Determinants of lung function across childhood in the Severe Asthma Research Program (SARP) 3

BACKGROUND

Children with asthma are at risk for low lung function extending into adulthood, but understanding of clinical predictors is incomplete.

OBJECTIVE

We sought to determine phenotypic factors associated with FEV1 throughout childhood in the Severe Asthma Research Program 3 pediatric cohort.

METHODS

Lung function was measured at baseline and annually. Multivariate linear mixed-effects models were constructed to assess the effect of baseline and time-varying predictors of prebronchodilator FEV1 at each assessment for up to 6 years. All models were adjusted for age, predicted FEV1 by Global Lung Function Initiative reference equations, race, sex, and height. Secondary outcomes included postbronchodilator FEV1 and prebronchodilator FEV1/forced vital capacity.

RESULTS

A total of 862 spirometry assessments were performed for 188 participants. Factors associated with FEV1 include baseline Feno (B, -49 mL/log2 PPB; 95% CI, -92 to -6), response to a characterizing dose of triamcinolone acetonide (B, -8.4 mL/1% change FEV1 posttriamcinolone; 95% CI, -12.3 to -4.5), and maximal bronchodilator reversibility (B, -27 mL/1% change postbronchodilator FEV1; 95% CI, -37 to -16). Annually assessed time-varying factors of age, obesity, and exacerbation frequency predicted FEV1 over time. Notably, there was a significant age and sex interaction. Among girls, there was no exacerbation effect. For boys, however, moderate (1-2) exacerbation frequency in the previous 12 months was associated with -20 mL (95% CI, -39 to -2) FEV1 at each successive year. High exacerbation frequency (≥3) 12 to 24 months before assessment was associated with -34 mL (95% CI, -61 to -7) FEV1 at each successive year.

CONCLUSIONS

In children with severe and nonsevere asthma, several clinically relevant factors predict FEV1 over time. Boys with recurrent exacerbations are at high risk of lower FEV1 through childhood.

Quantitative CT Characteristics of Cluster Phenotypes in the Severe Asthma Research Program Cohorts

Background Clustering key clinical characteristics of participants in the Severe Asthma Research Program (SARP), a large, multicenter prospective observational study of patients with asthma and healthy controls, has led to the identification of novel asthma phenotypes. Purpose To determine whether quantitative CT (qCT) could help distinguish between clinical asthma phenotypes. Materials and Methods A retrospective cross-sectional analysis was conducted with the use of qCT images (maximal bronchodilation at total lung capacity [TLC], or inspiration, and functional residual capacity [FRC], or expiration) from the cluster phenotypes of SARP participants (cluster 1: minimal disease; cluster 2: mild, reversible; cluster 3: obese asthma; cluster 4: severe, reversible; cluster 5: severe, irreversible) enrolled between September 2001 and December 2015. Airway morphometry was performed along standard paths (RB1, RB4, RB10, LB1, and LB10). Corresponding voxels from TLC and FRC images were mapped with use of deformable image registration to characterize disease probability maps (DPMs) of functional small airway disease (fSAD), voxel-level volume changes (Jacobian), and isotropy (anisotropic deformation index [ADI]). The association between cluster assignment and qCT measures was evaluated using linear mixed models. Results A total of 455 participants were evaluated with cluster assignments and CT (mean age ± SD, 42.1 years ± 14.7; 270 women). Airway morphometry had limited ability to help discern between clusters. DPM fSAD was highest in cluster 5 (cluster 1 in SARP III: 19.0% ± 20.6; cluster 2: 18.9% ± 13.3; cluster 3: 24.9% ± 13.1; cluster 4: 24.1% ± 8.4; cluster 5: 38.8% ± 14.4; P < .001). Lower whole-lung Jacobian and ADI values were associated with greater cluster severity. Compared to cluster 1, cluster 5 lung expansion was 31% smaller (Jacobian in SARP III cohort: 2.31 ± 0.6 vs 1.61 ± 0.3, respectively, P < .001) and 34% more isotropic (ADI in SARP III cohort: 0.40 ± 0.1 vs 0.61 ± 0.2, P < .001). Within-lung Jacobian and ADI SDs decreased as severity worsened (Jacobian SD in SARP III cohort: 0.90 ± 0.4 for cluster 1; 0.79 ± 0.3 for cluster 2; 0.62 ± 0.2 for cluster 3; 0.63 ± 0.2 for cluster 4; and 0.41 ± 0.2 for cluster 5; P < .001). Conclusion Quantitative CT assessments of the degree and intraindividual regional variability of lung expansion distinguished between well-established clinical phenotypes among participants with asthma from the Severe Asthma Research Program study. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Verschakelen in this issue.

Endotype of allergic asthma with airway obstruction in urban children

BACKGROUND

Black and Hispanic children growing up in disadvantaged urban neighborhoods have the highest rates of asthma and related morbidity in the United States.

OBJECTIVES

This study sought to identify specific respiratory phenotypes of health and disease in this population, associations with early life exposures, and molecular patterns of gene expression in nasal epithelial cells that underlie clinical disease.

METHODS

The study population consisted of 442 high-risk urban children who had repeated assessments of wheezing, allergen-specific IgE, and lung function through 10 years of age. Phenotypes were identified by developing temporal trajectories for these data, and then compared to early life exposures and patterns of nasal epithelial gene expression at 11 years of age.

RESULTS

Of the 6 identified respiratory phenotypes, a high wheeze, high atopy, low lung function group had the greatest respiratory morbidity. In early life, this group had low exposure to common allergens and high exposure to ergosterol in house dust. While all high-atopy groups were associated with increased expression of a type-2 inflammation gene module in nasal epithelial samples, an epithelium IL-13 response module tracked closely with impaired lung function, and a MUC5AC hypersecretion module was uniquely upregulated in the high wheeze, high atopy, low lung function group. In contrast, a medium wheeze, low atopy group showed altered expression of modules of epithelial integrity, epithelial injury, and antioxidant pathways.

CONCLUSIONS

In the first decade of life, high-risk urban children develop distinct phenotypes of respiratory health versus disease that link early life environmental exposures to childhood allergic sensitization and asthma. Moreover, unique patterns of airway gene expression demonstrate how specific molecular pathways underlie distinct respiratory phenotypes, including allergic and nonallergic asthma.

Clinical significance of the bronchodilator response in children with severe asthma

BACKGROUND

Our objective was to determine those characteristics associated with reversibility of airflow obstruction and response to maximal bronchodilation in children with severe asthma through the Severe Asthma Research Program (SARP).

METHODS

We performed a cross-sectional analysis evaluating children ages 6 to 17 years with nonsevere asthma (NSA) and severe asthma (SA). Participants underwent spirometry before and after 180 µg of albuterol to determine reversibility (≥12% increase in FEV₁ ). Participants were then given escalating doses up to 720 µg of albuterol to determine their maximum reversibility.

RESULTS

We evaluated 230 children (n = 129 SA, n = 101 NSA) from five centers across the United States in the SARP I and II cohorts. SA (odds ratio [OR], 2.08, 95% confidence interval [CI], 1.05-4.13), second-hand smoke exposure (OR, 2.81, 95%CI, 1.23-6.43), and fractional exhaled nitric oxide (FeNO; OR, 1.97, 95%CI, 1.35-2.87) were associated with increased odds of airway reversibility after maximal bronchodilation, while higher prebronchodilator (BD) FEV₁ % predicted (OR, 0.91, 95%CI, 0.88-0.94) was associated with decreased odds. In an analysis using the SARP III cohort (n = 186), blood neutrophils, immunoglobulin E (IgE), and FEV₁ % predicted were significantly associated with BD reversibility. In addition, children with BD response have greater healthcare utilization. BD reversibility was associated with reduced lung function at enrollment and 1-year follow-up though less decline in lung function over 1 year compared to those without reversibility.

CONCLUSIONS

Lung function, that is FEV₁ % predicted, is a predictor of BD response in children with asthma. Additionally, smoke exposure, higher FeNO or IgE level, and low peripheral blood neutrophils are associated with a greater likelihood of BD reversibility. BD response can identify a phenotype of pediatric asthma associated with low lung function and poor asthma control.

Racial disparities in asthma-related health care use in the National Heart, Lung, and Blood Institute's Severe Asthma Research Program

BACKGROUND

Despite advances in asthma care, disparities persist. Black patients are disproportionally affected by asthma and also have poorer outcomes compared with white patients.

OBJECTIVE

We sought to determine associations between black and white patients and asthma-related health care use, accounting for complex relationships.

METHODS

This study was completed as part of the National Heart, Lung, and Blood Institute's Severe Asthma Research Program, a prospective observational cohort. Between November 2012 and February 2015, it enrolled 579 participants 6 years and older with 1 year of observation time and complete data. Inverse probability of treatment weighting was used to balance racial groups with respect to community and family socioeconomic variables and environmental exposure variables. The primary outcome was emergency department (ED) use for asthma. Secondary outcomes included inhaled corticosteroid use, outpatient physician's office visits for asthma, and asthma-related hospitalization.

RESULTS

Black patients had greater odds of ED use over 1 year (odds ratio, 2.19; 95% CI, 1.43-3.35) but also differed in the majority (>50%) of baseline variables measured. After statistical balancing of the racial groups, the difference between black and white patients with respect to ED use no longer reached the level of significance. Instead, in secondary analyses black patients were less likely to see an outpatient physician for asthma management (adjusted odds ratio, 0.57; 95% CI, 0.38-0.85).

CONCLUSIONS

The disparity in ED use was eliminated after consideration of multiple variables. Social and environmental policies and interventions tailored to black populations with a high burden of asthma are critical to reduction (or elimination) of these disparities.

Effects of endogenous sex hormones on lung function and symptom control in adolescents with asthma

BACKGROUND

Although pre-puberty asthma is more prevalent in males, after puberty through middle-age, asthma is more prevalent in females. The surge of sex hormones with puberty might explain this gender switch.

METHODS

To examine the effects of sex hormones on lung function and symptoms with puberty, Tanner stage was assessed in 187 children 6-18 years of age (59% severe) enrolled in the NIH/NHLBI Severe Asthma Research Program (SARP). The effects of circulating sex hormones (n = 68; testosterone, dehydroepiandrosterone sulfate (DHEA-S), estrogen, and progesterone) on lung function and 4 week symptom control (ACQ6) in cross-section were tested by linear regression.

RESULTS

From pre-/early to late puberty, lung function did not change significantly but ACQ6 scores improved in males with severe asthma. By contrast females had lower post-BD FEV₁% and FVC% and worse ACQ6 scores with late puberty assessed by breast development. In males log DHEA-S levels, which increased by Tanner stage, associated positively with pre- and post-BD FEV₁%, pre-BD FVC %, and negatively (improved) with ACQ6. Patients treated with high-dose inhaled corticosteroids had similar levels of circulating DHEA-S. In females, estradiol levels increased by Tanner stage, and associated negatively with pre-BD FEV₁% and FVC %.

CONCLUSIONS

These results support beneficial effects of androgens on lung function and symptom control and weak deleterious effects of estradiol on lung function in children with asthma. Longitudinal data are necessary to confirm these cross-sectional findings and to further elucidate hormonal mechanisms informing sex differences in asthma features with puberty.

TRIAL REGISTRATION

ClinicalTrials.gov registration number: NCT01748175 .

Inflammatory and Comorbid Features of Patients with Severe Asthma and Frequent Exacerbations

RATIONALE

Reducing asthma exacerbation frequency is an important criterion for approval of asthma therapies, but the clinical features of exacerbation-prone asthma (EPA) remain incompletely defined.

OBJECTIVES

To describe the clinical, physiologic, inflammatory, and comorbidity factors associated with EPA.

METHODS

Baseline data from the NHLBI Severe Asthma Research Program (SARP)-3 were analyzed. An exacerbation was defined as a burst of systemic corticosteroids lasting 3 days or more. Patients were classified by their number of exacerbations in the past year: none, few (one to two), or exacerbation prone (≥3). Replication of a multivariable model was performed with data from the SARP-1 + 2 cohort.

MEASUREMENTS AND MAIN RESULTS

Of 709 subjects in the SARP-3 cohort, 294 (41%) had no exacerbations and 173 (24%) were exacerbation prone in the prior year. Several factors normally associated with severity (asthma duration, age, sex, race, and socioeconomic status) did not associate with exacerbation frequency in SARP-3; bronchodilator responsiveness also discriminated exacerbation proneness from asthma severity. In the SARP-3 multivariable model, blood eosinophils, body mass index, and bronchodilator responsiveness were positively associated with exacerbation frequency (rate ratios [95% confidence interval], 1.6 [1.2-2.1] for every log unit of eosinophils, 1.3 [1.1-1.4] for every 10 body mass index units, and 1.2 [1.1-1.4] for every 10% increase in bronchodilatory responsiveness). Chronic sinusitis and gastroesophageal reflux were also associated with exacerbation frequency (1.7 [1.4-2.1] and 1.6 [1.3-2.0]), even after adjustment for multiple factors. These effects were replicated in the SARP-1 + 2 multivariable model.

CONCLUSIONS

EPA may be a distinct susceptibility phenotype with implications for the targeting of exacerbation prevention strategies. Clinical trial registered with www.clinicaltrials.gov (NCT 01760915).

Income is an independent risk factor for worse asthma outcomes

BACKGROUND

Socioeconomic status (SES) is associated with asthma morbidity in observational studies, but the factors underlying this association are uncertain.

OBJECTIVE

We investigated whether 3 SES correlates-low income, low education, and high perceived stress-were independent risk factors for treatment failure and asthma exacerbations in the context of a randomized controlled trial.

METHODS

The effect of low SES (household income of <$50,000/y and household educational level of less than a Bachelor's degree) and high perceived stress (defined as a score of >20 on a perceived stress scale) on asthma morbidity was analyzed in 381 participants by using Poisson regression models. The primary outcome was treatment failure (defined in the trial protocol as a significant clinical or airflow deterioration), and the secondary outcome was asthma exacerbations requiring systemic corticosteroids.

RESULTS

Fifty-four percent of participants had a low income, 40% had a low educational level, and 17% had high perceived stress levels. Even after adjusting for race and other important confounders, participants with lower income had higher rates of both treatment failures (rate ratio, 1.6; 95% CI, 1.1-2.3; P = .03) and exacerbations (rate ratio, 1.9; 95% CI, 1.1-3.3; P = .02). Adherence with inhaled corticosteroids was similarly high for both income categories. Education and perceived stress were not significantly associated with either outcome.

CONCLUSIONS

In the context of a randomized controlled trial, participants with lower income were more likely to experience adverse asthma outcomes independent of education, perceived stress, race, and medication adherence.