Sickle cell trait and the risk of venous thromboembolism among blacks

Hospital acquired venous thromboembolism in children with sickle cell disease

Sickle cell disease (SCD) is well recognized as a hypercoagulablestate, however, it remains unclear whether a subgroup of children with SCD at higher risk of venous thromboembolic event (VTE) during hospitalization may benefit from thromboprophylaxis. Our objectives were to describe the clinical characteristics, outcomes and recurrence of hospital acquired VTE in patients with SCD younger than 21 years. This was a single center retrospective study. Data regarding demographics, reason for admission, location of VTE, risk factors like central venous catheter (CVC), intensive care unit (ICU) admission among others were extracted from electronic medical records over a 10-year study period (2011-2021). Recurrence of VTE at 1 and 5 years was assessed. Descriptive statistics were used as indicated. We identified a total of 20 VTE events over the 10-year study period. Six of these events occurred in those younger than 12 years of age. Fourteen (70%) VTE events occurred in the HbSS or HbSβThal0 genotypes compared to 6 (30%) in HbSC. Most common VTE was isolated pulmonary embolism (PE) (n = 10, 50%). VTE were most often associated with acute chest syndrome (ACS) (n = 14, 70%), ICU admissions (n = 10, 50%) and CVC (n = 5/9, 55%). One patient died from the VTE event. One patient with additional underlying risk factors had a recurrent VTE at 13 months. Our study suggests that ICU admission, ACS and presence of CVC increases the risk of VTE in children and young adults with SCD, but larger studies are indicated to validate our findings.

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.

Understanding the role of red blood cells in venous thromboembolism: A comprehensive review

Traditionally, red blood cells (RBCs) have been perceived as passive entities within the fibrin network, without any significant role in the pathophysiology of venous thromboembolism (VTE). This review explores the involvement of RBCs in the VTE process, summarizing previous study findings and providing a comprehensive review of the latest theories. At first, it explores the influence of abnormal RBC counts (as seen in polycythemia vera and with erythropoietin use) and the exposure of RBCs to phosphatidylserine (Ptd-L-Ser) in the pathophysiology of VTE. The mechanisms of endothelial injury induced by RBCs and their adhesion to the endothelium under different disease models are then demonstrated. We explore the role of physical and chemical interactions between RBCs and platelets, as well as the interactions between RBCs and neutrophils - particularly the neutrophil extracellular traps (NETs) released by neutrophils - in the process of VTE. Additionally, we investigate the effect of RBCs on thrombin activation through two pathways, namely, the FXIIa-FXI-FIX pathway and the prekallikrein-dependent pathway. Lastly, we discuss the impact of RBCs on clot volume. In conclusion, we propose several potential methods aimed at unraveling the role of RBCs and their interaction with other components in the vascular system in the pathogenesis of VTE.

Thrombosis risk with haemoglobin C trait and haemoglobin C disease: A systematic review

The thrombotic risk with haemoglobin C trait (HbAC) or haemoglobin C disease (HbCC) is unclear. However, individuals with HbCC have demonstrated chronic haemolysis, higher blood viscosity and altered rheology when compared to individuals with wild-type haemoglobin (HbAA). These physiological alterations may theoretically translate to increased risk of thrombosis; therefore, a systematic literature review was performed to investigate the possible association between HbAC and/or HbCC and thrombosis. Twenty-two studies met inclusion criteria representing 782 individuals with HbAC (n = 694) or HbCC (n = 88). Fifteen studies described the presence/absence of venous thromboembolism (VTE) in patients with HbAC (n = 685) or HbCC (n = 79), while seven studies described patients with HbAC (n = 9) or HbCC (n = 9) and arterial thrombosis. Most (n = 20) studies were case reports or case series; however, two studies suggested a potential increased VTE risk with HbAC compared to HbAA in (i) all patients (OR 2.2, 95% CI: 0.9-5.5) and in (ii) pregnant individuals (RR 3.7, 95% CI 0.9-16). This review is the largest assessment of patients with HbC trait or disease and thrombosis to date; despite its limitations, the findings suggest HbC may be a predisposing risk factor to thrombosis. Prospective cohort studies are warranted to definitively elucidate the risk of thrombosis in this population.

Vaso-Occlusive Crises in Sickle Cell Trait Patients With Blood Loss Anemia: A Report of Two Cases

This report of two cases confronts the longstanding perception of Sickle Cell Trait (SCT) as a clinically benign condition, highlighting its complex and severe clinical manifestations, particularly in the context of blood loss anemia and vaso-occlusive crises (VOCs). The hallmark of sickle cell disease is the severe pain caused by acute vaso-occlusion of the microvasculature that leads to bone marrow infarction. We report two cases of patients with SCT and severe anemia in the setting of blood loss secondary to uterine fibroids subsequently causing VOCs with likely bone sequestration. The occurrence of VOCs in SCT, while infrequent, can be serious and demands a high index of suspicion, particularly when patients appear in significant distress and cardiac or vascular etiologies are ruled out as a source. Reversal of anemia in this case provided quick resolution to symptoms, and we recommend other clinicians not disregard a differential of VOC in SCT carriers, and urge to treat patients as they would if they had sickle cell disease. This report challenges the conventional view of SCT as a condition of clinical benignity, calling for a recalibration in the clinical understanding, management strategies, and focus on this genetic trait under similar circumstances.

Blood rheology and vascular function in sickle cell trait and sickle cell disease: From pathophysiological mechanisms to clinical usefulness

Sickle cell disease (SCD) is an autosomal recessive disorder. Although the molecular mechanisms at the origin of SCD have been well characterized, its clinical expression is highly variable. SCD is characterized by blood rheological abnormalities, increased inflammation and oxidative stress, and vascular dysfunction. Individuals with only one copy of the mutated β-globin gene have sickle cell trait (SCT) and are usually asymptomatic. The first part of this review focuses on the biological responses of SCT carriers during exercise and on the effects of combined SCT and diabetes on vascular function, several biomarkers and clinical complications. The second part of the review focuses on SCD and shows that the magnitude of red blood cell (RBC) rheological alterations is highly variable from one patient to another, and this variability reflects the clinical and hematological variability: patients with the less deformable RBCs have high hemolytic rate and severe anemia, and are prone to develop leg ulcers, priapism, cerebral vasculopathy, glomerulopathy or pulmonary hypertension. In contrast, SCD patients characterized by the presence of more deformable RBCs (but still rigid) are less anemic and may exhibit increased blood viscosity, which increases the risk for vaso-occlusive events. Several genetic and cellular factors may modulate RBC deformability in SCD: co-existence of α-thalassemia, fetal hemoglobin level, oxidative stress, the presence of residual mitochondria into mature RBCs, the activity of various non-selective cationic ion channels, etc. The last part of this review presents the effects of hydroxyurea and exercise training on RBC rheology and other biomarkers in SCD.

Sickle-Cell Trait as a Risk Factor for an Unprovoked Venous Thromboembolism: A Case Report

In this case report, we examine the increased risk of venous thromboembolism (VTE) in patients with sickle-cell trait (SCT), illustrated by a patient with SCT who developed pulmonary embolism (PE) despite low scores on conventional risk assessment tools. The case prompts both a discussion of risk assessment and management strategies in this population.

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.

Impact of Genetic Variations on Thromboembolic Risk in Saudis with Sickle Cell Disease

BACKGROUND

Sickle cell disease (SCD) is a Mendelian disease characterized by multigenic phenotypes. Previous reports indicated a higher rate of thromboembolic events (TEEs) in SCD patients. A number of candidate polymorphisms in certain genes (e.g., FVL, PRT, and MTHFR) were previously reported as risk factors for TEEs in different clinical conditions. This study aimed to genotype these genes and other loci predicted to underlie TEEs in SCD patients.

METHODOLOGY

A multi-center genome-wide association study (GWAS) involving Saudi SCD adult patients with a history of TEEs (n = 65) and control patients without TEE history (n = 285) was performed. Genotyping used the 10× Affymetrix Axiom array, which includes 683,030 markers. Fisher's exact test was used to generate p-values of TEE associations with each single-nucleotide polymorphism (SNP). The haplotype analysis software tool version 1.05, designed by the University of Göttingen, Germany, was used to identify the common inherited haplotypes.

RESULTS

No association was identified between the targeted single-nucleotide polymorphism rs1801133 in MTHFR and TEEs in SCD (p = 0.79). The allele frequency of rs6025 in FVL and rs1799963 in PRT in our cohort was extremely low (<0.01); thus, both variants were excluded from the analysis as no meaningful comparison was possible. In contrast, the GWAS analysis showed novel genome-wide associations (p < 5 × 10-8) with seven signals; five of them were located on Chr 11 (rs35390334, rs331532, rs317777, rs147062602, and rs372091), one SNP on Chr 20 (rs139341092), and another on Chr 9 (rs76076035). The other 34 SNPs located on known genes were also detected at a signal threshold of p < 5 × 10-6. Seven of the identified variants are located in olfactory receptor family 51 genes (OR51B5, OR51V1, OR51A1P, and OR51E2), and five variants were related to family 52 genes (OR52A5, OR52K1, OR52K2, and OR52T1P). The previously reported association between rs5006884-A in OR51B5 and fetal hemoglobin (HbF) levels was confirmed in our study, which showed significantly lower levels of HbF (p = 0.002) and less allele frequency (p = 0.003) in the TEE cases than in the controls. The assessment of the haplotype inheritance pattern involved the top ten significant markers with no LD (rs353988334, rs317777, rs14788626882, rs49188823, rs139349992, rs76076035, rs73395847, rs1368823, rs8888834548, and rs1455957). A haplotype analysis revealed significant associations between two haplotypes (a risk, TT-AA-del-AA-ins-CT-TT-CC-CC-AA, and a reverse protective, CC-GG-ins-GG-del-TT-CC-TT-GG-GG) and TEEs in SCD (p = 0.024, OR = 6.16, CI = 1.34-28.24, and p = 0.019, OR = 0.33, CI = 0.13-0.85, respectively).

CONCLUSIONS

Seven markers showed novel genome-wide associations; two of them were exonic variants (rs317777 in OLFM5P and rs147062602 in OR51B5), and less significant associations (p < 5 × 10-6) were identified for 34 other variants in known genes with TEEs in SCD. Moreover, two 10-SNP common haplotypes were determined with contradictory effects. Further replication of these findings is needed.

COVID-19 Infection and Outcomes in Newborn Screening Cohorts of Sickle Cell Trait and Sickle Cell Disease in Michigan and Georgia

The sickle cell mutation increases morbidity in those with sickle cell disease (SCD) and potentially sickle cell trait, impacting pulmonary, coagulation, renal, and other systems that are implicated in COVID-19 severity. There are no population-based registries for hemoglobinopathies, and they are not tracked in COVID-19 testing. We used COVID-19 test data from 2 states linked to newborn screening data to estimate COVID outcomes in people with SCD or trait compared with normal hemoglobin. We linked historical newborn screening data to COVID-19 tests, hospitalization, and mortality data and modeled the odds of hospitalization and mortality. Georgia's cohort aged 0 to 12 years; Michigan's, 0 to 33 years. Over 8% of those in Michigan were linked to positive COVID-19 results, and 4% in Georgia. Those with SCD showed significantly higher rates of COVID-19 hospitalization than the normal hemoglobin Black cohort, and Michigan had higher rates of mortality as well. Outcomes among those with the trait did not differ significantly from the normal hemoglobin Black group. People with SCD are at increased risk of COVID-19-related hospitalization and mortality and are encouraged to be vaccinated and avoid infection. Persons with the trait were not at higher risk of COVID-related severe outcomes.

Evaluating the Safety of Ultra-Low-Dose Estrogen Contraception in Sickle Cell Trait With Focus on Cerebral Venous Sinus Thrombosis

Ultra-low-dose combination estrogen-progestin contraceptive pills (OCP) have been marketed as being safer to use than previously higher estrogen-containing OCPs. While multiple large studies have shown a dose-dependent association between estrogen and deep vein thrombosis, there remains sparse guidance or data as to whether patients with sickle cell trait should avoid estrogen-containing OCPs regardless of the dosage. We present a case of a 22-year-old female with a history of sickle cell trait who had recently been started on an ultra-low-dose norethindrone-ethinyl estradiol-iron (1-20 mcg) that presented with headache, nausea, vomiting, and obtunded. Initial neuroimaging was significant for an extensive superior sagittal sinus thrombosis with extension into the confluence of dural venous sinuses, right transverse sinus, right sigmoid sinus, and right internal jugular vein which ultimately required systemic anti-coagulation. Her symptoms largely resolved within four days after starting anti-coagulation. She was discharged on day six to complete a six-month course of oral anti-coagulation. At her neurology follow-up three months later, the patient reported resolution of all symptoms. This study evaluates the safety of ultra-low-dose estrogen-containing contraceptive pills in the sickle cell trait population with special focus on cerebral sinus thrombosis.

Thrombosis in Pregnant Women with Hemolytic Anemia

Hemolytic anemias are a group of uncommon disorders affecting both genders, frequently occurring at the reproductive age. While a link between hemolysis and hypercoagulability has been suggested based on the elucidation of certain involved pathophysiological mechanisms, the extent of thrombotic risk in pregnant women with hemolytic anemia remains debatable. Due to the paucity of pregnancy-related data, risk assessment of gestations in women with hemolytic anemia is complicated. This review will highlight the latest advances in the diagnosis and management of these challenging disorders in pregnancy.

Deep Vein Thrombosis of the Left Lower Limb in a Sudanese Child with Sickle Cell Disease

This is a case of an eleven-year-old female Sudanese child, a known Sickle Cell Anemia (SCA) patient, who presented with fever, as well as left thigh and leg swelling that was associated with pain and warmness, which was diagnosed as Deep Vein Thrombosis (DVT) of her left lower limb. She had a previous history of admissions to the emergency room, during which she once received blood. The patient was managed by carrying out a basic routine initial laboratory investigation. A Doppler ultrasound scan showed features consistent with DVT. Based on the clinical findings and investigation results, management began by providing the patient with intravenous fluid, analgesia, packed Red Blood Cells (RBCs), intravenous antibiotics, and low-molecular-weight heparin. Further consultations showed that there was no need for vascular surgery or surgical intervention. This case highlights the need for more studies on DVT and Venous Thromboembolism (VTE) complications in children with SCA, so as to develop strategies for diagnosis and management in order to reduce the risk of life-threatening complications of VTE in patients with Sickle Cell Disease SCD.

Sudden Death in Diabetic Ketoacidosis Complicated by Sickle Cell Trait

ABSTRACT

In a sudden death investigation of a service member with sickle cell trait (SCT), evidence of sickle cell crisis further complicated by coexisting, undiagnosed diabetic ketoacidosis called into question the synergistic effects of diabetic ketoacidosis on red blood cell sickling. Sickle cell trait affects more than 4 million people in the United States (US) with the highest prevalence in non-Hispanic Blacks (7%-9%; Mil Med 2017;182(3):e1819-e1824). The heterozygous state of sickled hemoglobin was previously considered a benign condition causing sickling during hypoxic, high-stress conditions such as exercise and high altitude ( Am Assoc Clin Chem 2017). However, research within the last decade shows evidence of sudden death among SCT patients ( J Forensic Sci 2011;56(5):1352-1360). It has been shown that the presence of sickled hemoglobin artificially lowers levels of hemoglobin A1c making it a less effective biomarker for red blood cell glycosylation over time in sickle cell patients ( JAMA 2017;317(5):507-515). The limited scope of medical understanding of the effects of SCT in combination with other comorbidities requires further investigation and better diagnostic criteria. The uniqueness of the US Military and its screening program for sickle cell disease (SCD) and SCT allows for more detection. Since May 2006, newborn screening for SCD/SCT has been a national requirement; however, anyone older than 14 years may not know their SCD/SCT status ( Semin Perinatol 2010;34(2):134-44). The previous absence of such national screening makes it more challenging to identify SCT and SCD patients even within high-risk populations. Furthermore, patients may not know or understand the results of their SCD/SCT status testing. International standards for the autopsy of decedents with SCD and SCT exist ( R Coll Pathol 2017). Within the US, testing of vitreous electrolytes is a common practice in suspected natural death cases, but a review of the US literature did not demonstrate any autopsy standards or recommendations for persons with SCT or high-risk persons for sickling pathologies. The identification of a new diagnosis of type 2 diabetes mellitus, as the cause of death, is not uncommon; however, this case indicates that type 2 diabetes mellitus was not the sole contributing factor. It further illustrates that the US may be underestimating the impact of SCD and SCT as a cause of death, a contributing factor to death, and its synergistic effects with other pathologic processes. We propose a stringent literature review in conjunction with a review of international autopsy standards to develop national autopsy standards and possible SCT/SCD screening recommendations for high-risk persons at the time of autopsy.

Silent Infarcts, White Matter Integrity, and Oxygen Metabolic Stress in Young Adults With and Without Sickle Cell Trait

BACKGROUND

Individuals with sickle cell anemia have heightened risk of stroke and cognitive dysfunction. Given its high prevalence globally, whether sickle cell trait (SCT) is a risk factor for neurological injury has been of interest; however, data have been limited. We hypothesized that young, healthy adults with SCT would show normal cerebrovascular structure and hemodynamic function.

METHODS

As a case-control study, young adults with (N=25, cases) and without SCT (N=24, controls) underwent brain magnetic resonance imaging to quantify brain volume, microstructural integrity (fractional anisotropy), silent cerebral infarcts (SCI), intracranial stenosis, and aneurysms. Pseudocontinuous arterial spin labeling and asymmetric spin echo sequences measured cerebral blood flow and oxygen extraction fraction, respectively, from which cerebral metabolic oxygen demand was calculated. Imaging metrics were compared between SCT cases and controls. SCI volume was correlated with baseline characteristics.

RESULTS

Compared with controls, adults with SCT demonstrated similar normalized brain volumes (SCT 0.80 versus control 0.81, P=0.41), white matter fractional anisotropy (SCT 0.41 versus control 0.43, P=0.37), cerebral blood flow (SCT 62.04 versus control, 61.16 mL/min/100 g, P=0.67), oxygen extraction fraction (SCT 0.27 versus control 0.27, P=0.31), and cerebral metabolic oxygen demand (SCT 2.71 versus control 2.70 mL/min/100 g, P=0.96). One per cohort had an intracranial aneurysm. None had intracranial stenosis. The SCT cases and controls showed similar prevalence and volume of SCIs; however, in the subset of participants with SCIs, the SCT cases had greater SCI volume versus controls (0.29 versus 0.07 mL, P=0.008). Of baseline characteristics, creatinine was mildly elevated in the SCT cohort (0.9 versus 0.8 mg/dL, P=0.053) and correlated with SCI volume (ρ=0.49, P=0.032). In the SCT cohort, SCI distribution was similar to that of young adults with sickle cell anemia.

CONCLUSIONS

Adults with SCT showed normal cerebrovascular structure and hemodynamic function. These findings suggest that healthy individuals with SCT are unlikely to be at increased risk for early or accelerated ischemic brain injury.

Plasma Levels of Acyl-Carnitines and Carboxylic Acids Correlate With Cardiovascular and Kidney Function in Subjects With Sickle Cell Trait

Subjects with sickle cell trait (SCT) carry one copy of mutated β-globin gene at position E6V at the origin of the production of sickle hemoglobin (HbS). Indeed, individuals with SCT have both normal hemoglobin and HbS, in contrast to patients with sickle cell disease who inherited of two copies of the mutated gene. Although SCT is generally benign/asymptomatic, carriers may develop certain adverse outcomes such as renal complications, venous thromboembolism, exercise-induced rhabdomyolysis … However, little is known about whether similar metabolic pathways are affected in individuals with SCT and whether these metabolic derangements, if present, correlate to clinically relevant parameters. In this study, we performed metabolomics analysis of plasma from individuals with sickle cell trait (n = 34) compared to healthy controls (n = 30). Results indicated a significant increase in basal circulating levels of hemolysis markers, mono- (pyruvate, lactate), di- and tri-carboxylates (including all Krebs cycle intermediates), suggestive of systems-wide mitochondrial dysfunction in individuals with SCT. Elevated levels of kynurenines and indoles were observed in SCT samples, along with increases in the levels of oxidative stress markers (advanced glycation and protein-oxidation end-products, malondialdehyde, oxylipins, eicosanoids). Increases in circulating levels of acyl-carnitines and fatty acids were observed, consistent with increased membrane lipid damage in individuals with sickle cell trait. Finally, correlation analyses to clinical co-variates showed that alterations in the aforementioned pathways strongly correlated with clinical measurements of blood viscosity, renal (glomerular filtration rate, microalbuminuria, uremia) and cardiovascular function (carotid-femoral pulse wave velocity, blood pressure).

Circulating tissue factor-positive extracellular vesicles and their association with thrombosis in different diseases

Tissue factor (TF) is a procoagulant protein released from activated host cells, such as monocytes, and tumor cells on extracellular vesicles (EVs). TF + EVs are observed in the circulation of patients with various types of diseases. In this review, we will summarize the association between TF + EVs and activation of coagulation and survival in different types of diseases, including cancer, sepsis, and infections with different viruses, such as human immunodeficiency virus (HIV), influenza A virus (IAV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We will also discuss the source of TF + EVs in various diseases. EVTF activity is associated with thrombosis in pancreatic cancer patients and coronavirus disease 2019 patients (COVID-19) and with disseminated intravascular coagulation in cancer patients. EVTF activity is also associated with worse survival in patients with cancer and COVID-19. Monocytes are the major sources of TF + EVs in sepsis, and viral infections, such as HIV, Ebola virus, and SARS-CoV-2. In contrast, alveolar epithelial cells are the major source of TF + EVs in bronchoalveolar lavage fluid in COVID-19 and influenza A patients. These studies indicate that EVTF activity could be used as a biomarker to identify patients that have an increased risk of coagulopathy and mortality.

Venous thromboembolism prophylaxis in hospitalized sickle cell disease and sickle cell trait patients

INTRODUCTION

Sickle trait (Hb SA) or sickle disease (Hb SS) carries increased risk of venous thromboembolism (VTE). Hb SS patients are young and lack common comorbid conditions that qualify them for VTE prophylaxis (VTEP).

METHODS

Retrospective, multicenter analysis of Hb SS/Hb SA adult patients between January 2013 and December 2018.

RESULTS

There were 803 Hb SA (525 patients) and 1020 Hb SS admissions (262 patients). VTEP use was similar between Hb SA and controls (42% vs. 46%; p-value = .06) and Hb SS and controls (45% vs. 42%; p-value = .13). Hb SS/Hb SA patients more frequently received more than half of prescribed doses of VTEP. In multivariate analysis, increasing age and longer hospitalizations were positive predictors. Odds of VTEP use varied with treatment site for Hb SS patients, whereas comorbid conditions, admission hemoglobin and platelet count were not predictive. By contrast, in Hb SA patients, comorbid conditions, higher admission hemoglobin, and higher admission platelet counts raised the odds of VTEP being offered.

CONCLUSIONS

VTEP is underused in Hb SS/Hb SA patients. There may be a trend toward offering more VTEP in Hb SS disease, but not in Hb SA patients, where VTEP prescribing is driven by comorbid conditions rather than genotype. Patient compliance does not appear to play a major role, but intercenter variability suggests provider education may improve VTEP use.

First Experience in Living Liver Donation From Donors With Sickle Cell Trait

Living donor liver transplantation is the main source of organs in the Middle East. Therefore, well balanced criteria are needed to avoid unnecessary exclusion of potential donors, while prioritizing donor safety. We face a high incidence of sickle cell trait (SCT; and disease). Therefore, there is vast experience in general and cardiac surgeries in SCT carriers at our center. After studying their management in detail, we considered accepting SCT carriers as living liver donors, on an exceptional basis. This the first single-center case series of living donor liver transplantation with SCT.

Association of sickle cell trait with β-cell dysfunction and physical activity in adults living with and without HIV in Tanzania

This study aimed to investigate sickle cell trait (SCT) associations with physical activity, markers of insulin secretion and resistance, and glucose among people living with HIV infection (PLWH), both antiretroviral therapy (ART) naive and experienced, and HIV-uninfected adults. This was a cross-sectional study conducted in Mwanza, Northwestern Tanzania. We used data of 668 participants attained from two sub-studies of CICADA study. Mean age was 40 (SD 11.5) years, 402 (61.7%) were females and 157 (24.1%) had SCT. PLWH were 422 (64.7%), of these, 80 (18.9%) were on ART. People with SCT had higher risk of having an isolated β-cell dysfunction compared to those without SCT (RRR = 1.82, CI: 1.10, 3.01, p = 0.02). People with SCT but without HIV infection had lower average acceleration on the trunk longitudinal axis (ACCx) and higher level of self-reported physical activity. 30 min oral glucose tolerance test among PLWH on ART was higher in those with SCT compared to those without SCT. People with SCT are at higher risk of having β-cell dysfunction and those with SCT on ART are at more risk of developing diabetes. Future studies to investigate the interaction between SCT and HIV/ART on risk of diabetes should be considered.

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.

The Role of RBC Oxidative Stress in Sickle Cell Disease: From the Molecular Basis to Pathologic Implications

Sickle cell disease (SCD) is an inherited monogenic disorder and the most common severe hemoglobinopathy in the world. SCD is characterized by a point mutation in the β-globin gene, which results in hemoglobin (Hb) S production, leading to a variety of mechanistic and phenotypic changes within the sickle red blood cell (RBC). In SCD, the sickle RBCs are the root cause of the disease and they are a primary source of oxidative stress since sickle RBC redox state is compromised due to an imbalance between prooxidants and antioxidants. This imbalance in redox state is a result of a continuous production of reactive oxygen species (ROS) within the sickle RBC caused by the constant endogenous Hb autoxidation and NADPH oxidase activation, as well as by a deficiency in the antioxidant defense system. Accumulation of non-neutralized ROS within the sickle RBCs affects RBC membrane structure and function, leading to membrane integrity deficiency, low deformability, phosphatidylserine exposure, and release of micro-vesicles. These oxidative stress-associated RBC phenotypic modifications consequently evoke a myriad of physiological changes involved in multi-system manifestations. Thus, RBC oxidative stress in SCD can ultimately instigate major processes involved in organ damage. The critical role of the sickle RBC ROS production and its regulation in SCD pathophysiology are discussed here.

An investigation of sickle cell trait, body mass index, and fitness in relation to venous thromboembolism among African American adults

BACKGROUND

The relationships of sickle cell trait (SCT), body mass index (BMI), and physical fitness to venous thromboembolism (VTE) in young adults have received little attention.

OBJECTIVES

To test for associations among SCT, BMI, fitness, and VTE.

PATIENTS/METHODS

We conducted a retrospective cohort study of 48,316 SCT-tested, African American individuals in the US Army during 2011-14. We used Cox proportional hazards models to compute adjusted hazards of deep vein thrombosis (DVT) and pulmonary embolism (PE) associated with selected factors.

RESULTS

Incidence rates of DVT and PE were 1.09 and 0.91 cases per 1000 person-years, respectively. Adjusted hazard ratios (aHRs) for DVT for men and women with SCT were 0.9 (95% confidence interval [CI]: 0.4-2.0; P = .711) and 1.51 (CI: 0.7-3.2; P = .274), respectively. aHRs for PE for SCT+ men and women were 1.1 (CI: 0.5-2.4; P = .773) and 1.2 (CI: 0.5-3.1; P = .650), respectively. Low physical fitness was associated with DVT and PE in women (DVT aHR =3.1; CI: 1.4-6.5; P = .004; PE aHR =4.6; CI: 2.1-9.9; P < .001) and DVT in men (aHR =2.2; CI: 1.0-4.6; P = .048). Recent weight gain of 1 or more BMI points was associated with DVT in men (aHR =1.8; CI: 1.1-2.8; P = .017).

CONCLUSIONS

We found no evidence of increased VTE risk associated with SCT in this population. However, lower fitness levels and BMI increases were so associated.

Multiple thromboembolic events associated with bilateral superior vena cava and anomalous drainage into the left atrium

A 49-year-old female patient presented with acute-on-chronic chest pain. She was diagnosed with multiple systemic thromboemboli, including myocardial infarctions, bilateral chronic pulmonary emboli, ischaemic stroke, deep venous thrombosis and superficial thrombophlebitis. She had a background of sickle cell trait. Cardiac magnetic resonance showed bilateral superior vena cava (SVC). The right-sided SVC (RSVC) was joined by the right upper pulmonary vein and drained anomalously into the left atrium. This caused a small volume right to left shunt. The persistent left SVC drained into the right atrium (RA) via a dilated coronary sinus. The overall clinical impression was recurrent paradoxical emboli due to anomalous venous anatomy with a thrombophilia secondary to sickle cell trait. In the normal embryo, the right common cardinal vein develops to become the RSVC, which drains into the RA by term.

Association of Sickle Cell Trait With Incidence of Coronary Heart Disease Among African American Individuals

IMPORTANCE

The incidence of and mortality from coronary heart disease (CHD) are substantially higher among African American individuals compared with non-Hispanic White individuals, even after adjusting for traditional factors associated with CHD. The unexplained excess risk might be due to genetic factors related to African ancestry that are associated with a higher risk of CHD, such as the heterozygous state for the sickle cell variant or sickle cell trait (SCT).

OBJECTIVE

To evaluate whether there is an association between SCT and the incidence of myocardial infarction (MI) or composite CHD outcomes in African American individuals.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study included 5 large, prospective, population-based cohorts of African American individuals in the Women's Health Initiative (WHI) study, the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, the Multi-Ethnic Study of Atherosclerosis (MESA), the Jackson Heart Study (JHS), and the Atherosclerosis Risk in Communities (ARIC) study. The follow-up periods included in this study were 1993 and 1998 to 2014 for the WHI study, 2003 to 2014 for the REGARDS study, 2002 to 2016 for the MESA, 2002 to 2015 for the JHS, and 1987 to 2016 for the ARIC study. Data analysis began in October 2013 and was completed in October 2020.

EXPOSURES

Sickle cell trait status was evaluated by either direct genotyping or high-quality imputation of rs334 (the sickle cell variant). Participants with sickle cell disease and those with a history of CHD were excluded from the analyses.

MAIN OUTCOMES AND MEASURES

Incident MI, defined as adjudicated nonfatal or fatal MI, and incident CHD, defined as adjudicated nonfatal MI, fatal MI, coronary revascularization procedures, or death due to CHD. Cox proportional hazards regression models were used to estimate the hazard ratio for incident MI or CHD comparing SCT carriers with noncarriers. Models were adjusted for age, sex (except for the WHI study), study site or region of residence, hypertension status or systolic blood pressure, type 1 or 2 diabetes, serum high-density lipoprotein level, total cholesterol level, and global ancestry (estimated from principal components analysis).

RESULTS

A total of 23 197 African American men (29.8%) and women (70.2%) were included in the combined sample, of whom 1781 had SCT (7.7% prevalence). Mean (SD) ages at baseline were 61.2 (6.9) years in the WHI study (n = 5904), 64.0 (9.3) years in the REGARDS study (n = 10 714), 62.0 (10.0) years in the MESA (n = 1556), 50.3 (12.0) years in the JHS (n = 2175), and 53.2 (5.8) years in the ARIC study (n = 2848). There were no significant differences in the distribution of traditional factors associated with cardiovascular disease by SCT status within cohorts. A combined total of 1034 participants (76 with SCT) had incident MI, and 1714 (137 with SCT) had the composite CHD outcome. The meta-analyzed crude incidence rate of MI did not differ by SCT status and was 3.8 per 1000 person-years (95% CI, 3.3-4.5 per 1000 person-years) among those with SCT and 3.6 per 1000 person-years (95% CI, 2.7-5.1 per 1000 person-years) among those without SCT. For the composite CHD outcome, these rates were 7.3 per 1000 person-years (95% CI, 5.5-9.7 per 1000 person-years) among those with SCT and 6.0 per 1000 person-years (95% CI, 4.9-7.4 per 1000 person-years) among those without SCT. Meta-analysis of the 5 study results showed that SCT status was not significantly associated with MI (hazard ratio, 1.03; 95% CI, 0.81-1.32) or the composite CHD outcome (hazard ratio, 1.16; 95% CI, 0.92-1.47).

CONCLUSIONS AND RELEVANCE

In this cohort study, there was not an association between SCT and increased risk of MI or CHD in African American individuals. These disorders may not be associated with sickle cell trait-related sudden death in this population.

COVID-19 in Patients With Hematologic-Oncologic Risk Factors: Complications in Three Patients

The novel COVID-19 infection has demonstrated a spectrum of complications involving vascular, inflammatory, infectious, and metabolic conditions. These complications range from mild loss of smell to more severe acute respiratory distress syndrome (ARDS). Patients with more severe complications often require sedation and mechanical ventilation. Growing research has revealed the role of active malignancy and disease-in-remission status as possible risk factors contributing to the morbidity and mortality in COVID-19 patients. In our descriptive case series, we present three unique cases of complicated COVID-19 infection in patients with hematologic-oncologic risk factors and review the imaging features of their complications. The first patient was a 33-year-old male with sickle cell trait who developed rhabdomyolysis and myonecrosis of the paraspinal muscle in the setting of a physical fitness test; he subsequently developed an abscess at this site, presumably exacerbated by the hypoxemic state of his COVID-19 pneumonia. Our second patient was a 37-year-old male with COVID-19 pneumonia and a history of stage IV Non-Hodgkin's lymphoma in remission who developed spontaneous pneumomediastinum in the absence of positive pressure ventilation. The third COVID-positive patient was a 54-year-old male with a past medical history significant for grade 1 follicular non-Hodgkin's lymphoma in remission with sputum culture positive for mycobacterium avium complex and bronchoscopy positive for candida growth. 18-FDG/PET imaging was performed and demonstrated diffuse intense uptake throughout the lungs reflecting both the COVID-19 pneumonia and the multimicrobial superinfection.

The molecular basis for the prothrombotic state in sickle cell disease

The genetic and molecular basis of sickle cell disease (SCD) has long since been characterized but the pathophysiological basis is not entirely defined. How a red cell hemolytic disorder initiates inflammation, endothelial dysfunction, coagulation activation and eventually leads to vascular thrombosis, is yet to be elucidated. Recent evidence has demonstrated a high frequency of unprovoked/recurrent venous thromboembolism (VTE) in SCD, with an increased risk of mortality among patients with a history of VTE. Here, we thoroughly review the molecular basis for the prothrombotic state in SCD, specifically highlighting emerging evidence for activation of overlapping inflammation and coagulation pathways, that predispose to venous thromboembolism. We share perspectives in managing venous thrombosis in SCD, highlighting innovative therapies with the potential to influence the clinical course of disease and reduce thrombotic risk, while maintaining an acceptable safety profile.

[Sickle cell trait complications: A case series of 6 patients]

INTRODUCTION

Patients with sickle cell trait (SCT) are commonly considered as asymptomatic carriers. However, some clinical manifestations may occur.

METHODS

Here we present a retrospective descriptive study about SCT subjects with at least one complication diagnosed in a sickle cell disease referral center, in Paris, between 2008 and 2019. We also performed a literature review on the complications of SCT subjects.

RESULTS

Six patients (between 19 and 65 years old) were included. SCT was already known only for 4 of them at the time of the complication. Four patients presented with a splenic infarct after a stay in high altitude or a plane trip, one of them was associated with papillary necrosis; one patient had isolated papillary necrosis, and the last one had splenic sequestration. These complications happened for most of them after exposure to an unusual situation of hypoxia or deshydratation. Five out of 6 patients had a marked elevated C reactive protein.

CONCLUSION

SCT may cause acute ischemic complications in a context of prolonged hypoxia or dehydration. The most commonly reported are the splenic infarct and the renal papillary necrosis. A study of hemoglobin should be considered in these clinical situations in patients with compatible ethnic origin.

Pregnancy in sickle cell trait: what we do and don't know

Sickle cell trait (SCT) is the carrier state for sickle cell disease that results from the HBB rs334 missense mutation (p.Glu6Val) in the β-globin chain of haemoglobin. While not associated with any impact on life expectancy, it has been established that SCT is associated with an increased risk of both venous thromboembolism (and in particular, pulmonary embolism) and chronic kidney disease. It is largely unknown what short- or long-term effect, if any, pregnancy has upon the risk or outcomes of these disorders. In addition, SCT has been linked with various adverse outcomes in pregnancy, ranging from maternal complications such as elevated risk of bacteriuria to potentially life-threatening entities such as pre-eclampsia and prematurity. In these scenarios also, no clear association with SCT has been established. Given the high worldwide prevalence of SCT, further studies addressing these issues are warranted.

Sickle cell trait and the potential risk of severe coronavirus disease 2019-A mini-review

Coronavirus Disease 2019 (COVID‐19) pandemic is a rapidly evolving public health problem. The severity of COVID‐19 cases reported hitherto has varied greatly from asymptomatic to severe pneumonia and thromboembolism with subsequent mortality. An improved understanding of risk factors for adverse clinical outcomes may shed some light on novel personalized approaches to optimize clinical care in vulnerable populations. Emerging trends in the United States suggest possibly higher mortality rates of COVID‐19 among African Americans, although detailed epidemiological study data is pending. Sickle cell disease (SCD) disproportionately affects Black/African Americans in the United States as well as forebearers from sub‐Saharan Africa, the Western Hemisphere (South America, the Caribbean, and Central America), and some Mediterranean countries. The carrier frequency for SCD is high among African Americans. This article underscores the putative risks that may be associated with COVID‐19 pneumonia in sickle cell trait as well as potential opportunities for individualized medical care in the burgeoning era of personalized medicine.

Health outcomes and services in children with sickle cell trait, sickle cell anemia, and normal hemoglobin

The health effects of sickle cell trait among children are unknown. We compared select health outcomes and health services utilization among children with sickle cell trait, sickle cell anemia (SCA), and normal hemoglobin. Newborn screening records were used to identify children with sickle cell trait and SCA born in Michigan (1997-2014) who were enrolled in Michigan Medicaid for ≥1 year from 2012 to 2014. Each select health outcome (acute otitis media, acute respiratory infections, fever, invasive pneumococcal disease, pneumonia and influenza, renal complications, spleen problems, stroke) was defined as ≥1 claim with a diagnosis code for the respective outcome within a study year. Health services utilization was summarized as counts of emergency department, inpatient, and outpatient encounters. The relationship between hemoglobin status and each health outcome or utilization was assessed by logistic or negative binomial regression with generalized estimating equations. The study population consisted of 18 257 children with sickle cell trait, 368 with SCA, and 74 523 with normal hemoglobin (227 188 total person-years). Compared with those with normal hemoglobin, children with sickle cell trait had lower odds of acute otitis media (odds ratio [OR], 0.88; 95% confidence interval [CI], 0.84-0.91), acute respiratory infections (OR, 0.94; 95% CI, 0.92-0.97), pneumonia and influenza (OR, 0.93; 95% CI, 0.87-0.99), and outpatient visits (incidence rate ratio, 0.95; 95% CI, 0.93-0.97). Children with SCA had higher or nonsignificant odds of all outcomes and types of health services utilization. These results indicate that children with sickle cell trait may not be at additional health risk for these outcomes. However, additional case-control studies may be necessary to identify rare events.

Oxidative Stress and Thrombosis during Aging: The Roles of Oxidative Stress in RBCs in Venous Thrombosis

Mid-life stage adults are at higher risk of developing venous thrombosis (VT)/thromboembolism (VT/E). Aging is characterized by an overproduction of reactive oxygen species (ROS), which could evoke a series of physiological changes involved in thrombosis. Here, we focus on the critical role of ROS within the red blood cell (RBC) in initiating venous thrombosis during aging. Growing evidence has shifted our interest in the role of unjustifiably unvalued RBCs in blood coagulation. RBCs can be a major source of oxidative stress during aging, since RBC redox homeostasis is generally compromised due to the discrepancy between prooxidants and antioxidants. As a result, ROS accumulate within the RBC due to the constant endogenous hemoglobin (Hb) autoxidation and NADPH oxidase activation, and the uptake of extracellular ROS released by other cells in the circulation. The elevated RBC ROS level affects the RBC membrane structure and function, causing loss of membrane integrity, and decreased deformability. These changes impair RBC function in hemostasis and thrombosis, favoring a hypercoagulable state through enhanced RBC aggregation, RBC binding to endothelial cells affecting nitric oxide availability, RBC-induced platelet activation consequently modulating their activity, RBC interaction with and activation of coagulation factors, increased RBC phosphatidylserine exposure and release of microvesicles, accelerated aging and hemolysis. Thus, RBC oxidative stress during aging typifies an ultimate mechanism in system failure, which can affect major processes involved in the development of venous thrombosis in a variety of ways. The reevaluated concept of the critical role of RBC ROS in the activation of thrombotic events during aging will help identify potential targets for novel strategies to prevent/reduce the risk for VT/E or VT/E recurrences in mid-life stage adults.

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.

Thirty-year risk of ischemic stroke in individuals with sickle cell trait and modification by chronic kidney disease: The atherosclerosis risk in communities (ARIC) study

Sickle cell trait (SCT) has been associated with hypercoagulability, chronic kidney disease (CKD), and ischemic stroke. Whether concomitant CKD modifies long-term ischemic stroke risk in individuals with SCT is uncertain. We analyzed data from 3602 genotyped black adults (female = 62%, mean baseline age = 54 years) who were followed for a median 26 years by the Atherosclerosis Risk in Communities Study. Ischemic stroke was verified by physician review. Associations between SCT and ischemic stroke were analyzed using repeat-events Cox regression, adjusted for potential confounders. SCT was identified in 236 (7%) participants, who more often had CKD at baseline than noncarriers (18% vs 13%, P = .02). Among those with CKD, elevated factor VII activity was more prevalent with SCT genotype (36% vs 22%; P = .05). From 1987-2017, 555 ischemic strokes occurred in 436 individuals. The overall hazard ratio of ischemic stroke associated with SCT was 1.31 (95% CI: 0.95-1.80) and was stronger in participants with concomitant CKD (HR = 2.18; 95% CI: 1.16-4.12) than those without CKD (HR = 1.09; 95% CI: 0.74-1.61); P for interaction = .04. The hazard ratio of composite ischemic stroke and/or death associated with SCT was 1.20 (95% CI: 1.01-1.42) overall, 1.44 (95% CI: 1.002-2.07) among those with CKD, and 1.15 (95% CI: 0.94-1.39) among those without CKD; P for interaction = .18. The long-term risk of ischemic stroke associated with SCT relative to noncarrier genotype appears to be modified by concomitant CKD.

The current state of sickle cell trait: implications for reproductive and genetic counseling

Sickle cell trait (SCT) is unique among the carrier states that are identified during newborn screening. Unlike other heterozygous states for rare recessive diseases, SCT is exceedingly prevalent throughout regions of the world, making sickle cell disease one of the most common monogenetic diseases worldwide. Because of this high frequency, reproductive counseling is of paramount importance. In addition, unlike other carrier states, SCT seems to be a risk factor for several clinical complications, such as extreme exertional injury, chronic kidney disease, and venous thromboembolism. Increasing knowledge about these clinical outcomes can help inform genetic counseling recommendations. Expanding research and clinical efforts are needed to ensure that the promises of modern and precision medicine can be delivered to the millions of SCT carriers and their children.

Is There Any Improvement of the Coagulation Imbalance in Sickle Cell Disease after Hematopoietic Stem Cell Transplantation?

Several components of the clotting system are modified towards hypercoagulability in sickle cell disease (SCD). To date, hematopoietic stem cell transplantation (HSCT) is the only validated curative treatment of SCD. Here, we investigated the changes in the hemostatic potential of SCD children who've received a successful HSCT. Seventeen children with severe SCD were enrolled in the study. Thrombin generation (TG) was performed on citrated platelet-poor plasma, obtained before and 3, 6, 9, 12 and 15 months after HSCT. TG was triggered using 1 pM tissue factor and 4 µM phospholipids with or without thrombomodulin (TM). Before the HSCT, SCD children showed a higher endogenous thrombin potential (ETP), higher peak, higher velocity and shorter time-to-peak of TG than the normal controls (NC). ETP did not significantly change following the HSCT. However, the peak, velocity and time-to-peak of TG reversed to normal ranges from 3 months post-HSCT and remained so up to 15 months post-HSCT. The reduction of ETP after the addition of thrombomodulin (RETP) was dramatically reduced in SCD children before HSCT as compared with the NC. A partial reversal of RETP was observed from 3 months through 15 months post-HSCT. No statistical difference was observed for patient age or donor hemoglobinopathy status. In summary, successful HSCT improves the kinetics of TG but not the total thrombin capacity in SCD children.

Association of Sickle Cell Trait With Ischemic Stroke Among African Americans: A Meta-analysis

Importance

African Americans and individuals of African ancestry have a higher risk of stroke compared with non-Hispanic white individuals. Identifying the source of this disparity could provide an opportunity for clinical stroke risk stratification and more targeted therapy. Whether sickle cell trait (SCT) is an indicator of increased risk of ischemic stroke among African Americans is still unclear.

Objective

To examine whether SCT is associated with a higher risk of incident ischemic stroke among African Americans.

Design, Setting, and Participants

This meta-analysis assessed the association of SCT with the risk of incident ischemic stroke. Four large, prospective, population-based studies with African American cohorts were assessed: Jackson Heart Study (September 1, 2005, through December 31, 2012), Multi-Ethnic Study of Atherosclerosis (July 1, 2002, through December 31, 2012), Reasons for Geographic and Racial Differences in Stroke (January 1, 2003, through December 31, 2014), and Women's Health Initiative (October 1, 1998, through December 31, 2012). Using a Cox proportional hazards regression model adjusted for major stroke risk factors, this study estimated the hazard ratio for incident ischemic stroke associated with SCT. Data analysis was performed from July 10, 2016, to February 2, 2017.

Interventions or Exposures

Participants' SCT status determined by polymerase chain reaction assay genotyping or a combination of whole-exome sequencing and imputation.

Main Outcomes and Measures

Incident ischemic stroke.

Results

This meta-analysis included 19 464 African American individuals (1520 with SCT, 17 944 without SCT, and 620 with ischemic stroke) from 4 studies, with a mean (SD) age of 60.0 (13.0) years (5257 [27.0%] men and 14 207 [73.0%] women). No differences were found in the distribution of risk factors for ischemic stroke comparing participants with and those without SCT at study visit 1 in each cohort. The crude incidence of ischemic stroke was 2.9 per 1000 person-years (95% CI, 2.2-4.0 per 1000 person-years) among those with SCT and 3.2 per 1000 person-years (95% CI, 2.7-3.8 per 1000 person-years) among those without SCT. After stroke risk factors were adjusted for, the hazard ratio of incident ischemic stroke independently associated with SCT in the meta-analysis of all 4 cohorts was 0.80 (95% CI, 0.47-1.35; P = .82). The results of the meta-analysis were similar to those of individual cohorts, in which the results were also similar.

Conclusions and Relevance

Sickle cell trait may not be associated with incidence of ischemic stroke among African Americans. The results of this study suggest performing a more thorough clinical evaluation of a stroke patient with SCT rather than assuming that SCT is the etiologic factor for the stroke.

Association of sickle cell trait with atrial fibrillation: The REGARDS cohort

BACKGROUND

Sickle cell trait (SCT), sickle cell disease's (SCD) carrier status, has been recently associated with worse cardiovascular and renal outcomes. An increased prevalence of atrial fibrillation (AF) is documented in SCD patients; however, studies in individuals with SCT are lacking.

OBJECTIVES

To determine the association of SCT with AF.

METHODS

Among African-American participants in the REasons for Geographic and Racial Differences in Stroke (REGARDS) Study we assessed the association of SCT (by ECG or medical history) with prevalent AF using logistic regression adjusting for age, sex, income, education, history of stroke, myocardial infarction, diabetes, hypertension, and chronic kidney disease. A second evaluation was performed a mean of 9.2 years later among available participants, and the same model was used to test the association of SCT with incident AF.

RESULTS

In 10,409 participants with baseline ECG data and genotyping, 778 (7.5%) had SCT and 811 (7.8%) had prevalent AF. After adjusting for age, sex, education and income, SCT was associated with AF, OR 1.32 (95% CI 1.03-1.70). The association with incident AF assessed at the second in-home visit with the same adjustments was similar; OR 1.25 (95% CI 0.77-2.03).

CONCLUSIONS

SCT was associated with a higher prevalence of AF and a non-significantly higher incident AF over a 9.2 year period independent of AF risk factors. SCT remained associated with prevalent AF after adjusting for potential factors on the causal pathway such as hypertension and chronic kidney disease suggesting alternate mechanisms for the increased risk.

Sickle cell trait and risk of cognitive impairment in African-Americans: The REGARDS cohort

BACKGROUND

Sickle cell anemia may be associated with cognitive dysfunction, and some complications of sickle cell anemia might affect those with sickle cell trait (SCT), so we hypothesized that SCT is a risk factor for cognitive impairment.

METHODS

The Reasons for Geographic and Racial Differences in Stroke (REGARDS) study enrolled a national cohort of 30,239 white and black Americans from 2003 to 7, who are followed every 6 months. Baseline and annual global cognitive function testing used the Six-Item Screener (SIS), a validated instrument (scores range 0-6; ≤ 4 indicates cognitive impairment). Participants with baseline cognitive impairment and whites were excluded. Logistic regression was used to calculate the association of SCT with incident cognitive impairment, adjusted for risk factors. Linear mixed models assessed multivariable-adjusted change in test scores on a biennially administered 3-test battery measuring learning, memory, and semantic and phonemic fluency.

FINDINGS

Among 7743 participants followed for a median of 7·1 years, 85 of 583 participants with SCT (14·6%) developed incident cognitive impairment compared to 902 of 7160 (12·6%) without SCT. In univariate analysis, the odds ratio (OR) of incident cognitive impairment was 1·18 (95% CI: 0·93, 1·51) for those with SCT vs. those without. Adjustment did not impact the OR. There was no difference in change on 3-test battery scores by SCT status (all p > 0·11).

INTERPRETATION

In this prospective cohort study of black Americans, SCT was not associated with incident cognitive impairment or decline in test scores of learning, memory and executive function.

FUNDING

National Institutes of Health, American Society of Hematology.

Red blood cells modulate structure and dynamics of venous clot formation in sickle cell disease

Sickle cell disease (SCD) is associated with chronic activation of coagulation and an increased risk of venous thromboembolism. Erythrocyte sickling, the primary pathologic event in SCD, results in dramatic morphological changes in red blood cells (RBCs) because of polymerization of the abnormal hemoglobin. We used a mouse model of SCD and blood samples from sickle patients to determine if these changes affect the structure, properties, and dynamics of sickle clot formation. Sickling of RBCs and a significant increase in fibrin deposition were observed in venous thrombi formed in sickle mice. During ex vivo clot contraction, the number of RBCs extruded from sickle whole blood clots was significantly reduced compared with the number released from sickle cell trait and nonsickle clots in both mice and humans. Entrapment of sickled RBCs was largely factor XIIIa-independent and entirely mediated by the platelet-free cellular fraction of sickle blood. Inhibition of phosphatidylserine, but not administration of antisickling compounds, increased the number of RBCs released from sickle clots. Interestingly, whole blood, but not plasma clots from SCD patients, was more resistant to fibrinolysis, indicating that the cellular fraction of blood mediates resistance to tissue plasminogen activator. Sickle trait whole blood clots demonstrated an intermediate phenotype in response to tissue plasminogen activator. RBC exchange in SCD patients had a long-lasting effect on normalizing whole blood clot contraction. Furthermore, RBC exchange transiently reversed resistance of whole blood sickle clots to fibrinolysis, in part by decreasing platelet-derived PAI-1. These properties of sickle clots may explain the increased risk of venous thromboembolism observed in SCD.

Prevalence and risk factors for venous thromboembolism in children with sickle cell disease: an administrative database study

A hypercoagulable state resulting in increased venous thromboembolism (VTE) has been described in adults with sickle cell disease (SCD), but similar data for children are lacking. The objective of this retrospective cohort study was to describe the rate of VTE and risk factors associated with VTE in children with SCD across tertiary-care children's hospitals in the United States between the years 2009 and 2015. We used the Pediatric Health Information System database to investigate all pediatric patients with SCD admitted to 1 of 48 participating institutions between 1 January 2009 and 30 September 2015. International Classification of Disease, Ninth Edition, Clinical Modification codes were used to identify index thromboembolic events and chronic medical conditions known to be associated with VTE. Billing codes were used to identify central venous line (CVL) placement and pharmaceutical billing codes to identify estrogen containing oral-contraceptive use. Logistic regression analysis was used to study the association among unique patient characteristics, VTE, and death. 10 454 eligible subjects with SCD were identified. Median age (±interquartile range) of study cohort was 10 (±11) years. 181 subjects (1.7%) developed an index venous thromboembolic event during the study period. Median age at VTE diagnosis was 15.9 (±7.4) years. On multivariable logistic regression analysis, CVL placement, chronic renal disease, history of stroke, female sex, length of hospitalization, intensive care unit utilization, and older age were associated with VTE. After adjusting for other variables, VTE was independently associated with death. In summary, VTE can occur in pediatric patients with SCD. CVL placement is a modifiable risk factor for VTE development.

The current state of sickle cell trait: implications for reproductive and genetic counseling

Sickle cell trait (SCT) is unique among the carrier states that are identified during newborn screening. Unlike other heterozygous states for rare recessive diseases, SCT is exceedingly prevalent throughout regions of the world, making sickle cell disease one of the most common monogenetic diseases worldwide. Because of this high frequency, reproductive counseling is of paramount importance. In addition, unlike other carrier states, SCT seems to be a risk factor for several clinical complications, such as extreme exertional injury, chronic kidney disease, and venous thromboembolism. Increasing knowledge about these clinical outcomes can help inform genetic counseling recommendations. Expanding research and clinical efforts are needed to ensure that the promises of modern and precision medicine can be delivered to the millions of SCT carriers and their children.

Clinical Outcomes Associated With Sickle Cell Trait: A Systematic Review

Background

Although sickle cell trait (SCT) is largely a benign carrier state, it may increase risk for certain clinical outcomes.

Purpose

To evaluate associations between SCT and clinical outcomes in children and adults.

Data Sources

English-language searches of PubMed, CINAHL, the Cochrane Library, Current Contents Connect, Scopus, and Embase (1 January 1970 to 30 June 2018) and bibliographies of review articles.

Study Selection

Observational controlled studies (published in English) in children or adults that examined an association between SCT and any of 24 clinical outcomes specified a priori in the following 6 categories: exertion-related injury; renal, vascular, pediatric, and surgery- or trauma-related outcomes; and overall mortality.

Data Extraction

A single reviewer extracted study data, which was checked by another; 2 reviewers independently assessed study quality; and strength of evidence was assessed by consensus.

Data Synthesis

Of 7083 screened studies, 41 met inclusion criteria. High-strength evidence supported a positive association between SCT and risk for pulmonary embolism, proteinuria, and chronic kidney disease. Moderate-strength evidence supported a positive association between SCT and exertional rhabdomyolysis and a null association between SCT and deep venous thrombosis, heart failure or cardiomyopathy, stroke, and pediatric height or weight. Absolute risks for thromboembolism and rhabdomyolysis were small. For the remaining 15 clinical outcomes, data were insufficient or strength of evidence was low.

Limitation

Publication bias was possible, and high-quality evidence was scant.

Conclusion

Sickle cell trait is a risk factor for a few adverse health outcomes, such as pulmonary embolism, kidney disease, and exertional rhabdomyolysis, but does not seem to be associated with such complications as heart failure and stroke. Insufficient data or low-strength evidence exists for most speculated complications of SCT.

Primary Funding Source

National Human Genome Research Institute.

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.