL [IQR: 46.7-63.4] vs. 69.9 ng/mL [IQR: 53.6-84.2], median difference -10.2 ng/mL [IQR: -21.8 to -2.7], p = 0.005) in 28 patients. No effect was observed on other adhesion molecules, inflammation or haemolysis markers, except decreased reticulocyte count. No adverse events deemed related to famotidine were observed. Randomized controlled trials are now needed to assess the efficacy of famotidine in preventing vaso-occlusion in SCD.

VWF-ADAMTS13 axis dysfunction in children with sickle cell disease treated with hydroxycarbamide vs blood transfusion

Previous studies have reported elevated von Willebrand factor (VWF) levels in patients with sickle cell disease (SCD) and demonstrated a key role for the VWF-ADAMTS13 axis in the pathobiology of SCD vaso-occlusion. Although blood transfusion is the gold standard for stroke prevention in SCD, the biological mechanisms underpinning its improved efficacy compared with hydroxycarbamide are not fully understood. We hypothesized that the improved efficacy of blood transfusion might relate to differences in VWF-ADAMTS13 axis dysfunction. In total, 180 children with a confirmed diagnosis of SCD (hemoglobin SS) on hydroxycarbamide (n = 96) or blood transfusion (n = 84) were included. Despite disease-modifying treatment, plasma VWF and VWF propeptide were elevated in a significant proportion of children with SCD (33% and 47%, respectively). Crucially, all VWF parameters were significantly higher in the hydroxycarbamide compared with the blood transfusion cohort (P < .05). Additionally, increased levels of other Weibel-Palade body-stored proteins, including factor VIII (FVIII), angiopoietin-2, and osteoprotegerin were observed, indicated ongoing endothelial cell activation. Children treated with hydroxycarbamide also had higher FVIII activity and enhanced thrombin generation compared with those in the blood transfusion cohort (P < .001). Finally, hemolysis markers strongly correlated with VWF levels (P < .001) and were significantly reduced in the blood transfusion cohort (P < .001). Cumulatively, to our knowledge, our findings demonstrate for the first time that despite treatment, ongoing dysfunction of the VWF-ADAMTS13 axis is present in a significant subgroup of pediatric patients with SCD, especially those treated with hydroxycarbamide.

Hypercoagulability in Sickle Cell Disease: A Thrombo-Inflammatory Mechanism

Sickle cell disease (SCD) is a group of inherited disorders characterized by the presence of abnormal hemoglobin S. Patients with SCD suffer from frequent episodes of anemia, chronic hemolysis, pain crisis, and vaso-occlusion. Additionally, SCD is associated with diverse and serious clinical complications, including thrombosis, which can lead to organ failure, increased morbidity, and eventually, mortality. SCD is known to be a hypercoagulable condition, and the cause of hypercoagulability is multifactorial, with the molecular basis of hemoglobin S being the main driver. The presence of hemoglobin S induces sickling of the RBCs and their subsequent hemolysis, as well as oxidative stress. Both of these processes can alter the hemostatic system, through the activation of platelets, coagulation system, and fibrinolysis, as well as depletion of coagulation inhibitors. These changes can also induce the formation of microvesicles and expression of tissue factor, leading to activation of WBCs, endothelial cell damage, and inflammatory response. Understanding the various factors that drive hypercoagulability as a thrombo-inflammatory mechanism in SCD can help provide explanations for the pathogenesis and other complications of the disease.

Extracellular Vesicle Size Reveals Cargo Specific to Coagulation and Inflammation in Pediatric and Adult Sickle Cell Disease

Aberrant coagulation in sickle cell disease (SCD) is linked to extracellular vesicle (EV) exposure. However, there is no consensus on the contributions of small EVs (SEVs) and large EVs (LEVs) toward underlying coagulopathy or on their molecular cargo. The present observational study compared the thrombin potential of SEVs and LEVs isolated from the plasma of stable pediatric and adult SCD patients. Further, EV lipid and protein contents were analyzed to define markers consistent with activation of thrombin and markers of underlying coagulopathy. Results suggested that LEVs-but not SEVs-from pediatrics and adults similarly enhanced phosphatidylserine (PS)-dependent thrombin generation, and cell membrane procoagulant PS (18:0;20:4 and 18:0;18:1) were the most abundant lipids found in LEVs. Further, LEVs showed activated coagulation in protein pathway analyses, while SEVs demonstrated high levels of cholesterol esters and a protein pathway analysis that identified complement factors and inflammation. We suggest that thrombin potential of EVs from both stable pediatric and adult SCD patients is similarly dependent on size and show lipid and protein contents that identify underlying markers of coagulation and inflammation.

Contributions of von Willebrand factor to clinical severity of sickle cell disease: a systematic review and metanalysis

AIM

To evaluate the contributions of VWF to the clinical manifestation and severity of SCD.

DESIGN

A systematic review of peer-reviewed articles published in English. The review was carried out in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist.

METHODS

The data sources for the review included MEDLINE, PubMed, CINAHL, and Academic Search Complete. Articles that applied a quantitative approach to the investigation of the relationship of vWF with clinical manifestations and severity indices were included. The risk of bias assessment was carried out with a mixed-method appraisal tool. We computed I ² to estimate the degree of heterogeneity.

RESULT

There was a significantly higher level of VWF in SCD than in the control (d = 2.7, Z = 4.865, P < 0.001, I ² = 96.41%). Significant positive correlations were obtained for the relationship of VWF with vasoocclusive crisis (r= 0.277, Z= 5.077, P < 0.001, 1 ² =15.62), rate of hemolysis (r=0.441; Z= 4.440, I ² = <1%), extracellular haemoglobin (r=-0.397, Z=-4.155, I ² =<1%) and CRP (r = 0.331, Z = 4.566, P < 0.001, I ² < 1%).The VWF is important in determining the clinical severity of sickle cell disease, which constitutes a putative therapeutic target. More work is required to understand the causal direction underlying the association between VWF levels and the clinical severity of sickle cell disease and the potential role that VWF plays in the clinical manifestations of sickle cell disease.

PROTOCOL REGISTRATION

The protocol was registered with PROSPERO (CRD42021262625).

Association Between Patent Foramen Ovale and Overt Ischemic Stroke in Children With Sickle Cell Disease

Ischemic stroke is one of the most devastating complications of sickle cell anemia (SCA). Previous studies have shown that intracardiac shunting including patent foramen ovale (PFO) can be a potential risk factor for stroke in children with SCA. This study investigates the association between PFO and overt ischemic stroke in the DISPLACE (Dissemination and Implementation of Stroke Prevention Looking at the Care Environment) study cohort of 5,247 children with SCA of whom 1,414 had at least one clinical non-contrast transthoracic echocardiogram. Presence of PFO was taken from the clinical report. Further, we assessed the association between PFO and other clinical and hemolytic factors in children with SCA such as history of abnormal sickle stroke screen [elevated Transcranial Doppler ultrasound (TCD) velocity] and patient's baseline hemoglobin. In 642 children for whom all data were available, the adjusted odds ratio (OR) for overt stroke was higher in those with PFO but this was not statistically significant (OR: 1.49, 95% CI: 0.20-11.03, p = 0.6994). With an OR of 0.85, the study suggested less PFOs in those with abnormal TCD, but this was not statistically significant (95% CI: 0.17-4.25, p = 0.8463). Overall, the prevalence of PFO in this large sub study of non-contrast echocardiography amongst children with SCA is much lower than previous smaller studies using bubble contrast echocardiography. Overt stroke was non-statistically more common in children with SCA and PFO, but there was no evidence that PFO was more common in those with abnormal TCD, the most important pediatric sickle stroke screen.

Effect of hydroxyurea therapy on intravascular hemolysis and endothelial dysfunction markers in sickle cell anemia patients

Intravascular hemolysis (IH) contributes to the development of endothelial dysfunction (ED) in sickle cell anemia (SCA), and the effects of hydroxyurea (HU, the only approved drug that decreases the frequency and severity of vaso-oclussive crises) on IH and ED in SCA remain unclear. We evaluated and compared the markers of IH among steady-state adult Brazilians with SCA and HbAA individuals. Overall, this cross-sectional study enrolled 30 SCA patients not receiving HU therapy (HbSS), 25 SCA patients receiving HU therapy (HbSS_HU), and 32 HbAA volunteers (HbAA). The IH markers evaluated were serum Lactate Dehydrogenase (LDH), total heme, plasma hemoglobin (pHb), and soluble CD163 (sCD163). The ED markers analyzed were plasma von Willebrand factor (VWF:Ag), VWF ristocetin cofactor activity (VWF:RCo) levels, antigen of VWF-cleaving protease (ADAMTS13:Ag), thrombospondin-1, endothelin-1 levels, and ADAMTS13 Activity (ADAMTS13:Act). The levels of VWF:Ag, VWF:RCo, total heme, thrombospondin-1, and endothelin-1 were significantly higher in SCA patients (HbSS and HbSS_HU) compared to HbAA individuals. Also, pHb, LDH, and thrombospondin-1 levels were significantly higher in the HbSS group than in the HbSS_HU group. Contrarily, the levels of sCD163, ADAMTS13:Ag, and ADAMTS13:Act were significantly lower in both groups of SCA patients than HbAA controls, and ADAMTS13:Act levels were significantly lower in HbSS compared to HbSS_HU patients. The higher ADAMTS13 activity levels in those on HU therapy may be attributed to lower pHb and thrombospondin-1 levels as previously shown by in vitro studies that thrombospondin-1 and pHb are bound to VWF. Thus, VWF is restrained from ADAMTS13 activity and cleavage.

Sickle cell disease and COVID-19: Susceptibility and severity

We surveyed published papers and an international sickle cell disease (SCD) registry to detect susceptibility and clinical course of coronavirus disease 2019 (COVID-19) in SCD patients. COVID-19 presentation was mild in children and moderate in many SCD adults. Regarding increased comorbidities with age, it seems severe COVID-19 to be more common in older SCD patients. Although the overall outcome of COVID-19 was favorable in SCD children, a high rate of pediatric intensive care unit admission should be considered in managing these patients. To explain COVID-19 outcome in SCD patients, the possible benefits of hydroxyurea therapy could be considered. The obtained results should be interpreted, considering low cases from sub-Saharan people, younger age of SCD patients compared to general population, a bias toward registry of the more severe form of disease, the effect of pre-existing comorbidities with multisystem organ damage, and the role of health socio-economic determinants.

Relationship of Thrombospondin 1 to von Willebrand Factor and ADAMTS-13 in Sickle Cell Disease Patients of Arab Ethnicity

BACKGROUND

Thrombospondin 1 (TSP-1) is a multifunctional glycoprotein secreted by platelets. In sickle cell disease (SCD), TSP-1 promotes red cell adhesion to the endothelium by binding to von Willebrand factor (vWF) and inhibiting its degradation by the protease ADAMTS-13. We investigated a possible correlation between TSP-1, vWF and ADAMTS-13 in adult and pediatric SCD patients.

METHODS

Using commercially available ELISA kits, TSP-1, vWF and ADAMTS-13 levels were measured in 59 SCD patients (20 children and 39 adults) and compared with 59 age- and sex-matched controls. Associations between TSP-1 and parameters of interest were analyzed using Pearson's correlation coefficient.

RESULTS

Although TSP-1 levels were higher in adult and pediatric SCD patients than in controls, the increase was not statistically significant (p > 0.05). We found a significant positive correlation between TSP-1 and platelet count in both adult (r = 0.402, p = 0.01) and pediatric (r = 0.589, p = 0.01) patients, which is expected due to increased platelet activation in SCD. There was a positive correlation between TSP-1 and vWF in normal adults (r = 0.305, p = 0.049) and children (r = 0.633, p = 0.005) but not in patients (p > 0.05). A significant negative correlation between TSP-1 and ADAMTS-13 activity (r = -0.41, p = 0.01) was found in adult patients. Also, a significant negative correlation between TSP-1 and ADAMTS-13/vWF antigen ratio in both normal controls (r = -0.595, p = 0.009) and patients (r = -0.493, p = 0.032) is reported for the pediatric group.

CONCLUSIONS

Our findings confirm the inhibitory effects of TSP-1 on ADAMTS-13 activity in adult SCD patients. The negative correlation reported between TSP-1 and ADAMTS-13/vWF antigen ratio in pediatric subjects suggests a possible protective mechanism in younger individuals, although this is not related to the presence of SCD. This work emphasizes the impact of age on interpreting results related to the regulation of vWF expression and interaction with TSP-1 and ADAMTS-13 in SCD.

An evaluation of ticagrelor for the treatment of sickle cell anemia

INTRODUCTION

Ticagrelor is an antiplatelet agent approved for the treatment of patients with an acute coronary syndrome or a history of myocardial infarction. Considering the evidence demonstrating that ticagrelor-mediated inhibition of platelet activation and aggregation have beneficial effects in the treatment of thrombotic conditions, clinical studies have been conducted to evaluate the use of this drug for the treatment of sickle cell disease (SCD), demonstrating satisfactory tolerability and safety.

AREAS COVERED

Clinical investigation has characterized the pharmacokinetic and pharmacodynamical profile, as well as the efficacy and safety of ticagrelor to prevent painful vaso-occlusive crisis (painful episodes and acute chest syndrome) in SCD patients.

EXPERT OPINION

While phase 1 and 2 clinical trials demonstrated satisfactory tolerability and safety, the conclusion of phase 3 clinical trials is crucial to prove the efficacy of ticagrelor as a therapeutic option for the treatment of SCD. Thus, it is expected that ticagrelor, especially in combination with other drugs, will improve the clinical profile and quality of life of patients with SCD.

Sickle cell disease as a vascular disorder

INTRODUCTION

In sickle cell disease (SCD), hemoglobin S (HbS) red blood cells (RBCs) are characteristically deformed and inflexible. Often breaking down in the circulation, they exhibit increased adhesive properties with the endothelium and activated neutrophils and platelets, increasing the risk of occlusion of the microcirculation. SCD is categorized into two sub-phenotypes: hyperhemolytic, associated with priapism, leg ulcers, pulmonary hypertension, and stroke, and high hemoglobin/viscosity, which may promote vaso-occlusion-associated pain, acute chest syndrome, and osteonecrosis.

AREAS COVERED

The sub-phenotypes are not completely distinct. Hemolysis may trigger vaso-occlusion, contributing to vascular complications. Targeting P-selectin, a key mediator of cross-talk between hyperhemolysis and vaso-occlusion, may be beneficial for vascular and vaso-occlusion-associated complications. English-language articles from PubMed on the topic of SCD and vaso-occlusive crises (VOCs) were reviewed from 1 January 2000 to 1 January 2019 using the search terms 'sickle cell disease,' 'vaso-occlusive crises,' and 'selectin.'

EXPERT OPINION

Besides targeting P-selectin, other strategies to counter VOCs and RBC sickling are being pursued. These include platelet inhibition to counter aggregation, intercellular adhesion, and thrombosis during VOCs; gene therapy to correct the homozygous missense mutation in the β-globin gene, causing polymerization of HbS; L-glutamine, possibly reducing oxidative stress in sickled RBCs; and fetal hemoglobin inducers.

Methylene tetrahydrofolate reductase gene mutation in sickle cell anaemia patients in Lagos, Nigeria

Introduction

The significant causes of mortality among individuals with sickle cell anaemia (SCA) such as acute chest syndrome and cerebrovascular disease are related to vascular occlusion. Polymorphisms of the methylene tetrahydrofolate reductase (MTHFR) gene in persons with sickle cell anaemia have been suggested as a potential risk for vaso-occlusive events, with the C677T and A1298C polymorphisms being the commonest. This study therefore aimed to establish the pattern of MTHFR C677T and A1298C gene mutations among adults with HbSS phenotype attending the Haematology Clinic in Lagos State University Teaching Hospital Lagos, Nigeria.

Methods

A cross-sectional study was done among SCA patients attending the Haematology Clinic of the Lagos State University Teaching Hospital (LASUTH), using age and sex matched HbAA controls. DNA extraction and gene analysis were done. The selective amplification of a particular segment of the DNA by polymerase chain reaction (PCR) was done and subsequent digestion of the amplified MTHFR gene into its various fragments.

Results

The overall prevalence of the C677T mutation among participants was 19.3% (37 of 192), while the prevalence of A1298C was 15% (29 of 192).

Conclusion

The prevalence of MTHFR C677T was higher than A1298C mutations among sickle cell anaemia subjects.

Sickle Cell Disease and Stroke

Cerebral infarction is a common complication of sickle cell disease and may manifest as overt stroke or cognitive impairment associated with "silent" cerebral infarction on magnetic resonance imaging. Vasculopathy may be diagnosed on transcranial Doppler or magnetic resonance angiography. The risk factors in sickle cell disease for cognitive impairment, overt ischemic stroke, silent cerebral infarction, overt hemorrhagic stroke, and vasculopathy defined by transcranial Doppler or magnetic resonance angiography overlap, with severe acute and chronic anemia, acute chest crisis, reticulocytosis, and low oxygen saturation reported with the majority. However, there are differences reported in different cohorts, which may reflect age, geographic location, or neuroimaging techniques, for example, magnetic resonance imaging field strength. Regular blood transfusion reduces, but does not abolish, the risk of neurological complications in children with sickle cell disease and either previous overt stroke or silent cerebral infarction or abnormal transcranial Doppler. There are relatively few data on the use of hydroxyurea or other management strategies. Early assessment of the risk of neurocognitive complications is likely to become increasingly important in the management of sickle cell disease.

Current challenges in the management of patients with sickle cell disease - A report of the Italian experience

Sickle cell disease (SCD) is an inherited red blood cell disorder caused by a structural abnormality of hemoglobin called sickle hemoglobin (HbS). Clinical manifestations of SCD are mainly characterized by chronic hemolysis and acute vaso-occlusive crisis, which are responsible for severe acute and chronic organ damage. SCD is widespread in sub-Saharan Africa, in the Middle East, Indian subcontinent, and some Mediterranean regions. With voluntary population migrations, people harboring the HbS gene have spread globally. In 2006, the World Health Organization recognized hemoglobinopathies, including SCD, as a global public health problem and urged national health systems worldwide to design and establish programs for the prevention and management of SCD. Herein we describe the historical experience of the network of hemoglobinopathy centers and their approach to SCD in Italy, a country where hemoglobinopathies have a high prevalence and where SCD, associated with different genotypes including ß-thalassemia, is present in the native population.

Serum homocysteine and disease severity in sickle cell anemia patients in Lagos

Purpose: Hypercoagulability in sickle cell anemia (SCA) may be responsible for the increased development of vascular occlusion in certain organs as well as acute pain episodes. The causes of hypercoagulability in SCA are multifactorial and include raised homocysteine levels. This study, therefore, aimed to determine serum homocysteine levels in SCA patients in steady state and to correlate its levels with SCA disease severity. Patients and Methods: This was a cross-sectional study done among SCA patients in steady state attending the Haematology Clinic of the Lagos State University Teaching Hospital (LASUTH). Matched age and sex HbAA controls were also recruited. Serum homocysteine of each participant was done with enzyme-linked immunosorbent assay and disease severity score assessed in every SCA patient using clinical and laboratory parameters. Results: The mean value for homocysteine in the study group (SCA patients) was 19.80±19.75 µmol/L whilst that of the control group was 9.16±4.29 µmol/L. Thirty-nine out of 96 (46.6%) SCA patients had elevated homocysteine levels (>15 µmol/L) whilst all 96 participants in the control group had normal homocysteine levels. The difference in the means in the two groups was statistically significant with p=0.001. Majority (62.5%) of the SCA patients had a mild disease (severity score ≤3). There was a significant correlation between serum homocysteine levels and disease severity scores with p=0.04; χ2=4.04. Conclusion: Homocysteine levels were significantly higher in HbSS patients compared with matched HbAA controls and showed a positive correlation with disease severity scores in the SCA patients.

No evidence of increased cerebrovascular involvement in adult neurologically-asymptomatic β-Thalassaemia. A multicentre multimodal magnetic resonance study

Multi-factorial causes jeopardize brain integrity in β-thalassaemia. Intracranial parenchymal and vascular changes have been reported among young β-thalassaemia patients but conventional magnetic resonance imaging (MRI) findings are contradictory making early MRI and magnetic resonance angiography (MRA)/venography monitoring a matter of debate. This study prospectively investigated 75 neurologically asymptomatic β-thalassaemia patients (mean-age 35·2 ± 10·7 years; 52/75 transfusion-dependent; 41/75 splenectomised) using a 3T magnetic resonance scanner; clinical, laboratory and treatment data were also collected. White matter ischaemic-like abnormalities, intracranial artery stenoses, aneurysms and sinus venous thrombosis were compared between patients and 56 healthy controls (mean-age 33·9 ± 10·8 years). No patient or control showed silent territorial or lacunar strokes, intracranial artery stenoses or signs of sinus thrombosis. White matter lesions were found both in patients (35/75, 46·7%) and controls (28/56, 50·0%), without differences in terms of number (4·0 ± 10·6 vs. 4·6 ± 9·1, P = 0·63), size and Fazekas' Score. Intracranial aneurysms did not differ between patients and controls for incidence rate (7/75, 9·3% vs. 5/56, 8·9%), size and site. Vascular and parenchymal abnormality rate did not differ according to treatments or clinical phenotype. According to this study, asymptomatic β-thalassaemia patients treated according to current guidelines do not seem to carry an increased risk of brain and intracranial vascular changes, thus weakening recommendations for regular brain MRI monitoring.

Proteomic analysis of plasma from children with sickle cell anemia and silent cerebral infarction

Silent cerebral infarction is the most common neurological abnormality in children with sickle cell anemia, affecting 30-40% of 14 year olds. There are no known biomarkers to identify children with silent cerebral infarcts, and the pathological basis is also unknown. We used an unbiased proteomic discovery approach to identify plasma proteins differing in concentration between children with and without silent cerebral infarcts. Clinical parameters and plasma samples were analysed from 51 children (mean age 11.8 years, range 6-18) with sickle cell anemia (HbSS). A total of 19 children had silent cerebral infarcts and 32 normal MRI; the children with silent infarcts had lower HbF levels (8.6 vs. 16.1%, P=0.049) and higher systolic blood pressures (115 vs. 108.6, P=0.027). Plasma proteomic analysis showed 13 proteins increased more than 1.3 fold in the SCI patients, including proteins involved in hypercoagulability (α2-antiplasmin, fibrinogen−γ chain, thrombospondin-4), inflammation (α2-macroglobulin, complement C1s and C3), and atherosclerosis (apolipoprotein B-100). Higher levels of gelsolin and retinol-binding protein 4 were also found in the population with silent infarcts, both of which have been linked to stroke. We investigated the genetic basis of these differences by studying 359 adults with sickle cell disease (199 with silent cerebral infarcts, 160 normal MRIs), who had previously undergone a genome-wide genotyping array. None of the genes coding for the differentially expressed proteins were significantly associated with silent infarction. Our study suggests that silent cerebral infarcts in sickle cell anemia may be associated with higher systolic blood pressure, lower HbF levels, hypercoagulability, inflammation and atherosclerotic lipoproteins.

Biochemical markers in vascular cognitive impairment associated with subcortical small vessel disease - A consensus report

Background

Vascular cognitive impairment (VCI) is a heterogeneous entity with multiple aetiologies, all linked to underlying vascular disease. Among these, VCI related to subcortical small vessel disease (SSVD) is emerging as a major homogeneous subtype. Its progressive course raises the need for biomarker identification and/or development for adequate therapeutic interventions to be tested. In order to shed light in the current status on biochemical markers for VCI-SSVD, experts in field reviewed the recent evidence and literature data.

Method

The group conducted a comprehensive search on Medline, PubMed and Embase databases for studies published until 15.01.2017. The proposal on current status of biochemical markers in VCI-SSVD was reviewed by all co-authors and the draft was repeatedly circulated and discussed before it was finalized.

Results

This review identifies a large number of biochemical markers derived from CSF and blood. There is a considerable overlap of VCI-SSVD clinical symptoms with those of Alzheimer’s disease (AD). Although most of the published studies are small and their findings remain to be replicated in larger cohorts, several biomarkers have shown promise in separating VCI-SSVD from AD. These promising biomarkers are closely linked to underlying SSVD pathophysiology, namely disruption of blood-CSF and blood–brain barriers (BCB-BBB) and breakdown of white matter myelinated fibres and extracellular matrix, as well as blood and brain inflammation. The leading biomarker candidates are: elevated CSF/blood albumin ratio, which reflects BCB/BBB disruption; altered CSF matrix metalloproteinases, reflecting extracellular matrix breakdown; CSF neurofilment as a marker of axonal damage, and possibly blood inflammatory cytokines and adhesion molecules. The suggested SSVD biomarker deviations contrasts the characteristic CSF profile in AD, i.e. depletion of amyloid beta peptide and increased phosphorylated and total tau.

Conclusions

Combining SSVD and AD biomarkers may provide a powerful tool to identify with greater precision appropriate patients for clinical trials of more homogeneous dementia populations. Thereby, biomarkers might promote therapeutic progress not only in VCI-SSVD, but also in AD.

Therapeutic strategies in Sickle Cell Anemia: The past present and future

Sickle Cell Anemia (SCA) was one of the first hemoglobinopathies to be discovered. It is distinguished by the mutation-induced expression of a sickle cell variant of hemoglobin (HbS) that triggers erythrocytes to take a characteristic sickled conformation. The complex physiopathology of the disease and its associated clinical complications has initiated multi-disciplinary research within its field. This review attempts to lay emphasis on the evolution, current standpoint and future scope of therapeutic strategies in SCA.

Evaluation of von Willebrand factor and ADAMTS-13 antigen and activity levels in sickle cell disease patients in Kuwait

Sickle cell disease (SCD) is a severe form of hemolytic anemia characterized by chronic hemolysis and is associated with increased thrombotic risk. Elevated von Willebrand factor (vWF) levels in SCD have been attributed to increased secretion and impaired processing by its cleaving protease ADAMTS-13. In this study we measured vWF and ADAMTS-13 antigen and activity levels in our SCD patients. Hematological and biochemical parameters for 59 SCD patients (20 children and 39 adults) were analyzed and compared to 59 age- and sex-matched controls. Commercially available ELISA kits were used to measure vWF and ADAMTS-13 antigen and activity levels in patients and controls. Patients had significantly higher levels of vWF (p < 0.006) and ADAMTS-13 activity (p < 0.006) compared to controls. When patients were analyzed according to age and genotype, adult patients (23 SS and 16 Sβ⁰thal) maintained higher vWF antigen levels (p < 0.001), but with reduced ADAMTS-13 activity to vWF:Ag ratio (p < 0.003) compared to controls. Pediatric patients (8 SS and 12 Sβ⁰thal) had comparable vWF antigen levels to controls (p > 0.05), but had higher levels of ADAMTS-13 activity (p < 0.011) and ADAMTS-13 activity to vWF:Ag ratio (p < 0.038). Age is an important factor to consider when vWF and ADAMTS-13 proteins are analyzed among our patients. Increased vWF in adult patients may be attributed to increased production and resistance of vWF to proteolysis rather than ADAMTS-13 deficiency. This outcome was not seen in pediatric patients as higher ADAMTS-13 activity maintained vWF antigen at comparable levels to normal controls.

Increased prevalence of potential right-to-left shunting in children with sickle cell anaemia and stroke

'Paradoxical' embolization via intracardiac or intrapulmonary right-to-left shunts (RLS) is an established cause of stroke. Hypercoagulable states and increased right heart pressure, which both occur in sickle cell anaemia (SCA), predispose to paradoxical embolization. We hypothesized that children with SCA and overt stroke (SCA + stroke) have an increased prevalence of potential RLS. We performed contrasted transthoracic echocardiograms on 147 children (aged 2-19 years) with SCA + stroke) mean age 12·7 ± 4·8 years, 54·4% male) and a control group without SCA or stroke (n = 123; mean age 12·1 ± 4·9 years, 53·3% male). RLS was defined as any potential RLS detected by any method, including intrapulmonary shunting. Echocardiograms were masked and adjudicated centrally. The prevalence of potential RLS was significantly higher in the SCA+stroke group than controls (45·6% vs. 23·6%, P < 0·001). The odds ratio for potential RLS in the SCA + stroke group was 2·7 (95% confidence interval: 1·6-4·6) vs controls. In post hoc analyses, the SCA + stroke group had a higher prevalence of intrapulmonary (23·8% vs. 5·7%, P < 0·001) but not intracardiac shunting (21·8% vs. 18·7%, P = 0·533). SCA patients with potential RLS were more likely to report headache at stroke onset than those without. Intrapulmonary and intracardiac shunting may be an overlooked, independent and potentially modifiable risk factor for stroke in SCA.

Coagulation abnormalities of sickle cell disease: Relationship with clinical outcomes and the effect of disease modifying therapies

Sickle cell disease (SCD) is a hypercoagulable state. Patients exhibit increased platelet activation, high plasma levels of markers of thrombin generation, depletion of natural anticoagulant proteins, abnormal activation of the fibrinolytic system, and increased tissue factor expression, even in the non-crisis "steady state." Furthermore, SCD is characterized by an increased risk of thrombotic complications. The pathogenesis of coagulation activation in SCD appears to be multi-factorial, with contributions from ischemia-reperfusion injury and inflammation, hemolysis and nitric oxide deficiency, and increased sickle RBC phosphatidylserine expression. Recent studies in animal models suggest that activation of coagulation may contribute to the pathogenesis of SCD, but the data on the contribution of coagulation and platelet activation to SCD-related complications in humans are limited. Clinical trials of new generations of anticoagulants and antiplatelet agents, using a variety of clinical endpoints are warranted.

Contribution of Sickle Cell Disease to the Pediatric Stroke Burden Among Hospital Discharges of African-Americans-United States, 1997-2012

BACKGROUND

Approximately 10-20% of children with sickle cell disease (SCD) develop stroke, but few consistent national estimates of the stroke burden for children with SCD exist. The purpose of this study is to determine the proportion of diagnosed stroke among African-American pediatric discharges with and without SCD.

PROCEDURE

Records for African-Americans aged 1-18 years in the Kids' Inpatient Database (KID) 1997-2012 with ≥1 ICD-9-CM diagnosis code for stroke were included. Data were weighted to provide national estimates. A total of 2,994 stroke cases among African-American children were identified. Diagnoses co-existing with ischemic or hemorrhagic stroke were frequency ranked separately.

RESULTS

From 1997 through 2012, SCD was present in 24% of stroke discharges, with 89% being ischemic stroke. For hospital discharges of African-American children, SCD is the highest co-existing risk factor for ischemic stroke (29%). Stroke in children with SCD occurred predominantly in children aged 5-9 years, older than previously reported. The trend of stroke discharges significantly decreased for children with SCD from 1997 to 2012 for children aged 10-14 years.

CONCLUSIONS

SCD is a leading risk factor to pediatric stroke in African-American children. Reducing the number of strokes among children with SCD would have a significant impact on the rate of strokes among African-American children. Preventative intervention may be modifying initial age of presentation of stroke in children with SCD.

Risk factor analysis of cerebral white matter hyperintensities in children with sickle cell disease

Sickle cell disease (SCD) is complicated by silent cerebral infarcts, visible as white matter hyperintensities (WMHs) on magnetic resonance imaging (MRI). Both local vaso-occlusion, elicited by endothelial dysfunction, and insufficiency of cerebral blood flow (CBF) have been proposed to be involved in the aetiology. We performed an explorative study to investigate the associations between WMHs and markers of endothelial dysfunction and CBF by quantifying WMH volume on 3.0 Tesla MRI. We included 40 children with HbSS or HbSβ(0) thalassaemia, with a mean age of 12.1 ± 2.6 years. Boys demonstrated an increased risk for WMHs (odds ratio 4.5, 95% confidence interval 1.2-17.4), unrelated to glucose-6-phosphate dehydrogenase deficiency. In patients with WMHs, lower fetal haemoglobin (HbF) was associated with a larger WMH volume (regression coefficient = -0.62, R2 = 0.5, P = 0.04). Lower ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) levels were associated with lower CBF in the white matter (regression coefficient = 0.07, R2 = 0.15, P = 0.03), suggesting that endothelial dysfunction could potentially hamper CBF. The findings of our explorative study suggest that a high level of HbF may be protective for WMHs and that endothelial dysfunction may contribute to the development of WMHs by reducing CBF.

Effect of Chronic Blood Transfusion on Biomarkers of Coagulation Activation and Thrombin Generation in Sickle Cell Patients at Risk for Stroke

Hypercoagulability in sickle cell disease (SCD) is associated with multiple SCD phenotypes, association with stroke risk has not been well described. We hypothesized that serum levels of biomarkers of coagulation activation correlate with high transcranial Doppler ultrasound velocity and decreases with blood transfusion therapy in SCD patients. Stored serum samples from subjects in the Stroke Prevention in Sickle Cell Anemia (STOP) trial were analyzed using ELISA and protein multiplexing techniques. 40 subjects from each treatment arm (Standard Care [SC] and Transfusion [Tx]) at three time points—baseline, study exit and one year post-trial and 10 each of age matched children with SCD but normal TCD (SNTCD) and with normal hemoglobin (HbAA) were analyzed. At baseline, median vWF, TAT and D-dimer levels were significantly higher among STOP subjects than either HbAA or SNTCD. At study exit, median hemoglobin level was significantly higher while median TCD velocity was significantly lower in Tx compared to SC subjects. Median vWF (409.6 vs. 542.9 μg/ml), TAT (24.8 vs. 40.0 ng/ml) and D-dimer (9.2 vs. 19.1 μg/ml) levels were also significantly lower in the Tx compared to the SC group at study exit. Blood levels of biomarkers coagulation activation/thrombin generation correlated positively with TCD velocity and negatively with number of blood transfusions. Biomarkers of coagulation activation/thrombin generation were significantly elevated in children with SCD, at high risk for stroke. Reduction in levels of these biomarkers correlated with reduction in stroke risk (lower TCD velocity), indicating a possible role for hypercoagulation in SCD associated stroke.

What's new in the diagnosis and pathophysiology of thrombotic thrombocytopenic purpura

Severe ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) deficiency causes thrombotic thrombocytopenic purpura (TTP), which is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and the absence of oliguric or anuric renal failure. However, some patients with this constellation of findings do not have ADAMTS13 deficiency, and some patients with ADAMTS13 deficiency have renal failure or relatively normal blood counts. Consequently, many investigators and clinicians have incorporated severe ADAMTS13 deficiency into the case definition of TTP. This change has facilitated the timely initiation of treatment for patients with atypical clinical features who otherwise would not be recognized as having TTP. Conversely, excluding severe ADAMTS13 deficiency focuses attention on the diagnosis and treatment of other causes of thrombotic microangiopathy that require different treatment. The rapid return of ADAMTS13 data is important to make the best use of this information.