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

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.

Evaluating thromboprophylaxis in the sickle cell disease population: Navigating the evidence gap

Sickle cell disease (SCD) arises from beta-globin gene mutations, with global estimates indicating around 500 000 affected neonates in 2021. In the United States, it is considered rare, impacting fewer than 200 000 individuals. The key pathogenic flaw lies in mutant haemoglobin S, prone to polymerization under low oxygen conditions, causing erythrocytes to adopt a sickled shape. This leads to complications like vascular occlusion, haemolytic anaemia, inflammation and organ damage. Beyond erythrocyte abnormalities however, there is a body of literature highlighting the hypercoagulable state that is likely a contributor to many of the complications we see in SCD. The persistent activation of the coagulation cascade results in thromboembolic events, notably venous thromboembolism (VTE) which is independently associated with increased mortality in both adults and children with SCD. While the increased risk of VTE in the SCD population seems well established, there is a lack of guidelines for thromboprophylaxis in this population. This Wider Perspective will describe the hypercoagulable state and increased thrombosis risk in the SCD population, as well as advocate for the development of evidence-based guidelines to aid in the prevention of VTE in SCD.

Assessment of menstrual health in adolescent and young adults with sickle cell disease

BACKGROUND

Sickle cell disease (SCD) is associated with hypercoagulability, but adults with SCD also have an increased incidence of bleeding including heavy menstrual bleeding (HMB). HMB is common among adolescent females, but the impact of HMB in pediatric SCD is unclear. The objectives of this study were to examine menstrual health status, knowledge, and quality of life (QOL).

METHODS

We performed a single-institutional multi-clinic cross-sectional study comprised of a five-part survey in pediatric participants with SCD. The survey included the validated Menstrual Bleeding Questionnaire (MBQ) and Self-administered Bleeding Assessment Tool (Self-BAT).

RESULTS

Forty-eight participants with a median age of 16 years (range: 12-21 years) completed the study. The mean age at onset of menarche was 13 ± 1.3 years. On the MBQ, 29% reported heavy/very heavy menstrual flow, 61% reported moderate or severe dysmenorrhea, and 96% had menses lasting less than 1 week. The Self-BAT revealed that 42% of participants reported a history of HMB. Participants with severe dysmenorrhea or HMB had higher MBQ scores, corresponding to worse QOL. Despite this, less than 20% of participants had attempted any hormonal therapy for menstrual regulation. The odds of hormonal therapy utilization were comparable among participants on hydroxyurea versus not on hydroxyurea (odds ratio 1.58, 95% confidence interval [CI]: 0.33-7.56).

CONCLUSIONS

The prevalence of HMB and dysmenorrhea is high among adolescents and young women with SCD. Strategies that incorporate menstrual health assessment into routine medical care in this population would help address this important area of pediatric health.

Venous thromboembolism prophylaxis practices for patients with sickle cell disease prior to and during the COVID-19 pandemic

Patients with sickle cell disease (SCD) are predisposed to a hypercoagulable state due to alterations in the coagulation system. Despite concern for the development of venous thromboembolism (VTE) in this population, there are no standardized guidelines for routine thromboprophylaxis. The objective of this study was to assess thromboprophylaxis practices of adult and pediatric treaters of SCD before and during the coronavirus disease of 2019 (COVID-19) pandemic. A cross-sectional electronic survey was distributed to pediatric and adult hematology oncology practitioners through seven SCD-specific interest groups between May 29, 2020, and July 13, 2020. Of 93 total responses, 14% ( N  = 13) reported they only treat patients more than 21 years old; 38.7% ( N  = 36) only treat patients 0-21 years old and 47.3% ( N  = 44) reported they treat both. Our study showed that before the COVID-19 pandemic, 96% of adult practitioners would recommend pharmacologic thromboprophylaxis, mechanical thromboprophylaxis or both for hospitalized adults with thromboprophylaxis, but only 76% of pediatric treaters would recommend any thromboprophylaxis in hospitalized children ( P  < 0.0001), with 24% of pediatric treaters choosing no thromboprophylaxis at all. During the COVID-19 pandemic, pharmacologic thromboprophylaxis specifically was recommended for adults by 94% of treaters and for pediatric patients by 76% of treaters. These findings suggest that despite the lack of evidence-based thromboprophylaxis guidelines in adults and children with thromboprophylaxis, subspecialty treaters routinely provide pharmacologic thromboprophylaxis in their adult patients and will modify their practice in pediatric patients who are considered at a high risk for VTE.

Pregnancy-related thromboembolism in women with sickle cell disease: An analysis of National Medicaid Data

Pregnancy and sickle cell disease (SCD) both individually carry a risk of thromboembolism (TE). Pregnancy in people with SCD may further enhance the prothrombotic effect of the underlying disease. The objectives of this study were to determine the rate and risk factors for arterial and venous thrombosis in pregnant people with SCD. Administrative claims data from the United States Centers for Medicare and Medicaid Service Analytic eXtract from 2006 to 2018 were used. The study population included people with SCD from the start of their first identified pregnancy until 1 year postpartum and a control cohort of pregnant people without SCD of similar age and race. Outcomes of interest were identified with ICD-9 or 10 codes. Logistic regression analyses were used to analyze risk factors. We identified infant deliveries in 6388 unique people with SCD and 17 110 controls. A total of 720 venous thromboembolism (11.3%) and 335 arterial TE (5.2%) were observed in people with SCD compared to 202 (1.2%) and 95 (0.6%) in controls. People with SCD had an 8-11 times higher odds of TE compared to controls (p < .001). Within the SCD cohort, age, hemoglobin SS (HbSS) genotype, hypertension, and history of thrombosis were identified as independent risk factors for pregnancy-related TE. Pregnancy-specific factors (pre-eclampsia, eclampsia, multigestational pregnancy) were not associated with TE. In conclusion, the risk of pregnancy-related TE is considerably higher in people with SCD compared with controls without SCD. Hence, people with SCD, particularly those with multiple risk factors may be candidates for thromboprophylaxis during pregnancy and the postpartum period.

The Role of Inflammation in The Cellular and Molecular Mechanisms of Cardiopulmonary Complications of Sickle Cell Disease

Cardiopulmonary complications remain the major cause of mortality despite newer therapies and improvements in the lifespan of patients with sickle cell disease (SCD). Inflammation has been identified as a major risk modifier in the pathogenesis of SCD-associated cardiopulmonary complications in recent mechanistic and observational studies. In this review, we discuss recent cellular and molecular mechanisms of cardiopulmonary complications in SCD and summarize the most recent evidence from clinical and laboratory studies. We emphasize the role of inflammation in the onset and progression of these complications to better understand the underlying pathobiological processes. We also discuss future basic and translational research in addressing questions about the complex role of inflammation in the development of SCD cardiopulmonary complications, which may lead to promising therapies and reduce morbidity and mortality in this vulnerable population.

Prevalence and Risk Factors for Pulmonary Embolism in Pediatric Sickle Cell Disease: A National Administrative Database Study

Patients with sickle cell disease (SCD) have a high risk for venous thromboembolism which is associated with increased risk of mortality. Studies examining risk of pulmonary embolism (PE) in children with SCD are lacking. This study was conducted in children with SCD between 0-21 years of age using a nationwide administrative database in the United States- Pediatric Health Information System (PHIS) from January 2010 to June 2021. Diagnostic codes and imaging, procedure, and pharmaceutical billing codes were used to identify PE and potential clinical, demographic, and utilization risk factors. Logistic regression analyses were performed to assess association between risk factors and PE. We identified 22,631 unique patients with SCD with a median age of 10.8 years (range: <0.1-20.9). A total of 120 (0.53%) patients developed a PE with median age of 17.4 years (range: 6.6-20.9) at PE diagnosis. Patients with PE had longer hospitalization and more frequent ICU admissions than patients without PE (p < 0.001). Risk factors significantly associated with PE on multivariable analysis included older age, prior history of central venous line (CVL), acute chest syndrome, and apheresis. Mortality was not significantly different between those with and without PE. The prevalence of PE in hospitalized children with SCD was estimated to be 0.53%. Patients with PE had higher healthcare utilization characteristics. Factors significantly associated with PE suggest that the risk for PE in SCD may be related to the severity of disease state. Future trials are needed for risk stratification and PE prevention strategies in children with SCD.

Sex as an Independent Risk Factor for Venous Thromboembolism in Sickle Cell Disease: A Cross-Sectional Study

Venous thromboembolism (VTE) affects up to 25% of individuals with sickle cell disease (SCD), but risk factors are not well characterized. We sought to measure the prevalence of VTE among SCD patients in our health system and to describe the relationship between medical history, biological sex, and VTE. We performed a retrospective chart review of SCD patients who visited an outpatient hematology clinic within Penn Medicine between June 2014 and June 2019. Demographics and medical history were compared across those with and without a history of VTE. We developed a logistic regression model to describe factors independently associated with VTE. Of 597 patients with SCD who were identified, 147 (24.6%) had a history of VTE; 100 were female and 47 were male. In the regression model, female sex was independently associated with history of VTE (odds ratio 1.91, 95% confidence interval 1.26-2.91), as were pulmonary hypertension, hydroxyurea use, and history of stroke. Among females only, 49.7% were parous and 18.8% had used oral contraceptives, and these proportions did not differ by history of VTE. One-quarter of the SCD patients in our health system had a history of VTE, confirming significantly higher rates than in the general population. Females had twice the odds of VTE compared to males, highlighting an important sex disparity in SCD disease outcomes and raising questions regarding optimal pregnancy and contraceptive care for females with SCD.

A Patient with Sickle Cell Disease and Recurrent Venous Thromboembolism after Renal Transplantation

Venous thromboembolism (VTE) is a life-threatening complication, especially in case of recurrence. The appropriate duration of anticoagulant treatment following the first event is crucial. Risk factors that increase the risk of recurrence of VTE are many, and include medications, kidney disease, renal transplantation (RT), and a diagnosis of sickle cell disease (SCD). There are currently no guidelines that define the duration of anticoagulant therapy after the first event in a patient with RT. We report a case of recurring episodes of VTE after RT in a SCD patient. Our case suggests that the use of a long-term anticoagulant treatment may be recommended in patients with SCD and RT after the first event of VTE.

Sickle Cell Disease: A Review

IMPORTANCE

Sickle cell disease (SCD) is an inherited disorder of hemoglobin, characterized by formation of long chains of hemoglobin when deoxygenated within capillary beds, resulting in sickle-shaped red blood cells, progressive multiorgan damage, and increased mortality. An estimated 300 000 infants are born annually worldwide with SCD. Most individuals with SCD live in sub-Saharan Africa, India, the Mediterranean, and Middle East; approximately 100 000 individuals with SCD live in the US.

OBSERVATIONS

SCD is diagnosed through newborn screening programs, where available, or when patients present with unexplained severe atraumatic pain or normocytic anemia. In SCD, sickling and hemolysis of red blood cells result in vaso-occlusion with associated ischemia. SCD is characterized by repeated episodes of severe acute pain and acute chest syndrome, and by other complications including stroke, chronic pain, nephropathy, retinopathy, avascular necrosis, priapism, and leg ulcers. In the US, nearly all children with SCD survive to adulthood, but average life expectancy remains 20 years less than the general population, with higher mortality as individuals transition from pediatric to adult-focused health care systems. Until 2017, hydroxyurea, which increases fetal hemoglobin and reduces red blood cell sickling, was the only disease-modifying therapy available for SCD and remains first-line therapy for most individuals with SCD. Three additional therapies, L-glutamine, crizanlizumab, and voxelotor, have been approved as adjunctive or second-line agents. In clinical trials, L-glutamine reduced hospitalization rates by 33% and mean length of stay from 11 to 7 days compared with placebo. Crizanlizumab reduced pain crises from 2.98 to 1.63 per year compared with placebo. Voxelotor increased hemoglobin by at least 1 g/dL, significantly more than placebo (51% vs 7%). Hematopoietic stem cell transplant is the only curative therapy, but it is limited by donor availability, with best results seen in children with a matched sibling donor. While SCD is characterized by acute and chronic pain, patients are not more likely to develop addiction to pain medications than the general population.

CONCLUSIONS AND RELEVANCE

In the US, approximately 100 000 people have SCD, which is characterized by hemolytic anemia, acute and chronic pain, acute chest syndrome; increased incidence of stroke, nephropathy, and retinopathy; and a life span that is 20 years shorter than the general population. While hydroxyurea is first-line therapy for SCD, L-glutamine, crizanlizumab, and voxelotor have been approved in the US since 2017 as adjunctive or second-line treatments, and hematopoietic stem cell transplant with a matched sibling donor is now standard care for severe disease.

Prevalence of venous thromboembolism and its associations in a large racially homogenous population of sickle cell disease patients

To determine the prevalence of venous thromboembolism (VTE) among adult sickle cell disease (SCD) patients in Nigeria.

METHODS

This was a multicentre retrospective study in which the medical records of adult SCD patients were reviewed. Information on demographics, steady-state haemogram, clinical phenotypes, duration of follow-up, history of VTE including risk factors and management was collected.

RESULTS

Of the 509 SCD patients with a median (IQR) duration of follow-up of 2 years, 10 (2.0%) had VTE (9 DVT and 1 PE). Their median (IQR) age was 27 (22.8-30.3) years. Identifiable risk factors for VTE included positive family history (2, 20%) surgery, splenectomy, paraplegia and cancer (1, 10% each). No risk factor was identifiable in four persons. VTE had no significant association with age and gender. VTE was significantly associated with the following events: acute chest syndrome [p = .002, odds ratio (OR) 8, 95% CI 2.2-28.9], osteonecrosis [p = .012, OR 5.24, 95% CI, 1.45-18.91] and vaso-occlusive crisis [p = .035]. Also significantly associated with VTE were pulmonary hypertension [p = .001, OR 23.3, 95%CI 5.18-105.06] and stroke [p = .032, OR 9.35, 95%CI 0.87-53.25].

CONCLUSION

The prevalence of VTE among SCD patients in Nigeria is low. It is significantly associated with vaso-occlusive crisis, pulmonary hypertension and stroke.

Predicting risk factors for thromboembolic complications in patients with sickle cell anaemia - lessons learned for prophylaxis

Objective

To assess the clinical and laboratory predictors of venous thromboembolism (VTE) in patients with sickle cell anaemia (SCA) and its relationship to morbidity and mortality.

Methods

This retrospective case–control study analysed data from patients with SCA that experienced VTE compared with matched control patients with SCA but no VTE (2:1 ratio).

Results

A total of 102 patients with SCA were enrolled (68 cases with VTE and 34 controls). Amongst the 68 cases (median age, 29.5 years), 26 (38.2%) presented with isolated pulmonary embolism (PE). A higher prevalence of splenectomy (73.5% versus 35.3%) was observed in the cases compared with the controls. A significantly higher prevalence of central venous catheter (CVC) insertion (42.6% versus 8.8%) was observed in the cases compared with the controls. High white blood cell counts, serum lactic dehydrogenase (LDH), bilirubin and C-reactive protein (CRP) and low haemoglobin (Hb) and HbF were significant risk factors for VTE. Forty-two cases (61.8%) developed acute chest syndrome, 10 (14.7%) had a stroke and seven (10.3%) died.

Conclusions

VTE in patients with SCA has a high impact on morbidity and mortality. PE was the leading presentation of VTE, with CVC insertion, high LDH, bilirubin, CRP and white blood cell counts along with low Hb and HbF constituting other significant risk factors.

How we approach thrombosis risk in children with COVID-19 infection and MIS-C

Thrombosis within the microvasculature and medium to large vessels is a serious and common complication among critically ill individuals with coronavirus disease 2019 (COVID-19). While children are markedly less likely to develop severe disease than adults, they remain at risk for thrombosis during acute infection and with the post-acute inflammatory illness termed multisystem inflammatory syndrome in children. Significant knowledge deficits in understanding COVID-19-associated coagulopathy and thrombotic risk pose clinical challenges for pediatric providers who must incorporate expert opinion and personal experience to manage individual patients. We discuss clinical scenarios to provide framework for characterizing thrombosis risk and thromboprophylaxis in children with COVID-19.

Pediatric Hematologic and Oncologic Emergencies

Pediatric hematologic and oncologic emergencies are in 3 major categories: complications of hematologic disorders, emergencies associated with the new onset of cancers, and treatment-associated oncologic emergencies. The overall number of these patients remains low; however, the mortality associated with these diseases remains high despite significant advances in management. This article presents a review of the most commonly encountered pediatric hematologic and oncologic complications that emergency physicians and providers need to know.

Clinical, laboratory, and genetic risk factors for thrombosis in sickle cell disease

Sickle cell disease (SCD) patients are at a four- to 100-fold increased risk for thrombosis compared with the general population, although the mechanisms and risk factors are not clear. We investigated the incidence and predictors for thrombosis in a retrospective, longitudinal cohort of 1193 pediatric and adult SCD patients treated at our institution between January 2008 and December 2017. SCD diagnosis and thrombotic complications were identified using International Classification of Diseases coding and verified through medical chart review. Clinical and laboratory data were extracted from the medical records. With a median follow-up of 6.4 years, 208 (17.4%) SCD patients experienced 352 thrombotic events (64 strokes, 288 venous thromboembolisms [VTE]). Risk factors for stroke included older age and HbSS/Sβ0-genotype and a lower hemoglobin (Hb) F% in the subset of HbSS/Sβ0-genotype patients (P < .05). VTE risk was independently associated with lower estimated glomerular filtration rate, hydroxyurea (HU) use, HbSS/Sβ0 genotype, and higher white blood cell (WBC) counts and Hb (P ≤ .03). Two thrombomodulin gene variants previously associated with thrombosis in the general African American population, THBD rs2567617 (minor allele frequency [MAF] 0.25; odds ratio [OR], 1.5; P = .049) and THBD rs1998081 (MAF, 0.24; OR, 1.5; P = .059), were associated with thrombosis in this cohort. In summary, thrombotic complications are common, and several traditional and SCD-specific risk factors are associated with thrombotic risk. Future studies integrating clinical, laboratory, and genetic risk factors may improve our understanding of thrombosis and guide intervention practices in SCD.

Venous Thromboembolism among Noncritically Ill Hospitalized Children: Key Considerations for the Pediatric Hospital Medicine Specialist

Venous thromboembolism (VTE) is a leading cause of morbidity and preventable harm among noncritically ill hospitalized children. Several clinical factors relevant to the noncritically ill hospitalized child significantly increase the risk of VTE including the presence of central venous catheters, systemic inflammation, and prolonged immobilization. Although risk mitigation strategies have been described, the diagnosis, treatment, and prevention of VTE require standardization of institutional practices combined with multidisciplinary collaboration among pediatric hospitalists, hematologists, and other care providers. In this narrative review, we summarize the epidemiology of VTE, risk models identifying high-risk conditions associated with VTE, and prevention and treatment strategies. We further describe successful quality improvement efforts implementing institutional VTE risk stratification and thromboprophylaxis procedures. Finally, we highlight unique challenges facing pediatric hospital medicine specialists in the era of the COVID-19 pandemic, including caring for adults admitted to pediatric hospital units, and describe future research opportunities for VTE in the noncritically ill hospitalized child.

Venous thromboembolism in children with central nervous system tumors: Comparison of an institutional cohort to a national administrative database

BACKGROUND

Central nervous system (CNS) tumors are the second most common malignancy of childhood, and published data on venous thromboembolism (VTE) rate and risk factors for these patients are outdated or incomplete. Here, we determine the cumulative incidence and risk factors for VTE in this population.

PROCEDURE

VTE diagnosis and associated clinical risk factors were abstracted and analyzed for two cohorts of children (0-21 years) diagnosed with CNS tumors between January 1, 2010 to September 30, 2018. The first study was a retrospective single institution cohort study. The initial observations were confirmed across multiple pediatric hospitals using the Pediatric Health Information System (PHIS) administrative database.

RESULTS

The single-institution cohort included 338 patients aged 3 days to 20.9 years (median age, 8.6 years); VTE developed in eight (2.4%) patients. The PHIS cohort included 17 634 patients aged from 0 to 21.9 years (median: 9.5 years); VTE developed in 354 (2.0%) patients. Univariate analysis for the single-institution cohort identified central venous catheter (CVC) placement as a risk factor for VTE (odds ratio [OR] 8.40, 95% confidence interval [CI] 1.43-49.41, P = .0186). Multivariable analysis of the PHIS dataset identified CVC placement (OR 1.97, 95% CI 1.57-2.46; P < .0001), obesity (OR 2.96, 95% CI 1.21-7.26; P = .0177), and more than one hospital admission (OR 3.54, 95% CI 2.69-4.64; P < .0001) as significant predictors of VTE. VTE diagnosis was not associated with increased mortality in either cohort.

CONCLUSIONS

The VTE rate in children with CNS tumors is low (2%). CVC placement was identified as a modifiable risk factor in both cohorts.

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.

Current Issues and Options for Hormonal Contraception in Adolescents and Young Adult Women With Sickle Cell Disease: An Update for Health Care Professionals

Women with sickle cell disease (SCD) are of particular concern regarding the significantly increased risk of pregnancy-related morbidity, mortality, and adverse outcomes. They have limited knowledge of pregnancy and childbirth risks, as well as of the benefits and risks of contraceptives. Thus, there is an urgent need for appropriate information about reproductive family planning to reduce unintended pregnancy. Any decision regarding the use of contraceptives has to be based on the efficacy and risk/benefit ratio of the method used. Both the World Health Organization (WHO) and the Centers for Disease Control (CDC) have developed, published, and updated evidence-based guidelines for medical providers for the use of contraceptives in patients with specific medical chronic conditions. This article provides an overview of the present knowledge on the use of contraceptives in women with SCD. We believe that the collaboration between health care professionals (hematologists, obstetricians, endocrinologists, and primary care providers) can play a major role in identifying the safer contraceptive method to abolish the risks of unintended pregnancy and preserve the health status of patients with SCD.

American Society of Hematology 2019 guidelines for sickle cell disease: cardiopulmonary and kidney disease

BACKGROUND

Prevention and management of end-organ disease represent major challenges facing providers of children and adults with sickle cell disease (SCD). Uncertainty and variability in the screening, diagnosis, and management of cardiopulmonary and renal complications in SCD lead to varying outcomes for affected individuals.

OBJECTIVE

These evidence-based guidelines of the American Society of Hematology (ASH) are intended to support patients, clinicians, and other health care professionals in their decisions about screening, diagnosis, and management of cardiopulmonary and renal complications of SCD.

METHODS

ASH formed a multidisciplinary guideline panel that included 2 patient representatives and was balanced to minimize potential bias from conflicts of interest. The Mayo Evidence-Based Practice Research Program supported the guideline development process, including performing systematic evidence reviews up to September 2017. The panel prioritized clinical questions and outcomes according to their importance for clinicians and patients. The panel used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach, including GRADE evidence-to-decision frameworks, to assess evidence and make recommendations, which were subject to public comment.

RESULTS

The panel agreed on 10 recommendations for screening, diagnosis, and management of cardiopulmonary and renal complications of SCD. Recommendations related to anticoagulation duration for adults with SCD and venous thromboembolism were also developed.

CONCLUSIONS

Most recommendations were conditional due to a paucity of direct, high-quality evidence for outcomes of interest. Future research was identified, including the need for prospective studies to better understand the natural history of cardiopulmonary and renal disease, their relationship to patient-important outcomes, and optimal management.

Gender-Related Differences in Sickle Cell Disease in a Pediatric Cohort: A Single-Center Retrospective Study

Sickle cell disease (SCD) is one of the most common monogenic disease worldwide. The incidence of SCD is not strictly gender-related as it is transmitted as an autosomal recessive disorder. In particular, the gender-related differences in pediatric SCD are not well-characterized. To address this matter, we retrospectively analyzed the clinical records of 39 pediatric patients with a diagnosis of SCD (hemoglobin SS genotype) focusing on gender differences analyzing various aspects of the disease and comprising both acute symptoms and late complications. We found various gender-related differences in our pediatric population. In particular, pain crisis frequency per year was significantly increased in the male population with a mean number of crisis per year of 1.6 vs. 0.6 in the female population (p = 0.04). Also, severe complications (both infectious and cardiovascular) were mostly found in the male population. SCD-related late cardiac complications were observed mainly in the male population (p = 0.04). Our data support the hypothesis that gender could play a role in determining the clinical course of SCD, even though further studies are needed to assess the exact weight of its influence over the course of the disease. The higher morbidity in males is a well-known feature of SCD in adults and these findings have been only partially studied in the pediatric population. These differences have, in adults, been attributed to hormonal variations found in the two sexes after puberty. In a pediatric population, other factors must be responsible for these discrepancies. These findings suggest that gender could be a valuable factor in the risk stratification of these patients at diagnosis, and possibly guide therapeutic decisions, with the final aim of personalizing the therapy.

Vascular Instability and Neurological Morbidity in Sickle Cell Disease: An Integrative Framework

It is well-established that patients with sickle cell disease (SCD) are at substantial risk of neurological complications, including overt and silent stroke, microstructural injury, and cognitive difficulties. Yet the underlying mechanisms remain poorly understood, partly because findings have largely been considered in isolation. Here, we review mechanistic pathways for which there is accumulating evidence and propose an integrative systems-biology framework for understanding neurological risk. Drawing upon work from other vascular beds in SCD, as well as the wider stroke literature, we propose that macro-circulatory hyper-perfusion, regions of relative micro-circulatory hypo-perfusion, and an exhaustion of cerebral reserve mechanisms, together lead to a state of cerebral vascular instability. We suggest that in this state, tissue oxygen supply is fragile and easily perturbed by changes in clinical condition, with the potential for stroke and/or microstructural injury if metabolic demand exceeds tissue oxygenation. This framework brings together recent developments in the field, highlights outstanding questions, and offers a first step toward a linking pathophysiological explanation of neurological risk that may help inform future screening and treatment strategies.

High incidence of venous thromboembolism recurrence in patients with sickle cell disease

Previous reports show increased incidence of venous thromboembolism [VTE, deep-vein thrombosis (DVT) and pulmonary embolus (PE)] in sickle cell disease (SCD) patients. The incidence, time course, and risk factors for VTE recurrence have been less well described. We determined the cumulative incidence of first VTE recurrence and bleeding in a cohort of SCD patients with incident VTE. Risk factors for recurrence and bleeding were also determined using multivariable Cox regression models, adjusting for gender, race/ethnicity, era of incident VTE, location and hospitalization-associated status of incident VTE, and SCD-related complications. Results are presented as adjusted hazard ratios (HR) and 95% confidence intervals (CI). Among 877 SCD patients with an incident VTE, the 1-year and 5-year cumulative incidence of recurrence was 13.2% (95% CI 11.0%-15.5%) and 24.1% (95% CI 21.2%-27.1%). Risk factors for VTE recurrence included more severe SCD (HR = 2.41; CI: 1.67-3.47), lower extremity DVT as the incident event (HR = 1.64; CI: 1.17-2.30), and pneumonia/acute chest syndrome (HR = 1.68; CI: 1.15-2.45). The cumulative incidence of bleeding was 4.9% (CI 3.5%-6.4%) at 6 months and 7.9% (CI: 6.2%-9.8%) at 1 year. More severe SCD (HR = 1.61; CI: 1.11-2.35) was associated with bleeding. The high incidence of VTE recurrence in patients with SCD suggests that extended anticoagulation may be indicated; however, this must be weighed against a relatively high risk of bleeding. Prospective, randomized studies of anticoagulation in SCD patients with VTE are needed.

Overcoming challenges of venous thromboembolism in sickle cell disease treatment

INTRODUCTION

Venous thromboembolism (VTE) is a common comorbid condition found in sickle cell disease (SCD) and is associated with increased mortality for adults with SCD. The pathophysiology that leads to the thrombophilic state in SCD has been previously reviewed; however, evidence-based guidelines to aid in diagnosis, prevention, and management of VTE are lacking. Areas covered: This review article will cover the pathophysiology underlying the hypercoagulable state, the epidemiology of VTE, and management strategies of VTE in SCD. Expert opinion: Providers should have a high suspicion for diagnosing VTE to help reduce morbidity and mortality in the SCD population. Unlike other thrombophilias, the risk of life-threatening anemia while being treated with anticoagulation is compounded with the potential complications surrounding red blood cell transfusions in this population (i.e. alloimmunization, hyperhemolysis) and this provides another complexity to managing VTE in this population. Clinical trials evaluating the risk and benefit of treatment and treatment duration are needed.

How I diagnose and treat venous thromboembolism in sickle cell disease

The incidence of venous thromboembolism (VTE) in adult patients with sickle cell disease (SCD) is high. However, overlapping features between the clinical presentation of VTE and SCD complications and a low index of suspicion for thrombosis can influence patient management decisions. VTE in SCD can therefore present management challenges to the clinical hematologist. Herein, we present 3 distinct clinical vignettes that are representative of our clinical practice with SCD patients. These vignettes are discussed with specific reference to the hypercoagulable state in SCD patients, recent VTE diagnosis and anticoagulant therapy guidelines from the general population, and evaluation of the risk of bleeding as a result of long-term exposure to anticoagulant therapy. We examine current diagnostic and treatment options, highlight limitations of the existing clinical prognostic models that offer personalized guidance regarding the duration of anticoagulation, and propose a clinical approach to guide the decision to extend anticoagulation beyond 3 months.