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

Stroke prevention in Hispanic children with sickle cell anemia: the SACRED trial

ABSTRACT

Sickle cell anemia (SCA) is recognized globally, but little is known about affected Hispanic populations. In partnership with the Dominican Republic, a Hispanic Caribbean island with a large SCA population, a transcranial Doppler (TCD) screening program provided hydroxyurea to children with conditional velocities. Building local capacity, 10 Dominican medical graduates were certified in TCD examinations and trained in hydroxyurea management. The Stroke Avoidance for Children in REpública Dominicana (SACRED) trial enrolled 283 children with average age of 8.7 ± 3.4 years and 130 (46%) females. At initial screening, treatment-naïve children with conditional velocities (170-199 cm/s) were younger (6.6 ± 2.7 vs 8.9 ± 3.4 years; P = .0002) and more anemic (hemoglobin, 7.4 ± 0.8 vs 8.0 ± 1.2 g/dL; P = .0046) than children with normal screening velocities (<170 cm/s). Among 57 treatment-naïve children receiving 6 months of fixed-dose hydroxyurea at 20 mg/kg per day, average TCD velocities decreased by 20 cm/s, and 61% became normal. Compared with fixed-dose hydroxyurea, dose escalation to maximum tolerated dose (MTD) led to fewer sickle-related events with incidence rate ratio 0.59, 95% confidence intervals 0.36 to 0.98, P = .0420. At MTD, TCD benefits were sustained over 5 years, with 81% reverting to normal and an average TCD velocity decrease of 27 cm/s. Brain magnetic resonance imaging documented substantial baseline parenchymal disease; during treatment, 10% developed new vasculopathy, plus 1 stroke and 1 death. The SACRED trial documents a high burden of cerebrovascular disease among Hispanic children with SCA and demonstrates the feasibility of partnership to establish TCD screening programs, the utility of hydroxyurea to reduce TCD velocities and reduce stroke risk, and sustained benefits of hydroxyurea dose escalation. This trial was registered at www.clinicaltrials.gov as #NCT02769845.

Effects of Air Pollution on Respiratory Events and Pain Crises among Children with Sickle Cell Disease in New York City

Rationale: The disease burden of sickle cell disease (SCD) is highest among U.S. Black and Hispanic populations, which are often disproportionately represented in communities with poor air quality. There are limited data on the effects of air pollution exposure and social environmental factors on health outcomes in children with SCD. Objectives: The objectives of our study were to examine the associations between air pollution exposure and acute respiratory and vaso-occlusive pain crises (VOCs) and to further study the associations when stratifying by asthma status and neighborhood disadvantages. Methods: We conducted a retrospective study, collecting data on outpatient sick and emergency department visits, hospital admissions for respiratory events (i.e., respiratory tract infections, asthma exacerbation, acute chest syndrome), and hospitalizations for VOCs among children with SCD in a tertiary care center in New York City from 2015 to 2018. Modeled data from the New York City Community Air Survey data using home addresses' estimated street-level annual average exposure to air pollution (i.e., black carbon, particulate matter with an aerodynamic diameter ≤2.5 μm, and nitrogen dioxide). The area deprivation index (ADI) continuous national ranking percentile (1-100) was used, representing a composite index for neighborhood-level social disadvantage. We further dichotomized study participants at the upper tertile (high vs. low ADI). Multivariable Poisson regression in generalized estimating equation models were used to estimate relative risks (RRs) after adjusting for potential covariates. Results: A total of 114 children with SCD were included in this study and had between one and four annual repeated measures of annual average air pollutants over a total of 425 visits. Overall, there were no significant associations between air pollution levels and acute respiratory pain crises and VOCs among children with SCD and when stratified by asthma status. We found significant interactions between air pollution levels and the continuous ADI variable on respiratory outpatient and frequent respiratory outpatient/ED visits (P < 0.1). When stratified by high ADI, increased exposure to particulate matter with an aerodynamic diameter ≤2.5 μm was significantly associated with more frequent respiratory outpatient/emergency department visits among children residing in higher ADI neighborhoods (RR [95% confidence interval], 1.13 [1.01, 1.27]; P < 0.05), but not among those in lower ADI neighborhoods. Increased exposure to nitrogen dioxide was associated with more outpatient respiratory events for children in high ADI neighborhoods (RR [95% confidence interval], 2.74 [1.24, 6.08]; P < 0.05) compared with low ADI neighborhoods. Conclusions: Air pollution exposures increased respiratory complications among children with SCD living in deprived neighborhoods.

Role of fractional exhaled nitric oxide in patients with sickle cell disease

INTRODUCTION

Patients with sickle cell disease exhibit different patterns in pulmonary function tests. In particular, there is little evidence on the fractional exhaled nitric oxide (FeNO) test, and its value ranges and its interpretation in these patients have been under debate in recent years.

METHODS

We conduced a cross-sectional, observational and descriptive study between November 2021 and January 2023 including patients aged 6-18 years with sickle cell disease able to perform the FeNO test. We applied the GLI-2012 reference values and the ERS/ATS standards. We defined statistical significance as P < 0.05.

RESULTS

The sample included 43 patients with a median age of 12 years (IQR, 10-15). We did not find an association between significantly elevated FeNO (≥25 ppb) and the diagnosis of asthma (P = 0.37), an obstructive pattern in spirometry (P = 0.67), a positive bronchodilator test (P = 0.53), clinical bronchial hyperreactivity in the context of cold or flu-like symptoms (P = 0.48), cough with exercise (P = 0.42) or nocturnal cough (P = 1.0), but found an association with peripheral eosinophilia (P < 0.01).

CONCLUSIONS

We found no association between FeNO values and the classic features of asthma (clinical or spirometric) in patients with sickle cell disease. Therefore, airway inflammation mechanisms are probably different in these patients.

Predictors of Diffusing Capacity in Children With Sickle Cell Disease: A Longitudinal Study

Background: Gas exchange abnormalities in Sickle Cell Disease (SCD) may represent cardiopulmonary deterioration. Identifying predictors of these abnormalities in children with SCD (C-SCD) may help us understand disease progression and develop informed management decisions. Objectives: To identify pulmonary function tests (PFT) estimates and biomarkers of disease severity that are associated with and predict abnormal diffusing capacity (DLCO) in C-SCD. Methods: We obtained PFT data from 51 C-SCD (median age:12.4 years, male: female = 29:22) (115 observations) and 22 controls (median age:11.1 years, male: female = 8:14), formulated a rank list of DLCO predictors based on machine learning algorithms (XGBoost) or linear mixed-effect models, and compared estimated DLCO to the measured values. Finally, we evaluated the association between measured or estimated DLCO and clinical outcomes, including SCD crises, pulmonary hypertension, and nocturnal desaturation. Results: Hemoglobin-adjusted DLCO (%) and several PFT indices were diminished in C-SCD compared to controls. Both statistical approaches ranked FVC (%), neutrophils (%), and FEF_25-75 (%) as the top three predictors of DLCO. XGBoost had superior performance compared to the linear model. Both measured and estimated DLCO demonstrated a significant association with SCD severity: higher DLCO, estimated by XGBoost, was associated with fewer SCD crises [beta = -0.084 (95%CI: -0.13, -0.033)] and lower TRJV [beta = -0.009 (-0.017, -0.001)], but not with nocturnal desaturation (p = 0.12). Conclusions: In this cohort of C-CSD, DLCO was associated with PFT estimates representing restrictive lung disease (FVC, TLC), airflow obstruction (FEF_25-75, FEV1/FVC, R5), and inflammation (neutrophilia). We used these indices to estimate DLCO, and show association with disease outcomes, underscoring the prediction models' clinical relevance.