Factors predicting future ACS episodes in children with sickle cell anemia

Lipid and hemolysis parameters predicting acute chest syndrome in adulthood with sickle cell disease

Sickle cell disease (SCD) is a lifelong blood disorder affecting approximately 100,000 people in the United States and is one of the most common monogenic diseases. A serious complication of SCD is acute chest syndrome (ACS). ACS is a condition with a high rate of morbidity and mortality. The aim of the study was to assess hemolysis and lipid parameters in a cohort of confirmed SCD patients to predict ACS development in the following year.Standard lipid were performed (triglycerides, total cholesterol, high-density cholesterol, low-density cholesterol) panel to calculate of non-HDL-C, large buoyant LDL cholesterol (lbLDL-C) and small dense LDL cholesterol (sdLDL-C) with Sampson equation. Hemolysis and hematologic parameters were also evaluated.Among 91 patients included between September 2018 and June 2021, thirty-seven patients had history of ACS and 6 patients developed ACS during following year. In unadjusted logistic regression, total bilirubin was associated with ACS occurrence (RR: 1.2 [1.05-1.51] p = 0.013). Concerning lipid profile, non-HDL-C (RR: 0.87 [0.0.67-0.99] p = 0.04) and sdLDL-C (RR: 0.78 [0.49-0.96] p = 0.03) were associated with ACS occurrence decrease. C-reactive protein was associated with ACS occurrence (RR: 1.27 [1.065-1.85] p = 0.011).Based on these findings, this study demonstrated that several biomarker easily available can be used at steady state to predict ACS in the following year. The validation of these results are required to ensure the reproducibility of the findings.

Description of a Colocated Comprehensive Care Model for People With Sickle Cell and Comorbid Pulmonary Disease

Comorbid pulmonary complications in people with sickle cell disease (pwSCD) are associated with high rates of morbidity and mortality, and poor access to care contributes to poor outcomes among this particularly high-risk pwSCD. Our purpose was to describe the population served and the resources required for hematology, pulmonary, nursing, respiratory therapy, social work, genetics, psychology, and school liaison providers to see these patients in an integrated clinic. We abstracted demographic, medication, clinical, and diagnostics data of the pwSCD seen at least once in this clinic from February 1, 2014 to December 10, 2020 from the electronic medical record and identified 145 unique pwSCD. Abnormal lung function and bronchodilator responsiveness were detected in 31% and 42% of participants respectively. Sleep abnormalities were found in over two-thirds of those screened and 65% had ≥1 previous acute chest syndrome episode. This clinic also allowed for direct provider communication and required relatively limited resources to serve a large number of severely affected pwSCD. Given the degree of abnormal respiratory variables detected and the limited resources required to implement this model, studies are warranted to evaluate whether it has the potential to improve outcomes in high-risk populations.

Predictors of Recurrent Acute Chest Syndrome in Pediatric Sickle Cell Disease: A Retrospective Case-Control Study

Acute chest syndrome (ACS) is a common cause of death in sickle cell disease (SCD) patients. Multiple studies investigated the risk factors of developing ACS; however, predictors of recurrent ACS episodes have not been thoroughly investigated. We aim to examine the clinical and laboratory predictors of recurrent ACS in pediatric patients with SCD. A retrospective case-control study included pediatric patients with SCD (˂14 years) admitted with ACS or developed ACS during admission for another indication. Patients were classified into recurrent ACS episodes (≥2 episodes) and a single ACS episode groups. Ninety-one ACS episodes (42 patients) were included, with a mean age at diagnosis of 7.18 ± 3.38 years. Twenty-two (52.4%) patients were male, and twenty-five (59.5%) patients had recurrent ACS. Younger age at first ACS was significantly associated with recurrence (p = 0.003), with an optimal cutoff at 7.5 years (area under the receiver operating characteristic curve [AUROC] = 0.833; p < 0.001). Higher SCD-related hospitalizations were significantly associated with recurrence (p = 0.038). Higher mean values of baseline white blood count (WBC) (p = 0.009), mean corpuscular volume (MCV) (p = 0.011), and reticulocyte (p = 0.036) were significantly associated with recurrence. Contrarily, lower baseline hematocrit values (p = 0.016) were significantly associated with recurrence. The ACS frequencies were significantly lower after hydroxyurea (p = 0.021). The odds of ACS recurrence increased with a positive C-reactive protein (CRP) at admission (p = 0.006). In conclusion, several baseline and admission laboratory data showed significant associations with recurrence. Hydroxyurea therapy demonstrated reduced ACS episodes.

Benefit of pulmonary subspecialty care for children with sickle cell disease and asthma

OBJECTIVE

Asthma is a recognized comorbidity in children with sickle cell disease (SCD). It increases the risk of acute chest syndrome (ACS), vaso-occlusive episodes, and early mortality. We aim to determine whether evaluation and management of children with SCD and asthma by a pulmonologist reduce rate of asthma exacerbation and ACS.

METHODS

The study included 192 patients with SCD (0-21 years) followed at Children's Hospital of Philadelphia Hematology between January 1, 2015, and December 31, 2018, with a diagnosis of asthma, wheeze, or cough. Patients were placed in two groups: those evaluated by a pulmonologist (SCD-A-P) and those not (SCD-A). Rates of emergency department (ED) visits and hospitalizations for asthma exacerbation and ACS were compared between groups and over time.

RESULTS

SCD-A-P patients (n = 70) were predominantly SCD type SS with lower hemoglobin and hematocrit compared to SCD-A patients (n = 122). SCD-A-P started with a higher average rate of hospital visits for asthma exacerbation and ACS per year (2.69 [1.02-4.37]) compared to SCD-A (0.43 [0.24-0.63]), (p < 0.001). For SCD-A-P patients with at least one hospital visit (n = 48), the average rate decreased from 3.93 (1.57-6.29) to 0.85 (0.48-1.23) following pulmonary consultation (p = 0.014) and was comparable to the SCD-A rate by study end.

CONCLUSION

SCD-A-P was mainly SCD type SS and had higher ED/hospitalization rates for asthma exacerbation and ACS compared to SCD-A, but the rates significantly decreased following pulmonology consultation. These findings support the pulmonologist's role in the multidisciplinary care of SCD patients and highlight the need for evidence-based asthma guidelines for children with SCD.

Acute chest syndrome of sickle cell disease: genetics, risk factors, prognosis and management

IntroductionSickle cell disease, one of the world's most prevalent Mendelian disorders, is a chronic hemolytic anemia punctuated by acute vasoocclusive events. Both hemolysis and vasoocclusion lead to irreversible organ damage and failure. Among the many sub-phenotypes of sickle cell disease is the acute chest syndrome (ACS) characterized by combinations of chest pain, cough, dyspnea, fever, abnormal lung exam, leukocytosis, hypoxia, and new radiographic opacities. ACS is a major cause of morbidity and mortality.Area coveredWe briefly review the diagnosis, epidemiology, etiology, and current treatments for ACS and focus on understanding and estimating the risks for developing this complication, how prognosis and outcomes might be improved and the genetic elements that might impact the risk of ACS.Expert opinionThe clinical heterogeneity of ACS has hindered our understanding of risk stratification. Lacking controlled clinical trials most treatment is based on expert opinion. Fetal hemoglobin levels and coexistent α thalassemia affect the incidence of ACS; other genetic associations are tenuous. Transfusions, whose use not innocuous, should be targeted to the severity and likelihood of ACS progression. Stable, non-hypoxic patients with favorable hematologic and radiographic findings usually do not need transfusion; severe progressive ACS is best managed with exchange transfusion.

Lung Clearance Index May Detect Early Peripheral Lung Disease in Sickle Cell Anemia

RATIONALE

Chronic lung injury is common in sickle cell anemia (SCA) and worsens outcomes. Sensitive lung function tests might predict reversible disease that might benefit from therapeutic interventions.

OBJECTIVE

To evaluate whether Lung Clearance Index (LCI), S_acin & S_cond, measuring global, intracinar & conductive ventilation inhomogeneity respectively, are more frequently abnormal than lung volumes in young people with SCA.

METHODS

Nitrogen multiple breath washout, spirometry and body plethysmography were cross-sectionally evaluated at steady state in subjects with SCA (hemoglobin SS) and healthy controls aged 8-21 years from London, UK.

RESULTS

35 patients (51% boys; mean±SD 16.4±3.5 years) and 31 controls (48% boys; 16.2±3.2 years) were tested. There were significant differences between the study and control group in mean LCI (mean difference 0.42 units, 95%CI 0.22 to 0.63, p = 0.0001), S_acin (mean difference 0.014 units, 95%CI 0.001 to 0.026, p = 0.04), FEV₁ (mean difference -0.79 z-scores, 95%CI -1.28 to -0.30, p = 0.002), FVC (mean difference -0.80 z-scores, 95%CI -1.28 to -0.31) and TLC (mean difference -0.79 z-scores, 95%CI -1.25 to -0.29), but not in S_cond and FEV₁/FVC ratio. While 29% (10/35) of patients had LCI >95th percentile of controls, 23% (8/35) had abnormal FEV₁ (<5th of the reference population).

CONCLUSION

Lung clearance index detected slightly more abnormalities than lung volumes in young people with SCA. Significant differences with controls in LCI and S_acin but not in S_cond and FEV₁/FVC ratio suggest that the lung function changes were most likely due to patchy peripheral lung disease.

A systematic literature review of frequency of vaso-occlusive crises in sickle cell disease

BACKGROUND AND PURPOSE

Sickle cell disease (SCD) is a collection of rare inherited blood disorders affecting approximately 100,000 people in the U.S. and 20-25 million people globally. Individuals with SCD experience recurrent episodes of severe and unpredictable pain that are caused by vaso-occlusive crises (VOCs), a hallmark of the disease. VOCs are the primary cause of hospitalization in SCD, result in missed workdays and school days, and decrease quality of life (QoL). Although VOCs cause significant burden in the lives of individuals with SCD, there is no synthesis on the frequency of VOCs in the real world. This systematic literature review sought to identify literature describing the frequency of VOCs experienced by individuals with SCD in real-world settings.

METHODS

MEDLINE and 6 congresses were searched (date range: January 1, 2000 to June 30, 2020). Studies were reviewed independently by two researchers. Studies assessing frequency or prevalence of VOCs or VOC-related outcomes were included.

RESULTS

Of 1438 studies identified in the search, 52 met pre-specified inclusion and exclusion criteria. Reported frequency of VOCs varied widely ranging from a mean or median of 0 VOCs/year to 18.2 VOCs/year. The proportion of patients experiencing ≥ 3 VOCs/year ranged from 4 to 67% and the proportion of patients experiencing ≥ 5 VOCs/year ranged from 18 to 59%. Measures of VOC severity were limited, with 13 studies considering frequency of complicated VOCs and only 1 study reporting duration of VOC episodes.

CONCLUSIONS

This is the first study to systematically assess published evidence pertaining to VOCs in real-world settings. Reported VOC frequency in real-world settings varied widely, with a majority of studies only considering VOCs managed in an inpatient or outpatient setting. Studies that considered VOCs managed at home reported a higher frequency of VOCs, suggesting that many studies may underestimate the frequency of VOCs. This systematic literature review (SLR) highlights the need for consistent reporting of (1) self-reported VOCs, including those managed at home, (2) definitions of VOCs, (3) complicated VOCs, and (4) duration of VOC episodes in literature.

SNAP: Supportive noninvasive ventilation for acute chest syndrome prevention in children with sickle cell disease

BACKGROUND

Acute chest syndrome (ACS) is a leading cause of morbidity and mortality among children with sickle cell disease (SCD). Preventing hypoxemia by optimizing lung aeration during sleep remains a challenge.

OBJECTIVES

To explore safety, feasibility, and tolerability of noninvasive, bi-level positive airway pressure ventilation (BiPAP) as preventative, supportive care for hospitalized, medically stable children with SCD on a general pediatric inpatient unit.

METHODS

Retrospective chart review of patients ≤22 years of age with SCD admitted to the general pediatric inpatient unit from February 1, 2017 to March 1, 2020 for whom BiPAP was recommended as supportive care. Hospitalizations were excluded if patients were admitted to the pediatric intensive care unit (PICU), required BiPAP for respiratory failure, or used BiPAP at home for obstructive sleep apnea.

RESULTS

Twenty-three patients had 53 hospitalizations in which BiPAP was recommended. Fifty-two (98%) hospitalizations included acute SCD pain. Indications for BiPAP included prior ACS (94%), chest or back pain (79%), and/or oxygen desaturation (66%). On 17 occasions, patients already had mild to moderate ACS but were stable when BiPAP was recommended. BiPAP was used successfully during 75% of hospitalizations for a median of two nights. There were no adverse effects associated with BiPAP. PICU transfer for respiratory support occurred during three hospitalizations. In 26 hospitalizations of children at risk for ACS who tolerated BiPAP, 23 (88%) did not develop ACS.

CONCLUSIONS

BiPAP is safe, feasible, and well tolerated as supportive care for hospitalized children with SCD. Next steps include an intervention trial to further assess the efficacy of BiPAP on ACS prevention.

Circulating extracellular vesicles from patients with acute chest syndrome disrupt adherens junctions between endothelial cells

BACKGROUND

Small cell-derived extracellular vesicles (EVs) can affect endothelial function. We previously found that patients with sickle cell disease (SCD) have greater numbers of circulating EVs than subjects without the disease, and the EVs differentially disrupt endothelial integrity in vitro. Because endothelial disruption is a critical component of acute chest syndrome (ACS), we hypothesized that EVs isolated during ACS would induce greater endothelial damage than those isolated at baseline.

METHODS

Nine pediatric subjects had plasma isolated at baseline and during ACS from which EVs were isolated. Cultured microvascular endothelial cells were treated with EVs and then studied by immunofluorescence microscopy to localize VE-cadherin and F-actin.

RESULTS

The EVs had a diameter of 95 nm. They contained CD63 and flotillin-1, which were increased in SCD patients (5-13-fold compared to control) and further increased between baseline and ACS (24-57%). The EVs contained hemoglobin, glycophorin A, and ferritin. Treatment with baseline EVs caused modest separation of endothelial cells, while ACS EVs caused substantial disruptions of the endothelial cell monolayers. EVs from subjects with ACS also caused a 50% decrease in protein levels of VE-cadherin.

CONCLUSIONS

These results suggest that circulating EVs can modulate endothelial integrity contributing to the development of ACS in SCD patients by altering cadherin-containing intercellular junctions.

IMPACT

Sickle cell disease patients have circulating extracellular vesicles (EVs) that modulate endothelial integrity by altering cadherin-containing intercellular junctions. Disruption is more severe by EVs obtained during acute chest syndrome (ACS). These results expand our knowledge of the pathophysiology of acute chest syndrome and the vasculopathies of sickle cell disease.

Asthma, allergic sensitization and lung function in sickle cell disease

BACKGROUND

Pulmonary disease is a frequent acute and chronic manifestation in sickle cell disease (SCD), presenting high morbidity and mortality.

OBJECTIVES

To identify the prevalence and association of asthma, allergic sensitization and altered pulmonary function in patients with SCD (SS and Sβ^o).

METHODS

A single-center, cross-sectional study was conducted, in which 70 patients with SCD and 44 controls, aged six to 18 years, responded to the questionnaire of the International Study of Asthma and Allergies in Childhood (ISAAC), complemented with an anamnesis regarding the associated clinical outcomes. All patients underwent immediate hypersensitivity skin tests with aeroallergens and a pulmonary function evaluation (spirometry). Regarding the statistical analysis, parametric and non-parametric methods were used, depending on the variables studied. Tests were considered significant when p<0.05.

RESULTS

There was no significant difference between the patients and controls regarding the prevalence of asthma and allergic sensitization (p>0.05). The number of occurrences of acute chest syndrome per patient per year was significantly higher for asthmatic patients than for non-asthmatic patients (p=0.04). Obstructive pulmonary function occurred in 30.9% of the patients and in 5.4% of the controls, and restrictive pulmonary function occurred in 5.5% of the patients and 5.4% of the controls. Asthma and wheezing in the last 12months had significant associations with obstructive pulmonary function (p=0.014 and p=0.027, respectively).

CONCLUSIONS

The occurrence of asthma, allergic sensitization and alteration in lung function in patients with SCD reinforces the importance of routine monitoring of these diagnoses, which allows for early treatment and prevention of the evolution of pulmonary disease in adulthood.

Pulmonary disease burden in Hispanic and non-Hispanic children with sickle cell disease

RATIONALE

Pulmonary complications are the leading cause of morbidity and mortality in sickle cell disease (SCD) patients. Research in SCD has predominantly been conducted on African-Americans, and the disease burden of SCD in other races and ethnicities, including Hispanic patients, is not well characterized.

OBJECTIVE

To compare pulmonary disease burden between Hispanic and non-Hispanic ethnic groups among children with SCD.

METHODS

In a retrospective chart review on 566 SCD patients followed at the Children's Hospital at Montefiore, NY, we compared the pulmonary disease burden and disease management in Hispanic patients to their non-Hispanic counterparts. We also compared the contribution of demographic and clinical variables to acute chest syndrome (ACS), vaso-occlusive crisis (VOC), and hospitalizations for SCD related complications between the two ethnic groups.

RESULTS

Hispanic patients had a greater proportion of ACS, and had lower forced expiratory volume (FEV1), forced vital capacity, and vital capacity, compared to non-Hispanics. Hispanic patients were more likely to be evaluated in pulmonary clinic and to be on inhaled corticosteroids, short-acting β agonizts, and leukotriene receptor antagonists. In addition, Hispanic children were more likely to be on hydroxyurea, and receive exchange transfusions. However, the association of asthma with the proportion of ACS did not differ between Hispanics and non-Hispanics.

CONCLUSION

Hispanic children with SCD had differences in their pulmonary function profile and received more pulmonary evaluations than non-Hispanic children.

Validation of the breathmobile case identification survey for asthma screening in children with sickle cell disease

Background: Asthma is a chronic airway disorder with variable/recurring symptoms, airflow obstruction, bronchial hyperresponsiveness, and an inflammation. The expert panel report of the National Heart Lung and Blood Institute recommends asthma screening in sickle cell disease (SCD); however, specific approach is not mentioned. We hypothesize that the breathmobile case identification survey (BCIS) is a valid asthma screening tool in children with SCD.Methods: This prospective, single-center study enrolled 129 SCD patients aged 5 to 18 years from March 2016 to March 2018. All patients completed BCIS, spirometry, and fractional exhaled nitric oxide (FeNO). A single pulmonologist blinded to the BCIS results evaluated patients for asthma.Results: Asthma prevalence was 41%. Male gender (60.4%; p = 0.041), allergic rhinitis (86.8%; p < 0.01), hydroxyurea usage (73.6%; p < 0.01), and family history of asthma (34%; p < 0.01) were higher but not self-reported parental asthma history, eczema, and tobacco smoke exposure in the asthma group compared to the nonasthma group. FEV₁ (p = 0.003), FVC (p = 0.02), FEV₁/FVC (p = 0.053), and FEF_25-75% (p = 0.02) were lower in asthma. FeNO levels were comparable in both groups. The sensitivity, specificity, positive predictive value, and negative predictive value of the abbreviated BCIS were 67.3%, 90.8%, 83.3%, and 80.2% for asthma; and 82.1%, 90.8%, 76.7%, and 93.2% for persistent asthma, respectively. Persistent asthma patients had a trend of higher hydroxyurea use (82.8% vs. 58.3%; p = 0.049) and tobacco smoke exposure (55.2% vs. 29.2%; p = 0.057) compared to intermittent asthma.Conclusion: We have validated the BCIS to screen for asthma in SCD. Spirometry but not FeNO may support an asthma diagnosis.

Predictors of impending acute chest syndrome in patients with sickle cell anaemia

Acute chest syndrome (ACS) is a major complication of sickle cell anaemia (SCA) and a leading cause for hospital admissions and death. We aimed to study the spectrum of clinical and laboratory features of ACS and to assess the predisposing factors and predictors of severity. A retrospective case-control cohort was studied by retrieving patient information from electronic medical records after ethical approval. One hundred adolescents and adults with SCA and hospital admissions for ACS were identified through the discharge summaries, along with 20 additional patients presenting with VOC, but without ACS (controls). Among the patients with ACS, fever (>38.5 °C), reduced oxygen saturation (<95) and asplenia significantly differed when compared to those of controls (p < 0.05, chi-squared test). The degree of severity was reflected in the use of non-invasive ventilation (NIV), simple and exchange transfusions, and the presence of bilateral pleural effusions and multi-lobar atelectasis/consolidation, which were significantly higher in the cases with ACS than in the controls. Lower haemoglobin (Hb) and high WBC counts were also significantly different between the two groups (p < 0.05, Student's t test). Using logistic regression, our study further demonstrated that asplenia, fever, and reduced O₂ saturation, along with low Hb and leukocytosis, were important predictors for the development of ACS.

Convergence of Inflammatory Pathways in Allergic Asthma and Sickle Cell Disease

The underlying pathologies of sickle cell disease and asthma share many characteristics in terms of respiratory inflammation. The principal mechanisms of pulmonary inflammation are largely distinct, but activation of common pathways downstream of the initial inflammatory triggers may lead to exacerbation of both disease states. The altered inflammatory landscape of these respiratory pathologies can differentially impact respiratory pathogen susceptibility in patients with sickle cell disease and asthma. How these two distinct diseases behave in a comorbid setting can further exacerbate pulmonary complications associated with both disease states and impact susceptibility to respiratory infection. This review will provide a concise overview of how asthma distinctly affects individuals with sickle cell disease and how pulmonary physiology and inflammation are impacted during comorbidity.

Vaso-Occlusion in Sickle Cell Disease: Is Autonomic Dysregulation of the Microvasculature the Trigger?

Sickle cell disease (SCD) is an inherited hemoglobinopathy characterized by polymerization of hemoglobin S upon deoxygenation that results in the formation of rigid sickled-shaped red blood cells that can occlude the microvasculature, which leads to sudden onsets of pain. The severity of vaso-occlusive crises (VOC) is quite variable among patients, which is not fully explained by their genetic and biological profiles. The mechanism that initiates the transition from steady state to VOC remains unknown, as is the role of clinically reported triggers such as stress, cold and pain. The rate of hemoglobin S polymerization after deoxygenation is an important determinant of vaso-occlusion. Similarly, the microvascular blood flow rate plays a critical role as fast-moving red blood cells are better able to escape the microvasculature before polymerization of deoxy-hemoglobin S causes the red cells to become rigid and lodge in small vessels. The role of the autonomic nervous system (ANS) activity in VOC initiation and propagation has been underestimated considering that the ANS is the major regulator of microvascular blood flow and that most triggers of VOC can alter the autonomic balance. Here, we will briefly review the evidence supporting the presence of ANS dysfunction in SCD, its implications in the onset of VOC, and how differences in autonomic vasoreactivity might potentially contribute to variability in VOC severity.

Identifying Clinical and Research Priorities in Sickle Cell Lung Disease. An Official American Thoracic Society Workshop Report

Background: Pulmonary complications of sickle cell disease (SCD) are diverse and encompass acute and chronic disease. The understanding of the natural history of pulmonary complications of SCD is limited, no specific therapies exist, and these complications are a primary cause of morbidity and mortality.Methods: We gathered a multidisciplinary group of pediatric and adult hematologists, pulmonologists, and emergency medicine physicians with expertise in SCD-related lung disease along with an SCD patient advocate for an American Thoracic Society-sponsored workshop to review the literature and identify key unanswered clinical and research questions. Participants were divided into four subcommittees on the basis of expertise: 1) acute chest syndrome, 2) lower airways disease and pulmonary function, 3) sleep-disordered breathing and hypoxia, and 4) pulmonary vascular complications of SCD. Before the workshop, a comprehensive literature review of each subtopic was conducted. Clinically important questions were developed after literature review and were finalized by group discussion and consensus.Results: Current knowledge is based on small, predominantly observational studies, few multicenter longitudinal studies, and even fewer high-quality interventional trials specifically targeting the pulmonary complications of SCD. Each subcommittee identified the three or four most important unanswered questions in their topic area for researchers to direct the next steps of clinical investigation.Conclusions: Important and clinically relevant questions regarding sickle cell lung disease remain unanswered. High-quality, multicenter, longitudinal studies and randomized clinical trials designed and implemented by teams of multidisciplinary clinician-investigators are needed to improve the care of individuals with SCD.

Asthma in children with sickle cell disease

PURPOSE OF REVIEW

Asthma is common in children with sickle cell disease (SCD) and appears to be associated with increased morbidity. Providers caring for children with SCD have struggled with the question of whether asthma exists as a true comorbidity or whether certain aspects of the chronic inflammatory disease gives children with SCD an asthma-like phenotype.

RECENT FINDINGS

Clinical signs and symptoms seen in children with asthma in the general population, such as wheezing, airway hyperresponsiveness, atopy, elevated leukotrienes, and abnormal lung function are seen in children with SCD both with and without a diagnosis of asthma.

SUMMARY

Current evidence highlights that the presence of lung disease in children with SCD has significant implications irrespective of the underlying cause, including asthma. Further research should focus on well tolerated and effective interventions to prevent disease-related complications for children with pulmonary complications of SCD.

Sickle cell disease: Clinical presentation and management of a global health challenge

Sickle cell disease is an autosomal recessive, multisystem disorder, characterised by chronic haemolytic anaemia, painful episodes of vaso-occlusion, progressive organ failure and a reduced life expectancy. Sickle cell disease is the most common monogenetic disease, with millions affected worldwide. In well-resourced countries, comprehensive care programs have increased life expectancy of sickle cell disease patients, with almost all infants surviving into adulthood. Therapeutic options for sickle cell disease patients are however, still scarce. Predictors of sickle cell disease severity and a better understanding of pathophysiology and (epi)genetic modifiers are warranted and could lead to more precise management and treatment. This review provides an extensive summary of the pathophysiology and management of sickle cell disease and encompasses the characteristics, complications and current and future treatment options of the disease.

Sickle Cell Disease: Monitoring, Current Treatment, and Therapeutics Under Development

Screening and early detection of organ injury, as well as expanded use of red cell transfusion and hydroxyurea in children have changed best practices for clinical care in sickle cell disease. The current standard of care for children with sickle cell disease is discussed through a review of screening recommendations, disease monitoring, and approach to treatment. Novel pharmacologic agents under investigation in clinical trials are also reviewed.

Pulmonary dysfunction among adolescents and adults with sickle cell disease in Nigeria: Implications for monitoring

BACKGROUND:

Pulmonary complications of sickle cell disease (SCD) contribute to excess morbidity and mortality. The burden of pulmonary dysfunction among Nigerians with SCD has not been well elucidated.

OBJECTIVES:

The objectives of this study are to describe the frequency and pattern of spirometry abnormalities in SCD and to explore the association between pulmonary dysfunction and selected parameters.

METHODS:

A cross-sectional study among adolescents and adults with SCD attending a University Teaching Hospital and healthy age- and gender-matched controls. Respiratory symptoms, oxygen saturation, spirometry, complete blood counts, and fetal hemoglobin (Hb) were measured.

RESULTS:

A total of 245 participants with SCD and 216 controls were included in the study. Frequency of respiratory symptoms was similar between the two groups. The median forced expiratory volume 1 (FEV1), forced vital capacity (FVC), and the FEV1/FVC were significantly lower in SCD as compared to controls (P = 0.000 in all instances). The frequency of abnormal pulmonary patterns was higher in SCD as compared to controls with abnormal spirometry pattern in 174 (71%) and 68 (31.5%) of participants with SCD and controls, respectively (P = 0.000). The suggestive of restrictive pattern was predominant (48% vs. 23%), but obstructive (11.8% vs. 7.4%) and mixed patterns (11% vs. 0.9%) were also found among SCD versus controls. Hb concentration was positively associated with FEV1 and FVC, whereas white cell count and age were negatively associated with FVC and FEV1, respectively.

CONCLUSION:

There is a high burden of pulmonary dysfunction in SCD among Nigerians which may be related to the severity of disease. There is a need for further research to explore the effectiveness of potential interventions so as to harness the benefits from monitoring and early detection.

Airway inflammation in sickle cell disease-A translational perspective

Asthma and sickle cell disease (SCD) are common chronic conditions in children of African ancestry that are characterized by cough, wheeze, and obstructive patterns on pulmonary function. Pulmonary function testing in children with SCD has estimated a prevalence of obstructive lung disease ranging from 13% to 57%, and airway hyper-responsiveness of up to 77%, independent of a diagnosis of asthma. Asthma co-existing with SCD is associated with increased risk of acute chest syndrome (ACS), respiratory symptoms, pain episodes, and death. However, there are inherent differences in the pathophysiology of SCD and asthma. While classic allergic asthma in the general population is associated with a T-helper 2 cell (Th-2 cells) pattern of cell inflammation, increased IgE levels and often positive allergy testing, inflammation in SCD is associated with different inflammatory pathways, involving neutrophilic and monocytic pathways, which have been explored to a limited extent in mouse models and with a dearth of human studies. The current review summarizes the existent literature on sickle cell related airway inflammation and its cross roads with allergic asthma-related inflammation, and discusses the importance of further elucidating and understanding these common and divergent inflammatory pathways in human studies to facilitate development of targeted therapy for children with SCD and pulmonary morbidity.

Age is a predictor of a small decrease in lung function in children with sickle cell anemia

The longitudinal pattern of lung function in children with sickle cell anemia (SCA) has shown a decrease in FEV₁ % predicted, a risk factor for death in adults with SCA, but predictors for this decline are poorly characterized. In a prospective longitudinal multi-center cohort of children with SCA, we tested the hypotheses that: (1) FEV₁ % predicted declines over time; and (2) SCA-specific characteristics and therapy predict this decline. At three clinical centers, children with SCA (HbSS or HbSβ⁰ thalassemia), unselected for respiratory disease, were enrolled in the Sleep and Asthma Cohort (SAC) study. Study-certified pulmonary function technicians performed spirometry and lung volumes. Each assessment was reviewed centrally. Predicted values were determined for TLC, FEV₁ , FVC, and FEV₁ /FVC ratio. A total of 197 participants, mean age 11.0 years at first testing (range 4-19.3 years), had a minimum of three spirometry measurements, over an average of 4.4 years (range 1.1-6.5 years) from baseline to endpoint. In a multivariable model, FEV₁ % predicted declines by 0.3% for every additional year of age (95% CI -0.56 to -0.05, P = .020). Sex, asthma history, hemoglobin, reticulocyte count, white blood cell count, incidence rate of severe acute pain and acute chest syndrome episodes, and hydroxyurea therapy were not associated with a decline in FEV₁ % predicted. In a large, rigorously evaluated, prospective cohort of an unselected group of children with SCA, FEV₁ % predicted declines minimally over an average of 4 years, and none of the examined disease features predict the decline.

Aeroallergen sensitization predicts acute chest syndrome in children with sickle cell anaemia

Asthma is associated with higher rates of acute chest syndrome (ACS) and vaso-occlusive pain episodes among children with sickle cell anaemia (SCA). Aeroallergen sensitization is a risk factor for asthma. We hypothesized that aeroallergen sensitization is associated with an increased incidence of hospitalizations for ACS and pain. Participants in a multicentre, longitudinal cohort study, aged 4-18 years with SCA, underwent skin prick testing to ten aeroallergens. ACS and pain episodes were collected from birth until the end of the follow-up period. The number of positive skin tests were tested for associations with prospective rates of ACS and pain. Multivariable models demonstrated additive effects of having positive skin tests on future rates of ACS (incidence rate ratio (IRR) for each positive test 1·23, 95% confidence interval [CI] 1·11-1·36, P < 0·001). Aeroallergen sensitization was not associated with future pain (IRR 1·14, 95%CI 0·97-1·33, P = 0·11). Our study demonstrated that children with SCA and aeroallergen sensitization are at increased risk for future ACS. Future research is needed to determine whether identification of specific sensitizations and allergen avoidance and treatment reduce the risk of ACS for children with SCA.

Recurrent Acute Chest Syndrome in Pediatric Sickle Cell Disease: Clinical Features and Risk Factors

Acute chest syndrome (ACS) is a common and serious lung complication in sickle cell disease. A retrospective medical chart review was performed over a 6-year period in all pediatric ACS patients to investigate whether factors during the initial hospitalization were associated with recurrent ACS episodes. There were 386 episodes of ACS: 149 had only 1 episode of ACS, and 76 had >1 episode of ACS; 172 (76.4%) had hemoglobin SS, and 39 (17.3%) had hemoglobin SC. The most common presenting features were fever (83%), pain (70%), and cough (61%), which changed with the number of ACS episodes. Children <4 years old were at greatest risk of recurrent ACS (P=0.018). In addition, history of asthma (adjusted incident rate ratio [IRR]=1.52; 95% confidence interval [CI], 1.22-1.98; P<0.0001), shortness of breath (IRR, 1.29; 95% CI, 1.02-1.62; P=0.033), and length of hospital stay (IRR, 1.04; 95% CI, 1.01-1.08; P=0.017) were significantly associated with prospective ACS events. Multiple episodes of ACS are common in sickle cell disease, and certain risk factors during the initial hospitalization are associated with recurrent ACS.

Current Standards of Care and Long Term Outcomes for Thalassemia and Sickle Cell Disease

Thalassemia and sickle cell disease (SCD) are disorders of hemoglobin that affect millions of people worldwide. The carrier states for these diseases arose as common, balanced polymorphisms during human history because they afforded protection against severe forms of malaria. These complex, multisystem diseases are reviewed here with a focus on current standards of clinical management and recent research findings. The importance of a comprehensive, multidisciplinary and lifelong system of care is also emphasized.

Pediatric sickle cell disease: past successes and future challenges

Once a fatal disease of childhood, more than 95% of patients born today with sickle cell disease (SCD) in developed countries are expected to survive into adulthood, largely because of improvements in supportive and preventive care (newborn screening, penicillin prophylaxis, transcranial Doppler (TCD) screening). Hydroxyurea (HU) therapy, the only oral medication currently available to prevent SCD complications, has become more widespread over the past 20 y. The NHLBI recommends that HU be offered to all patients with HbSS beginning at 9 mo of age, and the recently published Abnormal TCD with Transfusions Changing to HU (TWiTCH) trial has shown HU as an acceptable alternative to transfusion therapy for patients at high risk of stroke. While hematopoietic stem cell transplant (HSCT) is a curative option for SCD, less than 25% of patients have a suitable donor. Alternative stem cell sources from unrelated donors and haplo-identical donors are currently under investigation as are gene therapy trials. This review will focus on early efforts to elucidate SCD pathophysiology as well as supportive and preventive care improvements. Findings from recent multi-center studies (Silent Infarct Transfusion (SIT) Trial and TWiTCH) will be summarized. Finally, HSCT trials and gene therapy will be reviewed.

Exhaled nitric oxide: Not associated with asthma, symptoms, or spirometry in children with sickle cell anemia

BACKGROUND

The significance of fractional exhaled nitric oxide (Feno) levels in children with sickle cell anemia (SCA) is unclear, but increased levels can be associated with features of asthma and thus increased morbidity.

OBJECTIVES

We sought to determine factors associated with Feno and whether Feno levels are associated with increased rates of acute chest syndrome (ACS) and pain.

METHODS

All participants had SCA, were part of the prospective observational Sleep and Asthma Cohort study, and had the following assessments: Feno levels, spirometry, blood samples analyzed for hemoglobin, white blood cell counts, eosinophil counts and total serum IgE levels, questionnaires about child medical and family history, and review of medical records.

RESULTS

The analytic sample included 131 children with SCA (median age, 11.2 years; age range, 6-18 years) followed for a mean of 16.2 years, including a mean of 5.1 years after baseline Feno data measurements. In multivariable analyses higher Feno levels were associated with ln(IgE) levels (P < .001) and the highest quartile of peripheral eosinophil counts (P = .03) but not wheezing symptoms, baseline spirometric indices, or response to bronchodilator. Multivariable analyses identified that the incident rate of ACS was associated with ln(Feno) levels (P = .03), as well as male sex (P = .025), wheezing causing shortness of breath (P = .002), and ACS at less than 4 years of age (P < .001). Feno levels were not associated with future pain episodes.

CONCLUSIONS

Steady-state Feno levels were not associated with an asthma diagnosis, wheezing symptoms, lung function measures, or prior sickle cell morbidity but were associated with markers of atopy and increased risk of future ACS events.

The intersection between asthma and acute chest syndrome in children with sickle-cell anaemia

Acute chest syndrome is a frequent cause of acute lung disease in children with sickle-cell disease. Asthma is common in children with sickle-cell disease and is associated with increased incidence of vaso-occlusive pain events, acute chest syndrome episodes, and earlier death. Risk factors for asthma exacerbation and an acute chest syndrome episode are similar, and both can present with shortness of breath, chest pain, cough, and wheezing. Despite overlapping risk factors and symptoms, an acute exacerbation of asthma or an episode of acute chest syndrome are two distinct entities that need disease-specific management strategies. Although understanding has increased about asthma as a comorbidity in sickle-cell disease and its effects on morbidity, substantial gaps remain in knowledge about best management.

Original Research: Acute chest syndrome in sickle cell disease: Effect of genotype and asthma

Sickle cell disease is a severe hemoglobinopathy caused by mutations in the beta globin genes. The disorder has protean manifestations and leads to severe morbidity and early mortality. Acute chest syndrome (ACS) is a common complication and in the USA is the leading cause of death in patients with sickle cell disease. Care of patients with sickle cell disease is complex and typically involves both primary care physicians and hematology subspecialists. The purpose of this study was first to attempt to validate in a pediatric sickle cell patient cohort associations between ACS and sickle cell disease genotype and between ACS and asthma as a comorbidity. The second purpose of the study was to study in a typical community the frequency with which asthma associated with ACS was addressed in terms of electronic medical record integration, pulmonary subspecialty consultation for management of asthma, and completion of pulmonary function testing (PFTs). A retrospective study of the electronic medical record of a children's hospital that provides most of the medical care for children in a portion of western New York state was performed. We found that ACS was more common in the sickle cell disease genotypes SS and S/beta-thalassemia-null, and that ACS was more frequent in patients treated for asthma. We also found that despite the use of a comprehensive electronic medical record, there was poor documentation of ACS and asthma episodes in the problem lists of patients with sickle cell disease, and that most patients with sickle cell disease with ACS or asthma failed to receive formal consultation services from pediatric pulmonary subspecialists.

Sickle cell disease: wheeze or asthma?

Sickle cell disease (SCD) is the most common life-limiting genetic disease among African Americans, affecting more than 100,000 people in the United States. Respiratory disorders in patients with sickle cell disease have been associated with increased morbidity and mortality. Associations between asthma and pain, acute chest syndrome (ACS), and even death have long been reported. More recently wheezing, even in the absence of an asthma diagnosis, has gained attention as a possible marker of SCD severity. Several challenges exist with regards to making the diagnosis of asthma in patients with SCD, including the high prevalence of wheezing, evidence of airway obstruction on pulmonary function testing, and/or airway hyperresponsiveness among patients with SCD. These features often occur in isolation, in the absence of other clinical criteria necessary for an asthma diagnosis. In this review we will summarize: 1) Our current understanding of the epidemiology of asthma, wheezing, airway obstruction, and airway responsiveness among patients with SCD; 2) The evidence supporting associations with SCD morbidity; 3) Our understanding of the pathophysiology of airway inflammation in SCD; 4) Current approaches to diagnosis and management of asthma in SCD; and 5) Future directions.

Prevention of Morbidity in sickle cell disease--qualitative outcomes, pain and quality of life in a randomised cross-over pilot trial of overnight supplementary oxygen and auto-adjusting continuous positive airways pressure (POMS2a): study protocol for a randomised controlled trial

BACKGROUND

Sickle cell anaemia (SCA) is an inherited disorder of haemoglobin. Patients experience long-term health care problems, affecting quality of life (QOL) including frequent acute pain, which is difficult to document in trials except as hospital admissions. Pilot data suggests that overnight respiratory support, either supplementary oxygen or auto-adjusting continuous positive airways pressure (APAP), is safe and may have clinical benefit. This pilot trial aims to determine which intervention is more acceptable to participants and whether there are other advantages of one over the other, e.g. in respiratory function or haematological parameters, before conducting the Phase 2 trial of overnight respiratory support funded by the National Institutes of Health Research.

METHODS/DESIGN

This is a pilot cross-over interventional trial with the order of interventions decided by simple randomization. Ten adults (age over 18 years) and 10 children (aged between 8 and 18 years) with homozygous sickle cell disease (haemoglobin SS, HbSS), recruited regardless of symptoms of sleep-disordered breathing, will undergo overnight pulse oximetry and will have two interventions, overnight oxygen and APAP, for a week each in randomised order with a washout week between interventions. Participants will complete online diaries via an iPad throughout the 29 days of the study and will complete QOL questionnaires and have measurement of haematology, biochemistry, spirometry and lung volumes (adults only) at 3 time points, at baseline and after each intervention, as well as in-depth semi-structured qualitative interviews after each intervention, carried out by an experienced psychologist. Both qualitative and statistical methods will be used to analyze the data. The primary outcome is qualitative data looking at participant experience from the transcribed interviews after each intervention. The participant's view on feasibility, acceptability and preference will specifically be explored. The QOL, laboratory and lung function data will be compared with baseline for each arm.

DISCUSSION

Patient and public involvement is an integral part of this trial and the key outcome is the qualitative result, which is dependent on obtaining good quality data to advise on participant feasibility, acceptability and preference. This is being addressed by using a standard interview. The development of a pain endpoint is another important outcome and collecting daily measurements is likely to be challenging. Research results will be used to inform design of the Phase 2 trial.

TRIAL REGISTRATION

ISRCTN46078697 18 July 2014.

Increased risk of severe vaso-occlusive episodes after initial acute chest syndrome in children with sickle cell anemia less than 4 years old: Sleep and asthma cohort

Previous studies have shown that the highest incidence of acute chest syndrome (ACS) in sickle cell disease occurs in children <4 years old, and a history of ACS at this age is a risk factor for future ACS episodes. However, the interval associated with the highest risk of subsequent ACS or severe pain is not known. Through this mixed retrospective-prospective observational study, the Sleep and Asthma Cohort, we sought to determine the interval after an initial ACS episode during which the majority of children <4 years old are rehospitalized for ACS or severe pain. The cumulative prevalence of rehospitalization for ACS or severe pain within 6 months, 1 years, and 2 years was calculated for children with an initial ACS episode <4 years old and compared to children with an initial ACS episode ≥4 years old. A total of 44.8% and 55.2% of participants had an initial ACS episode <4 years and ≥4 years old (Range: 4-17.7 years), respectively. At 1 year following the initial ACS episode, children <4 years old had a significantly higher cumulative prevalence of rehospitalizations for ACS or pain as compared to children ≥4 years of age, 62.5 and 39.1%, respectively (P = 0.009). After initial ACS episodes, the majority of children <4 years old will be rehospitalized for ACS or severe pain within one year, suggesting the need for a therapeutic intervention for this high-risk group.