Plasma Concentration of Platelet-Derived Microparticles Is Related to Painful Vaso-Occlusive Phenotype Severity in Sickle Cell Anemia

High plasma level of microparticles (MPs) deriving mainly from erythrocytes and platelets has been detected in sickle cell anemia (SCA) patients. Flow cytometry was used to determine the concentration of MPs in two groups of SCA patients exhibiting marked differences in painful vaso-occlusive crisis rates [a non-severe group (n = 17) and a severe group (n = 12)], and in a control group composed of healthy subjects (n = 20). A 3- to 4-fold increase of total MP plasma concentration was detected in SCA patients. Higher platelet-derived MPs concentration was detected in the severe SCA group while erythrocyte-derived MPs concentration was increased in the non-severe SCA patient group only. Our results suggest that plasma concentration of MPs shed by platelets is a biomarker of the vaso-occlusive phenotype-related severity.     

A Family Study of IgG Subclasses in Sickle Cell Anemia

Three siblings with sickle cell anemia were studied immunologically and hematologically. Their patterns of Protein A-Sepharose chromatography distribution showed considerable heterogeneity, particularly with respect to the IgG2 and IgG3 subclasses, even though their hematological make up was similar. An attempt was made to correlate their IgG2: IgG1 subclass ratios with their clinical history of recurrent bacterial infections, as well as a possible compensatory IgG3 heterogeneity.     

Genome Wide Association Study of Fetal Hemoglobin in Sickle Cell Anemia in Tanzania

Background

Fetal hemoglobin (HbF) is an important modulator of sickle cell disease (SCD). HbF has previously been shown to be affected by variants at three loci on chromosomes 2, 6 and 11, but it is likely that additional loci remain to be discovered.

Methods and Findings

We conducted a genome-wide association study (GWAS) in 1,213 SCA (HbSS/HbSβ⁰) patients in Tanzania. Genotyping was done with Illumina Omni2.5 array and imputation using 1000 Genomes Phase I release data. Association with HbF was analysed using a linear mixed model to control for complex population structure within our study. We successfully replicated known associations for HbF near BCL11A and the HBS1L-MYB intergenic polymorphisms (HMIP), including multiple independent effects near BCL11A, consistent with previous reports. We observed eight additional associations with P<10⁻⁶. These associations could not be replicated in a SCA population in the UK.

Conclusions

This is the largest GWAS study in SCA in Africa. We have confirmed known associations and identified new genetic associations with HbF that require further replication in SCA populations in Africa.     

Outcomes of Acute Chest Syndrome in Adult Patients with Sickle Cell Disease: Predictors of Mortality

Adults with sickle cell disease(SCD) are a growing population. Recent national estimates of outcomes in acute chest syndrome(ACS) among adults with SCD are lacking. We describe the incidence, outcomes and predictors of mortality in ACS in adults. We hypothesize that any need for mechanical ventilation is an independent predictor of mortality.

Methods

We performed a retrospective analysis of the Nationwide Inpatient Sample(2004–2010),the largest all payer inpatient database in United States, to estimate the incidence and outcomes of ACS needing mechanical ventilation(MV) and exchange transfusion(ET) in patients >21 years. The effects of MV and ET on outcomes including length of stay(LOS) and in-hospital mortality(IHM) were examined using multivariable linear and logistic regression models respectively. The effects of age, sex, race, type of sickle cell crisis, race, co-morbid burden, insurance status, type of admission, and hospital characteristics were adjusted in the regression models.

Results

Of the 24,699 hospitalizations, 4.6% needed MV(2.7% for <96 hours, 1.9% for ≥96 hours), 6% had ET, with a mean length of stay(LOS) of 7.8 days and an in-hospital mortality rate(IHM) of 1.6%. There was a gradual yearly increase in ACS hospitalizations that needed MV(2.6% in 2004 to 5.8% in 2010). Hb-SS disease was the phenotype in 84.3% of all hospitalizations. After adjusting for a multitude of patient and hospital related factors, patients who had MV for <96 hours(OR = 67.53,p<0.01) or those who had MV for ≥96 hours(OR = 8.73,p<0.01) were associated with a significantly higher odds for IHM when compared to their counterparts. Patients who had MV for ≥96 hours and those who had ET had a significantly longer LOS in-hospitals(p<0.001).

Conclusion

In this large cohort of hospitalized adults with SCD patients with ACS, the need for mechanical ventilation predicted higher mortality rates and increased hospital resource utilization. Identification of risk factors may enable optimization of outcomes.     

Validation of a Low-Cost Paper-Based Screening Test for Sickle Cell Anemia

Background

The high childhood mortality and life-long complications associated with sickle cell anemia (SCA) in developing countries could be significantly reduced with effective prophylaxis and education if SCA is diagnosed early in life. However, conventional laboratory methods used for diagnosing SCA remain prohibitively expensive and impractical in this setting. This study describes the clinical validation of a low-cost paper-based test for SCA that can accurately identify sickle trait carriers (HbAS) and individuals with SCA (HbSS) among adults and children over 1 year of age.

Methods and Findings

In a population of healthy volunteers and SCA patients in the United States (n = 55) the test identified individuals whose blood contained any HbS (HbAS and HbSS) with 100% sensitivity and 100% specificity for both visual evaluation and automated analysis, and detected SCA (HbSS) with 93% sensitivity and 94% specificity for visual evaluation and 100% sensitivity and 97% specificity for automated analysis. In a population of post-partum women (with a previously unknown SCA status) at a primary obstetric hospital in Cabinda, Angola (n = 226) the test identified sickle cell trait carriers with 94% sensitivity and 97% specificity using visual evaluation (none of the women had SCA). Notably, our test permits instrument- and electricity-free visual diagnostics, requires minimal training to be performed, can be completed within 30 minutes, and costs about $0.07 in test-specific consumable materials.

Conclusions

Our results validate the paper-based SCA test as a useful low-cost tool for screening adults and children for sickle trait and disease and demonstrate its practicality in resource-limited clinical settings.     

Mortality in Adult Offspring of Immigrants: A Swedish National Cohort Study

BackgroundHigher risks of psychiatric disorders and lower-than-average subjective health in adulthood have been demonstrated in offspring of immigrants in Sweden compared with offspring of native Swedes, and linked to relative socioeconomic disadvantage. The present study investigated mortality rates in relation to this inequity from a gender perspective.MethodsWe used data from national registers covering the entire Swedish population aged 18-65 years. Offspring of foreign-born parents who were either Swedish born or had received residency in Sweden before school age (<7 years) were defined as “offspring of immigrants.” We used Cox regression models to examine the association between parental country of birth and mortality between 1990 and 2008, with adjustment for education, income, age and family type.ResultsMale offspring of immigrants from the Middle East (HR:2.00, CI:1.66-2.26), other non-European countries (HR:1.80, CI:1.36-2.36) and Finland (HR:1.56, CI:1.48-1.65) showed an age-adjusted excess mortality risk from all causes of death when compared to offspring with Swedish-born parents. Income, but not education, greatly attenuated these increased mortality risks. No excess mortality rates were found among female offspring of immigrants, with the exception of external cause of death among offspring of Finnish immigrants.ConclusionThe study demonstrates high mortality rates in male offspring of immigrants from Finland and non-European countries that are associated with economic, but not educational, disadvantage. No increased mortality rates were found among female offspring of immigrants. Future studies are needed to explain this gender differential and why income, but not education, predicts mortality in male offspring of immigrants.     

Serum Copeptin and Cortisol Do Not Accurately Predict Sickle Cell Anaemia Vaso-Occlusive Crisis as C-Reactive Protein

Objective

This study assessed the diagnostic performance and prognostic properties of C-reactive protein (CRP), copeptin and cortisol in individuals with sickle cell anaemia (SCA).

Design

Prospective case-control study

Methods

Sixty consecutive SCA subjects (18–40 years) comprising 30 subjects in the steady state and 30 subjects in vaso-occlusive crisis (VOC) were recruited into this study. Thirty (30) apparently healthy individuals with HbAA genotype served as controls. ELISA was used for the determination of serum levels of copeptin, CRP and cortisol. Data obtained were statistically analyzed using the Student’s t-test and Mann Whitney U as appropriate and P<0.05 was considered significant.

Results

SCA subjects in VOC had significantly lower copeptin level and significantly higher CRP level compared with controls. However, serum levels of copeptin, cortisol and CRP were significantly higher in SCA subjects in VOC compared with SCA subjects in steady state. Furthermore, CRP had the widest Area under the ROC curve (AUROC) than copeptin and cortisol. No significant difference was observed in the levels of copeptin, CRP and cortisol when SCA subjects in VOC who were hospitalized for less ≤5 days were compared with subjects who had longer stays.

Conclusion

It could be concluded that C-reactive protein has a superior diagnostic performance for vaso-occlusive crisis in individuals with sickle cell anaemia and that C-reactive protein, cortisol and copeptin are not good prognostic markers in SCA subjects in vaso-occlusive crisis.     

Phase 1 Study of the E-Selectin Inhibitor GMI 1070 in Patients with Sickle Cell Anemia

Background

Sickle cell anemia is an inherited disorder of hemoglobin that leads to a variety of acute and chronic complications. Abnormal cellular adhesion, mediated in part by selectins, has been implicated in the pathophysiology of the vaso-occlusion seen in sickle cell anemia, and selectin inhibition was able to restore blood flow in a mouse model of sickle cell disease.

Methods

We performed a Phase 1 study of the selectin inhibitor GMI 1070 in patients with sickle cell anemia. Fifteen patients who were clinically stable received GMI 1070 in two infusions.

Results

The drug was well tolerated without significant adverse events. There was a modest increase in total peripheral white blood cell count without clinical symptoms. Plasma concentrations were well-described by a two-compartment model with an elimination T_1/2 of 7.7 hours and CLr of 19.6 mL/hour/kg. Computer-assisted intravital microscopy showed transient increases in red blood cell velocity in 3 of the 4 patients studied.

Conclusions

GMI 1070 was safe in stable patients with sickle cell anemia, and there was suggestion of increased blood flow in a subset of patients. At some time points between 4 and 48 hours after treatment with GMI 1070, there were significant decreases in biomarkers of endothelial activation (sE-selectin, sP-selectin, sICAM), leukocyte activation (MAC-1, LFA-1, PM aggregates) and the coagulation cascade (tissue factor, thrombin-antithrombin complexes). Development of GMI 1070 for the treatment of acute vaso-occlusive crisis is ongoing.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00911495","term_id":"NCT00911495"}}NCT00911495     

Red Blood Cell and Serum Magnesium Levels Among Children and Adolescents With Sickle Cell Anemia

This study investigated neurotoxicity of chronic fluorosis in the rat hippocampus. Newly weaning, male, Sprague-Dawley (SD) rats were administered 15, 30, and 60 mg/L sodium fluoride (NaF) solution (fluorine ion concentration 8.25, 16.50, and 33.00 mg/L, respectively), and tap water, for 18 months. The neurotoxicological mechanism was examined with a focus on intracellular calcium overload. Results showed that as the fluoride concentration increased, calcium ion concentration [Ca²⁺], the expression of calcium/calmodulin-dependent protein kinase II α (CaMKIIα), and the expression of catus proto-oncogene protein c-fos (c-fos) all tend to increase. Compared to the control group, Ca²⁺, CaMKIIα, and c-fos significantly increased (P < 0.05) in the moderate-fluoride and the high-fluoride groups. These results indicate that Ca²⁺/CaMKIIα/c-fos channel signal may be the molecular mechanism of central nervous system damage caused by chronic fluoride intoxication. Moreover, elevated Ca²⁺ concentration in the hippocampus may be the initiating factor of neuronal apoptosis induced by fluoride.     

Risk Factors of Pulmonary Hypertension in Brazilian Patients with Sickle Cell Anemia

This study was a prospective cross-sectional cohort study of 125 patients with sickle cell anemia (SS) between the ages of 16 to 60 years. Enrolled patients were followed-up prospectively for 15 months. Demographic, clinical, hematological and routine biochemical data were obtained on all patients. Six-minute walk test and Doppler Echocardiography were performed on all patients. A tricuspid regurgitant jet velocity (TRJV) < 2.5 m/sec was considered normal, 2.5 ≤ TRJV ≤ 3.0 was considered mild-moderate and > 3.0 m/sec, severe. Patients with abnormal TRJV were significantly older and more anemic, had significantly higher lactate dehydrogenase (LDH) levels, reticulocyte count and incidence of death. The logistic multimodal model implemented for the 125 patients indicated that age was the covariate that influenced the outcome of normal or abnormal TRJV with a cutoff age of thirty-two years. The survival rate for the group of patients with creatinine (Cr) > 1.0 mg/dL was lower than the group with Cr ≤ 1 and normal TRJV. A coefficient matrix showed that the LDH values were weakly correlated with the reticulocyte count but strongly correlated with hemoglobin suggesting that the TRJV values were not correlated with the hemolytic rate but with anemia. Ten patients died during the follow-up of whom 7 had TRJV > 2.5 m/sec. Acute chest syndrome was the most common cause of death followed by sepsis. In conclusion, this study shows that patients with SS older than thirty-two years with high LDH, elevated TRJV, severe anemia and Cr > 1 have poor prognosis and may be at risk of having pulmonary hypertension and should undergo RHC.     

In the Blood: Sickle Cell Anemia and the Politics of Race

In the Blood: Sickle Cell Anemia and the Politics of Race. Melbourne Tapper. Philadelphia: University of Pennsylvania Press, 1999.viii. 163pp.     

Anemia and Dental Caries in Pregnant Women: a Prospective Cohort Study

The objective was to evaluate the effect of anemia during pregnancy on the risk of dental caries development in pregnant women. A prospective cohort including a sample of pregnant women in a prenatal care unit of São Luís, Brazil, was done. The incidence of dental caries during pregnancy, according to Nyvad’s criteria, was the outcome. The main independent variables were serum iron, ferritin, hemoglobin, erythrocyte, hematocrit, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and red cell distribution width (RDW). Pregnant women (n = 121) were evaluated at two moments: up to 16th week of gestational age (T1) and in the last trimester of pregnancy (T2). Crude and adjusted associations were estimated by the incidence ratio risk (IRR) and respective 95% confidence intervals (95%CI). After adjustment, higher serum concentrations of ferritin (IRR = 0.97, 95%CI 0.95–0.99) in T1, and Fe (IRR = 0.99, 95%CI 0.98–0.99), ferritin (IRR = 0.99, 95%CI 0.98–0.99), erythrocyte (IRR = 0.71, 95%CI 0.50–0.99), hemoglobin (IRR = 0.84, 95%CI 0.73–0.96), hematocrit (IRR = 0.93, 95%CI 0.88–0.98), MCV (IRR = 0.91, 95%CI 0.86–0.96), and MCH (IRR = 0.83, 95%CI 0.74–0.93) in T2, were associated with fewer incidence of dental caries in pregnant women. Iron deficiency anemia during pregnancy is a risk factor for the incidence of dental caries in these women.     

Severe Nocturnal and Postexercise Hypoxia in Children and Adolescents with Sickle Cell Disease

Hypoxia is a common feature in children with sickle cell disease (SCD) that is inconsistently associated with painful crises and acute chest syndrome. To assess the prevalence and risk factors of hypoxia, we recorded daytime, nocturnal, and postexercise pulse oximetry (SpO₂) values in 39 SCD patients with a median age of 10.8 years. Median daytime SpO₂ was 97% (range, 89%–100%), and 36% of patients had daytime hypoxia defined as SpO₂<96%. Median nocturnal SpO₂ was 94.7% (range, 87.7%–99.5%), 50% of patients had nocturnal hypoxia defined as SpO₂≤93%, and 11(37%) patients spent more than 10% of their total sleep time with SpO₂<90%. Median postexercise SpO₂ was 94% (range, 72%–100%) and 44.7% of patients had postexercise hypoxia defined as an SpO₂ decrease ≥3% after a 6-minute walk test. Among patients with normal daytime SpO₂, 35% had nocturnal and 42% postexercise hypoxia. Compared to 9 patients without daytime, nocturnal, or postexercise hypoxia, 25 patients with hypoxia under at least one of these three conditions had greater anemia severity (P = 0.01), lower HbF levels (P = 0.04), and higher aspartate aminotransferase levels (P = 0.03). Males predominated among patients with postexercise hypoxia (P = 0.004). Hypoxia correlated neither with painful crises nor with acute chest syndrome. Of 32 evaluable patients, 6 (18.8%) had a tricuspid regurgitation velocity ≥2.6 m/s, and this feature was associated with anemia (P = 0.044). Median percentage of the predicted distance covered during a 6-minute walk test was 86% [46–120]; the distance was negatively associated with LDH (P = 0.044) and with a past history of acute chest syndrome (P = 0.009). In conclusion, severe episodes of nocturnal and postexercise hypoxia are common in children with SCD, even those with normal daytime SpO₂.     

Absolute Reticulocyte Count Acts as a Surrogate for Fetal Hemoglobin in Infants and Children with Sickle Cell Anemia

Hemoglobin switching is largely complete in humans by six months of age. Among infants with sickle cell anemia (HbSS, SCA), reticulocytosis begins early in life as fetal hemoglobin (HbF) is replaced by sickle hemoglobin (HbS). The objective of this study was to determine if absolute reticulocyte count (ARC) is related to HbF levels in a cohort of pediatric SCA patients. A convenience sample of 106 children with SCA between the ages of 1 month and 20 years who were not receiving hydroxyurea or monthly blood transfusions were enrolled in this observational study. Hematologic data, including ARC and HbF levels, were measured at steady state. F-cells were enumerated by flow cytometry. Initial studies compared infants with ARC greater than or equal to 200 K/μL (ARC ≥ 200) based upon the previously reported utility of this threshold as a predictive marker for SCA severity. Mean HbF and F-cell levels were significantly lower in the ARC ≥ 200 group when compared to the ARC < 200 group. Both HbF and F-cell percentages were negatively correlated to ARC in infants and in children between the ages of 1 and 9 years. However, the inverse relationship was lost after the age of 10 years. Overall, decreased expression and distribution of HbF during childhood SCA is well-correlated with increased reticulocyte production and release into the peripheral blood. As such, these data further support the clinical use of reticulocyte enumeration as a disease severity biomarker for childhood sickle cell anemia.     

Hematological and hemorheological Determinants of the Six-Minute Walk Test Performance in Children with Sickle Cell Anemia

The six-minute walk test is a well-established submaximal exercise reflecting the functional status and the clinical severity of sickle cell patients. The aim of the present cross-sectional study was to investigate the biological determinants of the six-minute walk test performance in children with sickle cell anemia. Hematological and hemorheological parameters, pulmonary function and the six-minute walk test performance were determined in 42 children with sickle cell anemia at steady state. The performance during the six-minute walk test was normalized for age, sex and height and expressed as percentage of the predicted six-minute walk distance. We showed that a high level of anemia, a low fetal hemoglobin expression and low red blood cell deformability were independent predictors of a low six-minute walk test performance. This study describes for the first time the impact of blood rheology in the six-minute walk test performance in children with sickle cell anemia.     

Continuous Positive Airway Pressure Treatment Reduces Mortality in Elderly Patients with Moderate to Severe Obstructive Severe Sleep Apnea: A Cohort Study

Obstructive sleep apnea (OSA) is much more prevalent in older people than in middle-aged or young populations, and has been associated with cardiovascular disease. Continuous positive airway pressure (CPAP) is the first-line therapy for OSA, but its long-term clinical benefit in the elderly is unclear. Here, we carried out a prospective cohort study to explore the survival rate and incidence of cardiovascular events in elderly patients with moderate to severe OSA who did or did not receive CPAP treatment. The study included 130 patients (104 male, 26 female; mean age: 77.8 ± 6.2 years) who were followed up for a mean of 5 ± 2.54 years (range, 1–8 years). Thirty-six patients received CPAP and 88 had no CPAP. The results showed that mortality in the untreated group (21.6%) was significantly higher than in the CPAP group (5.6%). Kaplan–Meier survival analysis showed that the survival rate in the CPAP group was 94.4%, which was markedly higher than the rate of 78.4% in the untreated group. The incidence of cardiovascular events was 13.9% in the CPAP group and 55.7% in the untreated group. The present study provides evidence that CPAP can reduce mortality in older patients with moderate to severe OSA, and lead to a good long-term prognosis. The study also indicates that death in older OSA patients is associated with cardiovascular disease and diabetes.     

Sleep-Disordered Breathing and Mortality: A Prospective Cohort Study

Background

Sleep-disordered breathing is a common condition associated with adverse health outcomes including hypertension and cardiovascular disease. The overall objective of this study was to determine whether sleep-disordered breathing and its sequelae of intermittent hypoxemia and recurrent arousals are associated with mortality in a community sample of adults aged 40 years or older.

Methods and Findings

We prospectively examined whether sleep-disordered breathing was associated with an increased risk of death from any cause in 6,441 men and women participating in the Sleep Heart Health Study. Sleep-disordered breathing was assessed with the apnea–hypopnea index (AHI) based on an in-home polysomnogram. Survival analysis and proportional hazards regression models were used to calculate hazard ratios for mortality after adjusting for age, sex, race, smoking status, body mass index, and prevalent medical conditions. The average follow-up period for the cohort was 8.2 y during which 1,047 participants (587 men and 460 women) died. Compared to those without sleep-disordered breathing (AHI: <5 events/h), the fully adjusted hazard ratios for all-cause mortality in those with mild (AHI: 5.0–14.9 events/h), moderate (AHI: 15.0–29.9 events/h), and severe (AHI: ≥30.0 events/h) sleep-disordered breathing were 0.93 (95% CI: 0.80–1.08), 1.17 (95% CI: 0.97–1.42), and 1.46 (95% CI: 1.14–1.86), respectively. Stratified analyses by sex and age showed that the increased risk of death associated with severe sleep-disordered breathing was statistically significant in men aged 40–70 y (hazard ratio: 2.09; 95% CI: 1.31–3.33). Measures of sleep-related intermittent hypoxemia, but not sleep fragmentation, were independently associated with all-cause mortality. Coronary artery disease–related mortality associated with sleep-disordered breathing showed a pattern of association similar to all-cause mortality.

Conclusions

Sleep-disordered breathing is associated with all-cause mortality and specifically that due to coronary artery disease, particularly in men aged 40–70 y with severe sleep-disordered breathing. Please see later in the article for the Editors'' Summary