Payal Desai

Association of coagulation activation with clinical complications in sickle cell disease.

Background The contribution of hypercoagulability to the pathophysiology of sickle cell disease (SCD) remains poorly defined. We sought to evaluate the association of markers of coagulation and platelet activation with specific clinical complications and laboratory variables in patients with SCD. Design and Methods Plasma markers of coagulation activation (D-dimer and TAT), platelet activation (soluble CD40 ligand), microparticle-associated tissue factor (MPTF) procoagulant activity and other laboratory variables were obtained in a cohort of patients with SCD. Tricuspid regurgitant jet velocity was determined by Doppler echocardiography and the presence/history of clinical complications was ascertained at the time of evaluation, combined with a detailed review of the medical records. Results No significant differences in the levels of D-dimer, TAT, soluble CD40 ligand, and MPTF procoagulant activity were observed between patients in the SS/SD/Sβ0 thalassemia and SC/Sβ+ thalassemia groups. Both TAT and D-dimer were significantly correlated with measures of hemolysis (lactate dehydrogenase, indirect bilirubin and hemoglobin) and soluble vascular cell adhesion molecule-1. In patients in the SS/SD/Sβ0 thalassemia group, D-dimer was associated with a history of stroke (p = 0.049), TAT was associated with a history of retinopathy (p = 0.0176), and CD40 ligand was associated with the frequency of pain episodes (p = 0.039). In multivariate analyses, D-dimer was associated with reticulocyte count, lactate dehydrogenase, NT-proBNP and history of stroke; soluble CD40 ligand was associated with WBC count and platelet count; and MPTF procoagulant activity was associated with hemoglobin and history of acute chest syndrome. Conclusions This study supports the association of coagulation activation with hemolysis in SCD. The association of D-dimer with a history of stroke suggests that coagulation activation may contribute to the pathophysiology of stroke in clinically severe forms of SCD. More research is needed to evaluate the contribution of coagulation and platelet activation to clinical complications in SCD.

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

BACKGROUND 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. METHODS We performed a cross-sectional study of 149 adult patients followed between 2000 and 2011 in a comprehensive sickle cell clinic. All patients were assessed for albuminuria either by direct measurement or by urinary chemical strip (dipstick) testing. Urinary albumin-to-creatinine ratios (UACRs) were available for 112 patients. Hydroxyurea exposure was defined as ≥3 months of therapy before the assessment of albuminuria. Albuminuria was defined as either UACR ≥30 mg/g or ≥1+ proteinuria on two separate dipsticks. We constructed a multivariate logistic regression model to assess the association between hydroxyurea and albuminuria. RESULTS The prevalence of albuminuria was lower among patients on hydroxyurea (34.7 versus 55.4%; P = 0.01) as was median albumin excretion (17.9 versus 40.5 mg/g; P = 0.04). In multivariate analysis, hydroxyurea was associated with a lower likelihood of albuminuria (odds ratio 0.28, 95% CI: 0.11-0.75, P = 0.01), adjusting for age, angiotensin-converting enzyme inhibitor/angiotensin receptor blocker use, tricuspid regurgitant jet velocity, hypertension and acute chest syndrome. CONCLUSIONS In our population of sickle cell patients, those using hydroxyurea were less than one-third as likely to exhibit albuminuria. Hydroxyurea use may prevent development of overt nephropathy or the progression of sickle cell disease nephropathy to end-stage renal disease, and its use for this indication merits further investigation.

A Pilot Study of Eptifibatide for Treatment of Acute Pain Episodes in Sickle Cell Disease

INTRODUCTION The contribution of platelet activation to the pathogenesis of sickle cell disease (SCD) remains uncertain. We evaluated the safety and efficacy of eptifibatide, a synthetic peptide inhibitor of the αIIbβ3 receptor, in SCD patients during acute painful episodes. MATERIALS AND METHODS In this single site, double-blind, placebo-controlled trial, eligible patients with SCD admitted for acute painful episodes were randomized to receive eptifibatide or placebo at a ratio of 2:1. RESULTS Thirteen patients (SS - 10, Sβ(0) - 2, SC - 1) were randomized to receive either eptifibatide (N=9; 6 females; median age - 25years) or placebo (N=4; 3 females; median age - 31years). In the intent-to-treat analysis, there were no major bleeding episodes in either the eptifibatide or placebo arms (point estimate of difference: 0.00, 95% CI; -0.604, 0.372). There was one minor bleeding episode in the eptifibatide arm (point estimate of difference for any bleeding: 0.11, 95% CI: -0.502, 0.494). There was no significant difference in the proportion of patients with thrombocytopenia between the treatment groups (point estimate of difference: 0.11, 95% CI: -0.587, 0.495). There were no differences in the median times to discharge, median times to crisis resolution or the median total opioid use. CONCLUSIONS In this small study, eptifibatide appeared to be safe, but did not improve the times to crisis resolution or hospital discharge. Adequately powered studies are required to evaluate the safety and efficacy of eptifibatide in SCD. Clinicaltrials.gov Identifier: NCT00834899.

Alloimmunization is associated with older age of transfused red blood cells in sickle cell disease.

Red blood cell (RBC) alloimmunization is a significant clinical complication of sickle cell disease (SCD). It can lead to difficulty with cross‐matching for future transfusions and may sometimes trigger life‐threatening delayed hemolytic transfusion reactions. We conducted a retrospective study to explore the association of clinical complications and age of RBC with alloimmunization in patients with SCD followed at a single institution from 2005 to 2012. One hundred and sixty six patients with a total of 488 RBC transfusions were evaluated. Nineteen patients (11%) developed new alloantibodies following blood transfusions during the period of review. The median age of RBC units was 20 days (interquartile range: 14–27 days). RBC antibody formation was significantly associated with the age of RBC units (P = 0.002), with a hazard ratio of 3.5 (95% CI: 1.71–7.11) for a RBC unit that was 7 days old and 9.8 (95% CI: 2.66–35.97) for a unit that was 35 days old, 28 days after the blood transfusion. No association was observed between RBC alloimmunization and acute vaso‐occlusive complications. Although increased echocardiography‐derived tricuspid regurgitant jet velocity (TRV) was associated with the presence of RBC alloantibodies (P = 0.02), TRV was not significantly associated with alloimmunization when adjusted for patient age and number of transfused RBC units. Our study suggests that RBC antibody formation is significantly associated with older age of RBCs at the time of transfusion. Prospective studies in patients with SCD are required to confirm this finding. Am. J. Hematol. 90:691–695, 2015.

Association of soluble fms-like tyrosine kinase-1 with pulmonary hypertension and haemolysis in sickle cell disease

The pathophysiology of pulmonary hypertension (PHT) in sickle cell disease (SCD) is probably multifactorial. Soluble fms‐like tyrosine kinase‐1 (sFLT‐1) is a member of the vascular endothelial growth factor receptor (VEGFR) family. By adhering to and inhibiting VEGF and placenta growth factor, it induces endothelial dysfunction. We sought to evaluate the association of sFLT‐1 with clinical complications of SCD. We confirmed that sFLT‐1 was significantly elevated in SCD patients compared to healthy, race‐matched control subjects. The level of sFLT‐1 was significantly higher in patients with PHT, but no association was observed between sFLT‐1 and the frequency of acute pain episodes or history of acute chest syndrome. sFLT‐1 was correlated with various measures of haemolysis, erythropoietin and soluble vascular cell adhesion molecule‐1. By inducing endothelial dysfunction, sFLT‐1 may contribute to the pathogenesis of SCD‐associated PHT, although this effect does not appear to be independent of haemolysis.

The acute chest syndrome of sickle cell disease

Introduction: Acute chest syndrome (ACS), a leading cause of morbidity and mortality in sickle cell disease (SCD), is an acute illness characterized by fever and/or respiratory symptoms, accompanied by a new pulmonary infiltrate on a chest X-ray. There is increasing knowledge regarding the etiology and pathogenesis of ACS in SCD. A high index of suspicion is required for the diagnosis of ACS. Treatment of ACS involves the judicious use of intravenous fluids and analgesics, aggressive incentive spirometer and pulmonary toileting, antibiotics and transfusion therapy. Areas covered: This review evaluates the epidemiology, clinical and laboratory presentation, etiology and pathogenesis of ACS. It also reviews the standard treatments as well as experimental treatments in ACS. Expert opinion: Despite an increased understanding of its etiology and pathogenesis, ACS remains a leading cause of morbidity and mortality in SCD. In patients admitted with a painful crisis, there is need for a high index of suspicion, as pain episodes may be a prodrome for the development of ACS. Patients with a diagnosis of ACS should be aggressively managed to prevent clinical deterioration. Clinical trials using novel drugs for the treatment of ACS are greatly warranted.

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

Multiple studies have reported that patients with SCD have lower systemic blood pressures when compared with age-, sex-, and race-matched controls (1–4). This was confirmed by the Cooperative Study of Sickle Cell Disease (CSSCD), a natural history study of SCD in the United States (4). With the recent advances in the care of patients with SCD, we compared systolic and diastolic blood pressure (SBP and DBP) measurements in a patient cohort followed at our clinical center with values obtained in the CSSCD and from healthy, control subjects. Furthermore, we evaluated the association of SBP and DBP with clinical and laboratory variables in our patient cohort. Blood pressure measurements were obtained in 156 SCD patients in the UNC cohort and 1232 patients in the CSSCD cohort. Patients in the UNC cohort were older and had a higher BMI than patients in the CSSCD cohort (Table 1). The UNC cohort also had a significantly higher proportion of patients with a diagnosis of hypertension and patients on antihypertensive medications. Table 1 Baseline Clinical and Laboratory Characteristics of Study Subjects Patients in the UNC and CSSCD cohorts were categorized into 2 groups based on presumed disease severity - SS/SD/Sβ0 thalassemia and SC/Sβ+ thalassemia, without consideration of alpha and delta thalassemia status. There were 129 patients in the SS/SD/Sβ0 thalassemia group (83%) and 27 patients in the SC/Sβ+ thalassemia group (17%) in the UNC cohort, with 899 patients in the SS/SD/Sβ0 thalassemia group (73%) and 333 patients in the SC/Sβ+ thalassemia group (27%) in the CSSCD cohort. The SBP in the SS/SD/Sβ0 thalassemia group was significantly higher in the UNC cohort than in the CSSCD cohort (122 ± 15 mm Hg vs. 113 ± 14.5 mm Hg, p < 0.0001), but there was no difference in the DBP when both cohorts were compared (69 ± 10.5 mm Hg vs. 69 ± 10.5 mm Hg; p = 0.8). Similarly, in the SC/Sβ+ thalassemia group, the SBP was significantly higher in the UNC cohort (131 ±12 mm Hg vs. 116 ±15.5 mm Hg; p < 0.0001), but no difference was observed when the DBP in both cohorts were compared. When all the SCD patients were stratified by age, the SBP in the UNC cohort was higher in male patients in the 35 – 44-year age group and female patients in the 18 – 24-year, 25 – 34-year and 35 – 44-year age groups compared with the CSSCD cohort (supplementary data, Figure 1; Table 1). We compared the SBP and DBP in SCD patients in the UNC cohort with values from 24 healthy, African-American control subjects without SCD (genotype- AA; median age: 37 years [IQR: 26, 49 years]; BMI: 30.5 [IQR: 25.6, 36.7]). No significant differences were observed in the SBP or DBP when both groups were compared. Furthermore, there were no significant differences in the SBP and DBP when patients in the SS/SD/Sβ0 group were compared with healthy controls. However, patients in the SC/Sβ+ group had significantly higher SBP when compared with healthy controls (130.9 ± 12.1 mm Hg vs. 120.9 ± 11.3 mm Hg, p = 0.01), although no difference was observed in the DBP when both groups were compared. Significant correlations were observed between SBP and age (ρ = 0.37, p < 0.0001) and BMI (ρ = 0.41, p < 0.0001) (Table 2). Patients with a history of hypertension as well as those on antihypertensive therapy had significantly higher SBP than those without such history or therapy. Modest correlations were observed between SBP and white blood cell count, hemoglobin, reticulocyte count, lactate dehydrogenase, total bilirubin, indirect bilirubin, and placenta growth factor (PIGF) (Table 3). There were significant correlations between DBP and age and BMI. Modest correlations were also observed between DBP and hemoglobin, platelet count, reticulocyte count, total bilirubin, and indirect bilirubin. There were no significant associations between the evaluated SCD-related clinical complications and either SBP or DBP. Table 2 Association of Systolic and Diastolic Blood Pressure with Clinical Variables in UNC Cohort Table 3 Association of Systolic andDiastolic Blood Pressure with Laboratory Variables in UNC Cohort After controlling for other covariates, SBP was significantly associated with age (estimate: 0.30, p = 0.0026), BMI (estimate: 0.76, p < 0.0001), prior diagnosis of hypertension (estimate: 6.48, p = 0.027), absolute neutrophil count (estimate: −1.18, p = 0.023), but not with lactate dehydrogenase (estimate: 0.0017, p = 0.49) or hemoglobin (estimate: 1.01, p = 0.14). This means that we expect an increase in SBP by 0.30 mm Hg for every 1 year increase in age; an increase in SBP by 0.76 mm Hg for every 1 kg/m2 increase in BMI; and a decrease in SBP by 1.18 mm Hg for every 1 × 109/L increase in absolute neutrophil count. For a binary response such as prior diagnosis of hypertension, the estimated value of 6.48 indicates that having a history of hypertension is predicted to result in an increase in SBP of 6.48 mm Hg compared to no history of hypertension. Similarly, after controlling for other covariates, DBP was significantly associated with age (estimate: 0.25, p = 0.0004), hemoglobin (estimate: 1.71, p = 0.0021), history of smoking (estimate: −4.96, p = 0.0074), but not with lactate dehydrogenase (estimate: −0.00096, p = 0.62). Despite reported lower systemic blood pressures, patients with higher SBP relative to the SCD population appear to be at higher risk for stroke (4, 5), echocardiography-defined pulmonary hypertension (6), albuminuria (7, 8), and increased mortality (4). Given the risk of clinical complications despite the apparent lower blood pressures than those obtained in control populations, it is uncertain whether the usual recommendations for the diagnosis of hypertension apply to patients with SCD. We found a significantly higher SBP in SCD patients followed at our center than was observed in the CSSCD. Furthermore, there were no significant differences when the SBP and DBP in SCD patients followed at our center were compared with healthy, control subjects. This finding is similar to that by Thompson and colleagues which showed no difference in the SBP between a cohort of SCD patients and healthy controls in Jamaica (8). Consistent with a previous report (4), we found an association between SBP and both age and BMI. While patients in the UNC cohort were significantly older than those in the CSSCD, SBP and DBP values in the UNC cohort were higher when specific age groups were compared, suggesting that age is not the primary reason for the blood pressure differences in both patient cohorts. With the known association between weight and systemic blood pressure (9), the higher BMI in the UNC cohort may contribute to their higher blood pressure values compared to patients in the CSSCD. Although it has been suggested that lower systemic blood pressures in SCD may be a result of higher urinary sodium loss due to hyposthenuria (3, 4), intravenous salt loading had no effect on blood pressure (10). Furthermore, individuals with sickle cell trait, who also exhibit hyposthenuria, do not have lower blood pressures than age- and race-matched controls (11). There are conflicting reports on the association of anemia with systemic blood pressure in SCD (3, 4, 12). We observed modest associations between markers of hemolysis and both SBP and DBP on univariate analysis, but only hemoglobin remained significantly associated with DBP on multivariate analysis, suggesting that hemolysis may not play a substantial role in blood pressure modulation in SCD. The inverse correlation between SBP and PlGF on univariate analysis suggests that PlGF may play a role in the regulation of blood pressure in SCD. This angiogenic growth factor is higher in SCD patients than in control subjects (13). As in preeclampsia (14), PlGF may contribute to the modulation of systemic blood pressure in SCD. Depletion of neutrophils in healthy mice reduces SBP and produces an impairment of vascular constriction studied ex vivo (15). This effect was attributed to neutrophil suppression of interferon-mediated inducible nitric oxide synthase expression. The reason for the contradictory finding in SCD patients in our study is uncertain. SCD is referred to as a chronic inflammatory state (16) and patients exhibit elevated leukocyte counts and abnormal activation of various cellular elements (17) even in the non-crisis, “steady state”. Leukocytosis is also a risk factor for multiple complications, including acute chest syndrome (18) hemorrhagic stroke (5), vasoocclusive crises (19) and increased mortality (20). Our study suggests that the inflammatory state, by possibly increasing the rate of complications and disease severity, may produce lower blood pressures in patients with SCD. This study was not primarily designed to evaluate systemic blood pressure in SCD. Blood pressure measurement was performed using different techniques in our patient cohort and the CSSCD. Our patients were recruited from a specialty clinic at a tertiary care medical center, and may not represent all patients with SCD. As with all cross-sectional studies, this analysis demonstrates associations, but cannot prove causation. In conclusion, patients with SCD in our cohort have significantly higher systemic blood pressures compared with a historical cohort. The blood pressures of our patient cohort are not significantly different when compared with control subjects. SBP is associated with age, BMI, history of hypertension and inversely associated with absolute neutrophil count.

Association between diffuse myocardial fibrosis and diastolic dysfunction in sickle cell anemia.

Sickle cell anemia (SCA)-related cardiomyopathy is characterized by diastolic dysfunction and hyperdynamic features. Diastolic dysfunction portends early mortality in SCA. Diastolic dysfunction is associated with microscopic myocardial fibrosis in SCA mice, but the cause of diastolic dysfunction in humans with SCA is unknown. We used cardiac magnetic resonance measurements of extracellular volume fraction (ECV) to discover and quantify diffuse myocardial fibrosis in 25 individuals with SCA (mean age, 23 ± 13 years) and determine the association between diffuse myocardial fibrosis and diastolic dysfunction. ECV was calculated from pre- and post-gadolinium T1 measurements of blood and myocardium, and diastolic function was assessed by echocardiography. ECV was markedly increased in all participants compared with controls (0.44 ± 0.08 vs 0.26 ± 0.02, P < .0001), indicating the presence of diffuse myocardial fibrosis. Seventeen patients (71%) had diastolic abnormalities, and 7 patients (29%) met the definition of diastolic dysfunction. Participants with diastolic dysfunction had higher ECV (0.49 ± 0.07 vs 0.37 ± 0.04, P = .01) and N-terminal pro-brain natriuretic peptide (NT-proBNP; 191 ± 261 vs 33 ± 33 pg/mL, P = .04) but lower hemoglobin (8.4 ± 0.3 vs 10.9 ± 1.4 g/dL, P = .004) compared with participants with normal diastolic function. Participants with the highest ECV values (≥0.40) were more likely to have diastolic dysfunction (P = .003) and increased left atrial volume (57 ± 11 vs 46 ± 12 mL/m2, P = .04) compared with those with ECV <0.4. ECV correlated with hemoglobin (r = -0.46, P = .03) and NT-proBNP (r = 0.62, P = .001). In conclusion, diffuse myocardial fibrosis, determined by ECV, is a common and previously underappreciated feature of SCA that is associated with diastolic dysfunction, anemia, and high NT-proBNP. Diffuse myocardial fibrosis is a novel mechanism that appears to underlie diastolic dysfunction in SCA.

Longitudinal study of echocardiography-derived tricuspid regurgitant jet velocity in sickle cell disease

Although echocardiography‐derived tricuspid regurgitant jet velocity (TRV) is associated with increased mortality in sickle cell disease (SCD), its rate of increase and predictive markers of its progression are unknown. We evaluated 55 subjects (median age: 38 years, range: 20–65 years) with at least two measurable TRVs, followed for a median of 4·5 years (range: 1·0–10·5 years) in a single‐centre, prospective study. Thirty‐one subjects (56%) showed an increase in TRV, while 24 subjects (44%) showed no change or a decrease in TRV. A linear mixed effects model indicated an overall rate of increase in the TRV of 0·02 m/s per year (P = 0·023). The model showed that treatment with hydroxycarbamide was associated with an initial TRV that was 0·20 m/s lower than no such treatment (P = 0·033), while treatment with angiotensin converting enzyme inhibitors and angiotensin receptor blockers was associated with an increase in the TRV (P = 0·006). In summary, although some patients have clinically meaningful increases, the overall rate of TRV increase is slow. Treatment with hydroxycarbamide may decrease the progression of TRV. Additional studies are required to determine the optimal frequency of screening echocardiography and the effect of therapeutic interventions on the progression of TRV in SCD.