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

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

Sickle Cell Nephropathy: Current Understanding of the Presentation, Diagnostic and Therapeutic Challenges

Sickle cell nephopathy (SCN) begins early in childhood from failure of urinary concentration (hyposthenuria), albuminuria to hyperfiltration, hematuria and progression to falling glomerular filtration to end-stage renal disease and increased mortality. Renal involvement is more severe in homozygous individuals (HbSS) than in compound heterozygous patients (HbSC). The pathogenesis of SCN is multifactorial from hypoxia, acidosis, hemolysis, ischemia-reperfusion injury and albuminuria. The clinical manifestations depend on whether the main pathology is tubular, glomerular or a mixture of both abnormalities. This chapter offers a critical review of the recent literature and will highlight the pathophysiology, epidemiology, clinical manifestations and management of sickle cell nephropathy with particular focus on the major advance in the early diagnosis. Learning points: For SCN, the onset of hyperfiltration and albuminuria in infants and childhood is an opportunity to intervene early. There is no diagnostic markertest capable of detecting the onset of these changes. Moreover there is no reliable therapeutic agent to prevent or halt early changes due to SCN. The development of a marker of renal impairment in SCD such as such as Cystatin C assay if validated may be appropriate for wider clinical application

Delayed Hemolytic Transfusion Reaction in Sickle Cell Disease

Delayed hemolytic transfusion reactions (DHTR) are potentially life-threatening complications observed in patients with sickle cell disease. We review the clinical features, pathophysiology, laboratory evaluation, and management of this complication. It is important that DHTR be included in the differential diagnosis of acute pain episodes following a red blood cell transfusion in a patient with sickle cell disease

Care Seeking for Pain in Young Adults with Sickle Cell Disease

In individuals with sickle cell disease (SCD), recognizing the cues to an acute pain episode and responding appropriately are important. The purpose of this mixed-methods pilot study is to identify preliminary factors that influence care seeking for pain in young adults with SCD. Responses were received from 69 young adults with SCD, age 18-35 years. The majority of respondents (88%) wait until the pain intensity is an average of 8.7 (± 1.2) on a scale of 1 to 10 before seeking care. Prominent themes influencing care seeking for pain include: trying to treat pain at home, avoiding the emergency department because of past treatment experiences, the desire to avoid admission to the hospital, and the importance of time in the lives of the young adults with SCD. Young adults with SCD need additional support from family and healthcare providers in order to make timely, appropriate decisions regarding care seeking

The glomerulopathy of sickle cell disease

Sickle cell disease (SCD) produces many structural and functional abnormalities in the kidney, including glomerular abnormalities. Albuminuria is the most common manifestation of glomerular damage, with a prevalence between 26 and 68% in adult patients. The pathophysiology of albuminuria in SCD is likely multifactorial, with contributions from hyperfiltration, glomerular hypertension, ischemia-reperfusion injury, oxidative stress, decreased nitric oxide (NO) bioavailability, and endothelial dysfunction. Although its natural history in SCD remains inadequately defined, albuminuria is associated with increased echocardiography-derived tricuspid regurgitant jet velocity, systemic blood pressure, and hypertension, as well as history of stroke, suggesting a shared vasculopathic pathophysiology. While most patients with albuminuria are treated with angiotensin converting enzyme inhibitors/angiotensin receptor blockers, there are no published long-term data on the efficacy of these agents. With the improved patient survival following kidney transplantation, SCD patients with end-stage renal disease should be considered for this treatment modality. Given the high prevalence of albuminuria and its association with multiple SCD-related clinical complications, additional studies are needed to answer several clinically important questions in a bid to adequately elucidate its pathophysiology, natural history, and treatment

Hydroxyurea is associated with lower prevalence of albuminuria in adults with sickle cell disease

Albuminuria is an early manifestation of sickle cell nephropathy. Prior small case series suggests benefit of hydroxyurea in reducing albuminuria, with a similar trend noted in pediatric studies. We aimed to comprehensively evaluate hydroxyurea use and prevalence of albuminuria in adult sickle cell patients

Hemodynamic Characteristics and Predictors of Pulmonary Hypertension in Patients With Sickle Cell Disease

Pulmonary hypertension (PH) is a common comorbidity of sickle cell disease (SCD) with an associated increased mortality risk, but its etiology is not well-understood. To evaluate the hemodynamic characteristics, clinical predictors, and cardiovascular manifestations of elevated pulmonary arterial pressure in this population, we performed noninvasive hemodynamic assessments of 135 patients with SCD using Doppler echocardiography. A diagnosis of PH was based on gender-, age-, and body mass index (BMI)-specific normal reference ranges for tricuspid regurgitation jet velocities (TRV). A high TRV was noted in 34 (25%) of patients. Pulmonary vascular resistance (PVR) was elevated in only 2 of the 34 patients (6%) with suspected PH, but was significantly higher than in those with a normal TRV. In univariate regression, TRV correlated with age, BMI, left atrial pressure, and right ventricular stroke volume, and was negatively associated with hemoglobin and glomerular filtration rate. Left atrial pressure, right ventricular stroke volume, and hemoglobin remained independent predictors of TRV in a multivariate model. A higher TRV was also associated with larger right ventricular and right atrial chamber sizes and higher N-terminal pro-brain natriuretic peptide levels. Our results suggest that the mild elevation in TRV often observed in patients with SCD is rarely associated with a high PVR, and that multiple factors – including the compensatory high output state associated with anemia, pulmonary venous hypertension, and a pulmonary vasculopathy – may contribute to an elevated pulmonary arterial pressure in these patients

Risk factors for mortality in adult patients with sickle cell disease: a meta-analysis of studies in North America and Europe

Although recent studies show an improved survival of children with sickle cell disease in the US and Europe, for adult patients mortality remains high. This study was conducted to evaluate the factors associated with mortality in adult patients following the approval of hydroxyurea. We first evaluated the association between selected variables and mortality at an academic center (University of North Carolina). Data sources were then searched for publications from 1998 to June 2016, with meta-analysis of eligible studies conducted in North America and Europe to evaluate the associations of selected variables with mortality in adult patients. Nine studies, combined with the UNC cohort (total n=3257 patients) met the eligibility criteria. Mortality was significantly associated with age (per 10-year increase in age) [7 studies, 2306 participants; hazard ratio (HR): 1.28; 95% confidence interval (CI): 1.10–1.50], tricuspid regurgitant jet velocity 2.5 m/s or more (5 studies, 1577 participants; HR: 3.03; 95%CI: 2.0–4.60), reticulocyte count (3 studies, 1050 participants; HR: 1.05; 95%CI: 1.01–1.10), log(N-terminal-pro-brain natriuretic peptide) (3 studies, 800 participants; HR: 1.68; 95%CI: 1.48–1.90), and fetal hemoglobin (7 studies, 2477 participants; HR: 0.97; 95%CI: 0.94–1.0). This study identifies variables associated with mortality in adult patients with sickle cell disease in the hydroxyurea era

Decades after the cooperative study: A re-examination of systemic blood pressure in sickle cell disease

Previous studies report lower systemic blood pressures in patients with sickle cell disease (SCD) than in appropriate controls. The etiology of the lower systolic and diastolic blood pressures (SBP and DBP) remains uncertain. Blood pressure measurements from patients followed at our center (UNC cohort) were compared with values obtained from the Cooperative Study of Sickle Cell Disease (CSSCD) and healthy control subjects. Associations of SBP and DBP with clinical and laboratory covariates were performed in the UNC cohort. Patients in the UNC cohort were significantly older and had a higher BMI than those in the CSSCD (p <0.0001). There were no differences in the SBP and DBP between SCD patients in the UNC cohort and control subjects. In the SS/SD/Sβ0 thalassemia group, SBP was higher in the UNC cohort than in the CSSCD (p < 0.0001). On multivariate analysis, significant correlations were noted between SBP and age, BMI, history of hypertension and absolute neutrophil count. Compared with historic controls, SBP was significantly higher in our SCD patient cohort. There was no difference when blood pressure was compared between our patient cohort and control subjects. Age, BMI and neutrophil count may contribute to the modulation of SBP in SCD

Coagulation activation and inflammation in sickle cell disease-associated pulmonary hypertension

BACKGROUND: Pulmonary hypertension (PHT) is common in sickle cell disease (SCD). The purpose of this study was to determine whether markers of coagulation activation and inflammation are associated with PHT in SCD. DESIGN AND METHODS: This cross-sectional study was performed using a cohort of patients followed at an adult Sickle Cell Clinic. Pulmonary artery systolic pressure was determined by Doppler echocardiography, and the diagnosis of PHT was defined using age, sex and body mass index-adjusted reference ranges. Clinical laboratory examinations, including hematologic studies and biochemical tests, as well as various measures of coagulation activation, endothelial activation and inflammation, were conducted on SCD subjects and on healthy, race-matched control subjects without SCD. RESULTS: Patients with SCD (n=76) had higher plasma levels of markers of coagulation (thrombin-antithrombin complex, prothrombin fragment F1+2, D-dimer) and endothelial (soluble vascular endothelial cell adhesion molecule, sVCAM) activation compared with control subjects (n=6). SCD patients with PHT (n=26) had significantly higher levels of sVCAM compared with those patients without PHT (n=50). Although PHT patients showed increased plasma measures of coagulation activation, the differences were not statistically significant when compared to those of patients without PHT. HbSS patients with PHT also had a trend towards higher levels of other inflammatory cytokines (interleukins 6, 8 and 10) than HbSS patients without PHT. There was a modest negative correlation between hemoglobin and plasma measures of coagulation and endothelial activation, and modest positive correlations between markers of hemolysis and plasma measures of coagulation and endothelial activation. CONCLUSIONS: SCD patients with PHT have higher levels of markers of endothelial activation and other inflammatory markers than patients without PHT. A trend towards an increased level of markers of coagulation activation was observed in SCD patients with PHT compared with that in patients without PHT. Markers of hemolysis are associated with coagulation activation and endothelial dysfunction in SCD patients. Clinical trials of anticoagulants and anti-inflammatory agents are warranted in SCD patients with PHT