Small airway dysfunction as predictor and marker for clinical response to biological therapy in severe eosinophilic asthma: a longitudinal observational study

Elevated mepolizumab levels in patients with severe asthma responsive to 1 year's mepolizumab treatment

Background

Asthma involves variable airflow limitation and persistent airway inflammation. Eosinophilic asthma, characterized by cytokine-mediated type 2 inflammation, is generally treated with inhaled corticosteroids. However, patients with severe asthma may require biologics, such as mepolizumab, which targets IL-5 and can manage uncontrolled eosinophilic asthma.

Objective

We investigated the relationship between serum mepolizumab concentrations and treatment response in patients with severe asthma.

Methods

Patients with mepolizumab-treated severe asthma were enrolled onto this prospective cohort study. Baseline assessments were conducted and repeated at 3, 6, and 12 months. Those with response were categorized on the basis of improvements in asthma control test score, lung function, and asthma exacerbations. We quantified the serum concentration of mepolizumab at 3, 6, and 12 months after treatment by liquid chromatography coupled with tandem mass spectrometry.

Results

Twenty-five adult patients aged 20 years and older with severe asthma were included in the analysis. Serum mepolizumab concentrations significantly increased at 6 and 12 months compared with those at 3 months, particularly in those with disease that responded to therapy. Furthermore, the relative change in mepolizumab concentration was significantly higher in those with response than in those with no response. Body size parameters were negatively correlated with mepolizumab concentration. In those with response, there were inverse correlations between mepolizumab concentration and baseline body size parameters.

Conclusions

The study observed a yearlong increase in mepolizumab concentrations, particularly in those with response, indicating a potential mepolizumab surplus. Correlations between mepolizumab concentrations and baseline characteristics suggested differing mepolizumab requirements between those with response and those with no response. Further research is needed to validate these findings and optimize treatment strategies for patients with severe asthma.

Skin Surface Lipid-RNA Profile Obtained from Patients with Severe Asthma After Benralizumab Treatment

Background

Examining human coding and non-coding RNAs present in skin surface lipids (SSL-RNAs) offers a promising approach to understanding the physiological state of the skin. Benralizumab treatment can reduce exacerbations and improve symptom control and quality of life in patients with severe eosinophilic asthma. Although this treatment effectively depletes peripheral blood eosinophils, the impact of benralizumab on SSL-RNA remains completely unknown.

Objective

To investigate the effects of benralizumab treatment on SSL-RNA profiles in patients with severe asthma.

Methods

Skin samples were non-invasively collected from patients before and after one year of benralizumab treatment. Sixteen patients were enrolled, but the SSL-RNA analysis was only feasible for five patients due to collection challenges, mainly in female participants.

Results

Following benralizumab treatment, asthma symptoms, exacerbation rates, and lung function parameters improved. Peripheral blood eosinophils were completely depleted and serum eotaxin-1 levels increased. SSL-RNA analysis revealed differential expression of 134 genes, with significant downregulation of immune-related pathways and genes associated with neutrophilic inflammation.

Conclusion

These findings suggest a suppression of both type 2 and non-type 2 inflammation in response to benralizumab treatment, with potential implications for asthma management. However, the limitations of the study include a small sample size and challenges in sebum collection, particularly among female participants. Although the noninvasive nature of this sampling method makes it attractive for both research and clinical applications, additional studies are needed to fully investigate the potential of SSL-RNA analysis as a noninvasive biomarker to assess treatment response in asthma.

Impact of Dupilumab on Skin Surface Lipid-RNA Profile in Severe Asthmatic Patients

The analysis of skin surface lipid-RNAs (SSL-RNAs) provides a non-invasive method for understanding the molecular pathology of atopic dermatitis (AD), but its relevance to asthma remains uncertain. Although dupilumab, a biologic drug approved for both asthma and AD, has shown efficacy in improving symptoms for both conditions, its impact on SSL-RNAs is unclear. This study aimed to investigate the impact of dupilumab treatment on SSL-RNA profiles in patients with severe asthma. An SSL-RNA analysis was performed before and after administering dupilumab to asthma patients requiring this intervention. Skin samples were collected non-invasively from patients before and after one year of dupilumab treatment. Although 26 patients were enrolled, an SSL-RNA analysis was feasible in only 7 due to collection challenges. After dupilumab treatment, improvements were observed in asthma symptoms, exacerbation rates, and lung function parameters. Serum levels of total IgE and periostin decreased. The SSL-RNA analysis revealed the differential expression of 218 genes, indicating significant down-regulation of immune responses, particularly those associated with type 2 inflammation, suggesting potential improvement in epithelial barrier function. Dupilumab treatment may not only impact type 2 inflammation but also facilitate the normalization of the skin. Further studies are necessary to fully explore the potential of SSL-RNA analysis as a non-invasive biomarker for evaluating treatment response in asthma.

Real-World Efficacy of Biological Therapies in Severe Asthma: A Focus on Small Airways

Background: Severe asthma is a challenging condition that often resists traditional treatments and requires high-dose inhaled corticosteroids and other controllers to manage uncontrolled symptoms. Recent advances include the use of biologic agents targeting specific inflammation pathways, which have improved symptom control and quality of life, although their effects on small airways remain less understood. Methods: This prospective observational study, conducted at Tor Vergata University Hospital in Rome from July 2021 to March 2024, aims to evaluate the efficacy of treatments in patients with uncontrolled severe asthma. It involves baseline assessments and follow-ups at 1 and 3 months post-biological therapy initiation, focusing on both spirometric and non-spirometric (oscillometry) measurements of the small airways to provide a comprehensive evaluation of respiratory function. Results: This study, conducted from July 2021 to March 2024, enrolled 40 patients with severe asthma, ultimately analyzing data from 31 participants who underwent biological therapy. The results showed significant improvements in asthma symptoms, the ACT scores increased significantly from visit 1 to visit 2 (p = 0.00008) and from visit 1 to visit 3 (p = 0.00047), and pulmonary function tests, with notable increases in FEV1 (from visit 1 (74.97 ± 23.43%) to visit 2 (82.96 ± 26.57%, p = 0.041) and to visit 3 (88.89 ± 31.41%, p = 0.003)) and quality of life scores, and substantial reductions in specific airway resistance and small airway dysfunction markers (the PEF, %pr post-BD showed significant improvement from visit 1 to visit 3 (p = 0.012)). However, oscillometric measurements showed no significant changes post-therapy. Conclusions: The study concluded that there was an improvement in the small airways measured by non-oscillometric values, without significant improvements in oscillometric parameters. Additionally, a significant improvement in symptoms was observed after the first month of therapy. There was also a significant increase in respiratory function after one to three months of therapy.

Small airway dysfunction links asthma exacerbations with asthma control and health-related quality of life

BACKGROUND

Small airway dysfunction not only affects asthma control, but also has adverse effects on the psychological and/or social activities of asthma patients. However, few long-term observational studies have explored the complex relationship between small airway dysfunction and asthma control and health-related quality of life in patients with asthma exacerbations.

METHODS

The study recruited 223 patients with exacerbations of asthma (i.e. those with at least one asthma attack over the past year) and 228 patients without exacerbations of asthma (i.e. those without asthma attacks over the past year). We evaluated SAD in patients with asthma exacerbations using impulse oscillometry method. At each evaluation time point within one year of follow-up, the attending physician conducts a case investigation of the patients. We analyzed the correlation between SAD and general characteristics (age, obesity, smoking history), type 2 inflammation (blood eosinophils, exhaled nitric oxide), FEV1, as well as asthma control (ACT) and health-related quality of life (mini-AQLQ) in patients with asthma exacerbations, and constructed a structural equation model to evaluate the causality of these clinical variables.

RESULTS

The SAD prevalence in patients with asthma exacerbation is as high as 75%. SAD is connected with poor asthma control and poor health-related quality of life. The structural equation model indicates that age, obesity, FeNO, and FEV1 are independent predictive factors of SAD. SAD is the main determinant factor of asthma control, which in turn affected health-related quality of life. FEV1 and age directly affect asthma control and affect health-related quality of life through asthma control. In addition, there is a bidirectional relationship between FEV1 and small airway dysfunction and between asthma control and health-related quality of life.

CONCLUSIONS

Small airways are involved from an early stage in asthma. Abnormal function of the small airways can significantly increase airway resistance in asthma patients, while worsening their clinical symptoms. In addition, aging is also a key risk factor for asthma control. Especially, small airway dysfunction links asthma control with health-related quality of life.

Identification and treatment of persistent small airway dysfunction in paediatric patients with asthma: a retrospective cohort study

BACKGROUND

Asthma is a common respiratory disease. In asthma, the small airways have more intensive inflammation and prominent airway remodelling, compared to the central airways. We aimed to investigate the predictive value of risk factors and the fractional concentration of exhaled nitric oxide (FeNO) for persistent small airway dysfunction (p-SAD), and compare the effects of different treatment modalities.

METHODS

This retrospective cohort study included 248 children with asthma (aged 4-11 years). Binary logistic regression was used to analyse the risk factors for p-SAD. Correlations among FEV1/FVC, small airway function parameters, and FeNO levels in patients with asthma were analysed using Spearman's rank correlation. The receiver operating characteristic curve and the Delong test were used to analyse the predictive value of FeNO for p-SAD. Differences in the treatment effects of inhaled corticosteroids (ICS) and ICS with a long-acting beta-agonist (ICS/LABA) on p-SAD were analysed using Fisher's exact test.

RESULTS

Asthmatic children with older age of receiving the regular treatment (OR 1.782, 95% CI 1.082-2.935), with younger age at the time of onset of suspected asthma symptoms (OR 0.602, 95% CI 0.365-0.993), with longer duration of using ICS or ICS/LABA (OR 1.642, 95% CI 1.170-2.305) and with worse asthma control (OR 3.893, 95% CI 1.699-8.922) had increased risk for p-SAD. Significant negative correlations of small airway function parameters with FeNO at a 200 mL/s flow rate (FeNO200), and the concentration of nitric oxide in the alveolar or acinar region (CaNO) were observed. The areas under the curve of FeNO200 (cut-off:10.5ppb), CaNO (cut-off:5.1ppb), and FeNO200 combined with CaNO were 0.743, 0.697, and 0.750, respectively, for asthma with p-SAD. After using ICS or ICS/LABA, switching to ICS/LABA was easier than continuing with ICS to improve small airway dysfunction (SAD) in the 8th month.

CONCLUSIONS

Paediatric asthma with p-SAD is associated with older age at receiving regular treatment, younger age at the time of onset of suspected asthma symptoms, longer duration of using ICS or ICS/LABA, worse asthma control, and higher FeNO200 and CaNO levels, all of which can be combined with small airway function indicators to distinguish p-SAD from asthma. ICS/LABA improves SAD better than ICS alone.

Small airways in asthma: From inflammation and pathophysiology to treatment response

Small airways are characterized as those with an inner diameter less than 2 mm and constitute a major site of pathology and inflammation in asthma disease. It is estimated that small airways dysfunction may occur before the emergence of noticeable symptoms, spirometric abnormalities and imaging findings, thus characterizing them as "the quiet or silent zone" of the lungs. Despite their importance, measuring and quantifying small airways dysfunction presents a considerable challenge due to their inaccessibility in usual functional measurements, primarily due to their size and peripheral localization. Several pulmonary function tests have been proposed for the assessment of the small airways, including impulse oscillometry, nitrogen washout, body plethysmography, as well as imaging methods. Nevertheless, none of these methods has been established as the definitive "gold standard," thus, a combination of them should be used for an effective assessment of the small airways. Widely used asthma treatments seem to also affect several parameters of the small airways. Emerging biologic treatments show promising results in reducing small airways inflammation and remodelling, providing evidence for potential alterations in the disease's progression and outcomes. These novel therapies have implications not only in the clinical aspects of asthma but also in its inflammatory and functional aspects.

Pretreatment circulating MAIT cells, neutrophils, and periostin predicted the real-world response after 1-year mepolizumab treatment in asthmatics

BACKGROUND

Mepolizumab treatment improves symptom control and quality of life and reduces exacerbations in patients with severe eosinophilic asthma. However, biomarkers that predict therapeutic effectiveness must be determined for use in precision medicine. Herein, we elucidated the dynamics of various parameters before and after treatment as well as patient characteristics predictive of clinical responsiveness to mepolizumab after 1-year treatment.

METHODS

Twenty-seven patients with severe asthma were treated with mepolizumab for one year. Asthma control test scores, pulmonary function tests, fractional exhaled nitric oxide levels, and blood samples were evaluated. Additionally, we explored the role of CD69-positive mucosal-associated invariant T (MAIT) cells as a candidate biomarker for predicting treatment effectiveness by evaluating an OVA-induced asthma murine model using MR1 knockout mice, where MAIT cells were absent.

RESULTS

The frequencies of CD69-positive group 1 innate lymphoid cells, group 3 innate lymphoid cells, natural killer cells, and MAIT cells decreased after mepolizumab treatment. The frequency of CD69-positive MAIT cells and neutrophils was lower and serum periostin levels were higher in responders than in non-responders. In the OVA-induced asthma murine model, CD69-positive MAIT cell count in the whole mouse lung was significantly higher than that in the control mice. Moreover, OVA-induced eosinophilic airway inflammation was exacerbated in the MAIT cell-deficient MR1 knockout mice.

CONCLUSIONS

This study shows that circulating CD69-positive MAIT cells, neutrophils, and serum periostin might predict the real-world response after 1-year mepolizumab treatment. Furthermore, MAIT cells potentially have a protective role against type 2 airway inflammation.

Long-Term Efficacy and Safety Among Patients With Severe Eosinophilic Asthma Treated With Mepolizumab and Its Effect on Small Airways

BACKGROUND

The major problem at the Cleveland Allergy and Asthma Center was the need for additional therapy for severe eosinophilic asthma patients who were steroid-dependent or required frequent bursts of prednisone.

OBJECTIVES

The objectives of this study were to determine the efficacy of monthly mepolizumab (MP) injections up to 6½ years using Asthma Control Quesitonnaire-7 (ACQ-7), forced expiratory volume in 1 second (FEV1), forced expiratory flow at 25% to 75% (FEF25%-75%) overall and among super-responders, and to understand whether FEF25%-75% is an effective parameter to evaluate MP efficacy.

METHODS

We reviewed the charts of 67 patients with severe eosinophilic asthma and compared the results between 47 super-responders and the rest of the cohort regarding ACQ-6, ACQ-7, eosinophils, FEV1, and FEF25%-75%. The groups of super-responders and all other patients were described with respect to initial and current values of the study end points using medians and 25th and 75th percentiles. Changes from the initial to the current values in the study end points were measured using percent changes. The Wilcoxon signed rank test was used within each group to test the null hypothesis of 0 median percent change.

RESULTS

After 6½ years, there were no significant changes in FEV1. The FEF25%-75%, had a significant median percent increase of 40% among the super-responders (P < .001), which was substantially higher (P = .026) than the median percent increase of 13.8% observed among all other patients.

CONCLUSIONS

The use of MP up to 6½ years was safe and effective, with significant changes to ACQ-7 and FEF25%-75% associated with MP treatment, but not the FEV1. A higher magnitude of changes was observed among super-responders than the rest of the cohort. Changes in FEF25%-75% were more meaningful than changes in FEV1 in evaluating pulmonary function responsiveness of severe eosinophilic asthma to MP.

Window of opportunity for respiratory oscillometry: A review of recent research

Oscillometry has been around for almost 70 years, but there are still many unknowns. The test is performed during tidal breathing and is therefore free from patient-dependent factors that could influence the results. The Forced Oscillation Technique (FOT), which requires minimal patient cooperation, is gaining ground, particularly with elderly patients and children. In pulmonology, it is a valuable tool for assessing obstructive conditions (with a distinction between central and peripheral obstruction) and restrictive disorders (intrapulmonary and extrapulmonary). Its sensitivity allows the assessment of bronchodilator and bronchoconstrictor responses. Different lung diseases show different patterns of changes in FOT, especially studied in asthma and chronic obstructive pulmonary disease. Because of these differences, many studies have analysed the usefulness of this technique in different areas of medicine. In this paper, the authors would like to present the basics of oscillometry with the areas of its most recent clinical applications.

Definitions of non-response and response to biological therapy for severe asthma: a systematic review

Background

Biologics have proven efficacy for patients with severe asthma but there is lack of consensus on defining response. We systematically reviewed and appraised methodologically developed, defined and evaluated definitions of non-response and response to biologics for severe asthma.

Methods

We searched four bibliographic databases from inception to 15 March 2021. Two reviewers screened references, extracted data, and assessed methodological quality of development, measurement properties of outcome measures and definitions of response based on COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN). A modified GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach and narrative synthesis were undertaken.

Results

13 studies reported three composite outcome measures, three asthma symptoms measures, one asthma control measure and one quality of life measure. Only four measures were developed with patient input; none were composite measures. Studies utilised 17 definitions of response: 10 out of 17 (58.8%) were based on minimal clinically important difference (MCID) or minimal important difference (MID) and 16 out of 17 (94.1%) had high-quality evidence. Results were limited by poor methodology for the development process and incomplete reporting of psychometric properties. Most measures rated "very low" to "low" for quality of measurement properties and none met all quality standards.

Conclusions

This is the first review to synthesise evidence about definitions of response to biologics for severe asthma. While high-quality definitions are available, most are MCIDs or MIDs, which may be insufficient to justify continuation of biologics in terms of cost-effectiveness. There remains an unmet need for universally accepted, patient-centred, composite definitions to aid clinical decision making and comparability of responses to biologics.

Comparative assessment of small airway dysfunction by impulse oscillometry and spirometry in chronic obstructive pulmonary disease and asthma with and without fixed airflow obstruction

Background

Small airways play a major role in the pathogenesis and prognosis of chronic obstructive pulmonary disease (COPD) and asthma. More data on small airway dysfunction (SAD) using spirometry and impulse oscillometry (IOS) in these populations are required. The objective of this study was to compare the two methods, spirometry and IOS, for SAD detection and its prevalence defined by spirometry and IOS in subjects with COPD and asthma with and without fixed airflow obstruction (FAO).

Design

This is a cross-sectional study.

Methods

Spirometric and IOS parameters were compared across four groups (COPD, asthma with FAO, asthma without FAO, and healthy subjects). SAD defined by spirometry and IOS criteria were compared.

Results

A total of 262 subjects (67 COPD, 55 asthma with FAO, 101 asthma without FAO, and 39 healthy controls) were included. The prevalence of SAD defined by using IOS and spirometry criteria was significantly higher in patients with COPD (62.7 and 95.5%), asthma with FAO (63.6 and 98.2%), and asthma without FAO (38.6 and 19.8%) in comparison with healthy control (7.7 and 2.6%). IOS is more sensitive than spirometry in the detection of SAD in asthma without FAO (38.6% vs. 19.8%, p = 0.003) However, in subjects with FAO (COPD and asthma with FAO), spirometry is more sensitive than IOS to detect SAD (95.5% vs. 62.7%, p < 0.001 and 98.2% vs. 63.6%, p < 0.001, respectively).

Conclusion

Small airway dysfunction was significantly detected in COPD and asthma with and without FAO. Although IOS shows more sensitivity than spirometry in the detection of SAD in asthma without FAO, spirometry is more sensitive than IOS in patients with FAO including COPD and asthma with FAO.

Assessing the prognostic value of respiratory oscillometry in patients with difficult-to-treat asthma

Respiratory oscillometry is widely explored in asthma management; however, there is currently no consensus on its routine work-up in patients with difficult-to-treat asthma. We conducted a retrospective, cross-sectional study involving patients with difficult-to-treat asthma at Asia University Hospital between January 2017 and October 2020. We aimed to correlate clinical significance of respiratory oscillometry and asthma treatment outcomes including symptoms control and exacerbation in patients with difficult-to-treat asthma. Among the 69 patients enrolled in the study, a total of 26.1% of the patients experienced at least one severe or two moderate exacerbations. Patients with ACT < 20 presented a higher prevalence of higher frequency-dependent resistance (FDR; the difference in resistance at 5 Hz and 20 Hz) and frequency of resonance (Fres) than those with ACT ≥ 20. In the multivariable analysis, comorbidities, COPD or allergic rhinitis, and FDR were independent factors in increasing the odds ratio in poorly controlled asthma. (FDR ≥ 0.10 vs. < 0.10, adjusted ORR = 5.05, P = 0.037) There was a higher proportion of frequent exacerbations in patients with higher FDR (FDR ≥ 0.10 vs. < 0.10 = 30.0%:20.7%), but IOS parameters failed to predict frequent exacerbations on further analysis. FDR may be a potential clinical parameter for predicting symptom control in patients with difficult-to-treat asthma.

Super-Responders to Biologic Treatment in Type 2-High Severe Asthma: Passing Fad or a Meaningful Phenotype?

Defining super-response to biologic treatment is a major concern in severe asthma. Although many definitions have been proposed, there is still a gap between the clinical perception of the super-response and a standardized classification. The current definition of super-response mainly relies on several clinical features, while many aspects of severe asthma inflammation and lung function are still poorly considered. Furthermore, many criteria of severe asthma super-response overlap with those of the clinical remission, leaving room for possible misclassifications. In this context, identifying the correct trajectory linking these 2 aspects of type 2-high severe asthma could help clinicians to understand which factors can predict a greater response to biologic therapies. In this paper, we review various aspects of super-response assessment, proposing some new criteria for its definition as well as new perspectives on its relationship with severe asthma clinical remission.

Daytime and Nighttime Visual Analog Scales May Be Useful in Assessing Asthma Control Levels Before and After Treatment

PURPOSE

Few questionnaires evaluate daytime and nighttime symptoms separately, although these assessments could contribute to the improvement of disease control levels and prevention of future risks in asthma. The purpose of this retrospective study was to investigate whether daytime and nighttime visual analog scales (VAS) are useful in measuring the perception of symptoms, assessing disease control levels, and evaluating the treatment effects in asthma.

PATIENTS AND METHODS

Self-reporting asthma control tests (ACT) before and after treatment are standardized tests used to determine disease control levels. A multiple regression analysis was performed to determine the correlation between daytime and nighttime VAS and the characteristics of patients before treatment, as well as the changes in VAS and lung functions and fractional exhaled nitrogen oxide after treatment in 55 treatment-naïve symptomatic adult patients with asthma.

RESULTS

Both daytime (r = -0.57, P < 0.0001) and nighttime (r = -0.46, P < 0.0001) VAS correlated well with ACT scores, and there was a correlation between daytime and nighttime VAS (r = 0.33, P = 0.0148) before treatment. In addition, the changes in daytime (r = -0.65, P < 0.0001) and nighttime (r = -0.44, P < 0.0001) VAS were significantly associated with changes in the ACT scores. The multiple regression analysis (β [95% confidence interval]) revealed that improvements in the daytime (-2.33 [-4.55 to -0.11], P = 0.0405) and nighttime (-3.09 [-6.25 to 0.07], P = 0.0505) VAS were associated with an increased forced vital capacity after treatment, although there was no correlation between the VAS and characteristics before treatment.

CONCLUSION

Our study demonstrated that daytime and nighttime VAS were useful in assessing disease control levels and evaluating the treatment effects in asthma.

Monoclonal antibodies targeting small airways: a new perspective for biological therapies in severe asthma

Small airway dysfunction (SAD) in asthma is characterized by the inflammation and narrowing of airways with less of 2 mm in diameter between generations 8 and 23 of the bronchial tree. It is now widely accepted that small airways are involved in the pathogenesis of asthma and are a major determinant of airflow obstruction in this disease. 

In recent years, specialized tests have been developed, such as Impulse Oscillometry (IOS) and Multiple Breath Nitrogen Washout (MBNW) tests, which have been deemed more accurate in detecting SAD than conventional spirometry. Clinical studies show that SAD is associated with more severe bronchial hyperresponsiveness, worse asthma control, and a higher risk of exacerbations. Recent data from a large cohort study showed that the prevalence of SAD in asthma patients increases with asthma severity. Overall, SAD seems to represent a treatable trait, which makes it appealing for asthma control optimization and exacerbation rate reduction, especially in moderate-to-severe asthma.

Biologic agents are now available for the treatment of different severe asthma phenotypes and endotypes. However, the effect of these therapies on SAD remains poorly characterized. Literature showing that biologic agents can also favorably improve small airway function is accumulating. In particular, anti-IL5 agents (mepolizumab and benralizumab) seems to have a greater impact on SAD as compared to other biological agents, but direct comparisons in prospective randomized controlled trials are lacking.

In this mini-review article, we address the latest evidence on the effect of biological therapies on SAD in patients with severe asthma.

Longitudinal Impact of Sputum Inflammatory Phenotypes on Small Airway Dysfunction and Disease Outcomes in Asthma

BACKGROUND

Little is known about the relationship between airway inflammatory phenotypes and some important asthma features such as small airway dysfunction (SAD).

OBJECTIVE

To describe the longitudinal impact of airway inflammatory phenotypes on SAD and asthma outcomes.

METHODS

We measured eosinophil and neutrophil counts in induced sputum at baseline and 1 year later to stratify 197 adult patients with asthma into 4 inflammatory phenotypes. We conducted a comprehensive assessment of lung function using spirometry, body plethysmography, impulse oscillometry, and inert gas single and multiple breath washouts. We compared lung function, asthma severity, exacerbation frequency, and symptom control between the phenotypes. We studied the longitudinal impact of persistent sputum inflammatory phenotypes and the change of sputum cell counts on lung function.

RESULTS

Patients were stratified into eosinophilic (23%, n = 45), neutrophilic (33%, n = 62), mixed granulocytic (22%, n = 43), and paucigranulocytic (24%, n = 47) phenotypes. Patients with eosinophilic and mixed granulocytic asthma had higher rates of airflow obstruction and severe exacerbation as well as poorer symptom control than patients with paucigranulocytic asthma. All SAD measures were worse in patients with eosinophilic and mixed asthma than in those with paucigranulocytic asthma (all P values <.05). Eosinophilic asthma also indicated worse distal airflow obstruction, increased ventilation inhomogeneity (all P values <.05), and higher tendency for severe exacerbation (P = .07) than neutrophilic asthma. Longitudinally, persistent mixed granulocytic asthma was associated with the worst follow-up measures of SAD compared with persistent neutrophilic, persistent paucigranulocytic, or nonpersistent asthma phenotypes. In patients with stable forced expiratory volume in 1 second (FEV1), the mean increase in small airway resistance (R5-20) was greater in patients with persistent mixed granulocytic asthma (+103%) than in patients with persistent neutrophilic (+26%), P = .040, or persistent paucigranulocytic asthma (-41%), P = .028. Multivariate models adjusted for confounders and treatment with inhaled or oral corticosteroids or antieosinophilic biologics indicated that the change of sputum eosinophil rather than neutrophil counts is an independent predictor for the longitudinal change in FEV1, forced expiratory flow at 25% to 75% of forced vital capacity, specific effective airway resistance, residual lung volume, and lung clearance index.

CONCLUSIONS

In asthma, airway eosinophilic inflammation is the main driver of lung function impairment and poor disease outcomes, which might also be aggravated by the coexistence of airway neutrophilia to confer a severe mixed granulocytic asthma phenotype. Persistent airway eosinophilia might be associated with dynamic SAD even in patients with stable FEV1.

Small Airways: The “Silent Zone” of 2021 GINA Report?

Asthma is a chronic disease, affecting approximately 350 million people worldwide. Inflammation and remodeling in asthma involve the large airways, and it is now widely accepted that the small airways (those with an internal diameter <2 mm) are involved in the pathogenesis of asthma and are the major determinant of airflow obstruction in this disease. From a clinical perspective, small airways dysfunction (SAD) is associated with more severe bronchial hyperresponsiveness, worse asthma control and more exacerbations. Unlike the GOLD guidelines which, in their definition, identify COPD as a disease of the small airways, the Global Initiative for Asthma (GINA) guidelines do not refer to the prevalence and role of SAD in asthmatic patients. This decision seems surprising, given the growing body of compelling evidence accumulating pointing out the high prevalence of SAD in asthmatic patients and the importance of SAD in poor asthma control. Furthermore, and remarkably, SAD appears to possess the characteristics of a treatable pulmonary trait, making it certainly appealing for asthma control optimization and exacerbation rate reduction. In this mini-review article, we address the most recent evidence on the role of SAD on asthma control and critically review the possible inclusion of SAD among treatable pulmonary traits in international guidelines on asthma.

Small Airway Dysfunction in Cough Variant Asthma: Prevalence, Clinical, and Pathophysiological Features

Introduction: Small airway dysfunction (SAD) commonly presents in patients with classic asthma, which is associated with airway inflammation, disease severity, and asthma control. However, the prevalence of SAD, its relationship with cough severity and airway inflammation, and its development after antiasthmatic treatment in patients with cough variant asthma (CVA) need to be clarified. This study aimed to investigate the prevalence of SAD and its relationship with clinical and pathophysiological characteristics in patients with CVA and the change in small airway function after antiasthmatic treatment.

Methods: We retrospectively analyzed 120 corticosteroid-naïve patients with CVA who had finished a standard questionnaire and relevant tests in a specialist cough clinic, such as cough visual analog scale (VAS), differential cells in induced sputum, fractional exhaled nitric oxide (FeNO) measurement, spirometry, and airway hyper-responsiveness. Information of 1-year follow-up was recorded in a part of patients who received complete cough relief after 2 months of treatment. SAD was defined as any two parameters of maximal mid-expiratory flow (MMEF)% pred, forced expiratory flow at 50% of forced vital capacity (FEF50%) pred, and forced expiratory flow at 75% of forced vital capacity (FEF75%) pred measuring <65%.

Results: SAD occurred in 73 (60.8%) patients with CVA before treatment. The patients with SAD showed a significantly longer cough duration (24.0 vs. 6.0, p = 0.031), a higher proportion of women (78.1 vs. 59.6%, p = 0.029), older mean age (41.9 vs. 35.4, p = 0.005), and significantly lower forced expiratory volume in 1 s (FEV₁%) pred, FEV₁/FVC, MMEF% pred, FEF50% pred, FEF75% pred, PEF% pred, and PD20 (all p < 0.01) as compared with patients without SAD. There were no significant differences in cough VAS, sputum eosinophils count, FeNO, and TIgE level between patients with SAD and those without SAD. Among 105 patients who completed 2 months of antiasthmatic treatment and repeatedly experienced spirometry measurement, 57 (54.3%) patients still had SAD, despite a significant improvement in cough VAS, sputum eosinophils, FeNO, FEF50% pred, and PEF% pred (all p < 0.01). As compared with patients without SAD, patients with SAD showed no significant differences in the relapse rate (50.0 vs. 41.9%, p = 0.483) and wheeze development rate (10.4 vs. 0%, p = 0.063) during the follow-up.

Conclusions: Small airway dysfunction occurred in over half of patients with CVA and persisted after short-term antiasthmatic treatment, which showed distinctive clinical and pathophysiological features.

Small Airway Dysfunction Measured by Impulse Oscillometry and Fractional Exhaled Nitric Oxide Is Associated With Asthma Control in Children

BACKGROUND

Impulse oscillometry (IOS) and fractional exhaled nitric oxide (FeNO) are sensitive and non-invasive methods to measure airway resistance and inflammation, although there are limited population-based studies using IOS and FeNO to predict asthma control.

OBJECTIVE

This study aimed to investigate the utility of IOS and FeNO for assessing childhood asthma control in terms of small airway dysfunction and airway inflammation.

METHODS

This prospective observational cohort study enrolled 5,018 school children (aged 6-12 years), including 560 asthmatic children and 140 normal participants. FeNO, spirometry, IOS, bronchial dilation test, total IgE, and childhood asthma control test (C-ACT) were measured. FeNO, IOS, spirometry, and C-ACT results were correlated with childhood asthma with and without control.

RESULTS

Uncontrolled asthmatic children had abnormal FeNO, IOS, and spirometric values compared with control subjects (P < 0.05). IOS parameters with R5, R5-R20, X5, Ax, △R5, and FeNO can predict lower C-ACT scales by the areas under receiver operating characteristic curves (AUCs) (0.616, 0.625, 0.609, 0.622, 0.625, and 0.714). A combination of FeNO (>20 ppb) with IOS measure significantly increased the specificity for predicting uncontrolled asthma patients compared with FeNO alone (P < 0.01). A multiple regression model showed that small airway parameter (R5-R20) was the strongest risk factor [OR (95% CI): 87.26 (7.67-993.31)] for uncontrolled asthma patients. Poor control with lower C-ACT scales correlated with high FeNO (r = -0.394), R5 (r = -0.106), and R5-R20 (r = -0.129) in asthmatic children (P < 0.05).

CONCLUSION

A combined use of FeNO and IOS measurements strongly predicts childhood asthma with or without control.

The Relevance of Small Airway Dysfunction in Asthma with Nocturnal Symptoms

Rationale

Small airway dysfunction (SAD) is a frequent feature of asthma that has been linked to disease severity and poor symptom control. However, little is known about the role of SAD in nocturnal asthma.

Objective

To study the association between the severity of SAD and frequency of nocturnal symptoms compared to conventional lung function testing.

Methods

We assessed the frequency of self-reported nocturnal symptoms through the asthma control test. We studied the impact of nocturnal asthma using the Asthma Quality of Life Questionnaire (AQLQ) and the Multidimensional Fatigue Inventory (MFI-20). We assessed the lung function using spirometry, body plethysmography, impulse oscillometry, single and multiple inert gas washout and measured markers of T2-inflammation (blood and sputum eosinophils; fractional exhaled nitric oxide (FeNo)). We stratified the patients according to the presence and frequency of nocturnal asthma.

Results

A total of 166 asthma patients were enrolled in the analysis. Eighty-seven patients (52%) reported to have nocturnal symptoms at least once in the last four weeks. The odds ratio of nocturnal asthma correlated with the severity of all non-spirometric measures of SAD, yet neither with airflow obstruction (FEV1 and FEV/FVC) nor with large airway resistance (R20). Patients with frequent nocturnal asthma (n = 29) had a numerical increase of T2 markers and more severe SAD, as indicated by all non-spirometric measures of SAD (all p-values < 0.05), worse overall asthma control, increased fatigue and reduced quality of life (all p-values < 0.01) compared to patients with infrequent nocturnal asthma (n = 58) or patients without nocturnal asthma (n = 79). We identified 63 patients without airflow obstruction, nearly 43% of them (n = 27) had nocturnal asthma. In this subgroup, only markers of air trapping and ventilation heterogeneity were significantly elevated and correlated with the frequency of nocturnal symptoms: LCI (Spearman’s coefficient = −0.42, p < 0.001), RV% (−0.32, p = 0.02).

Conclusion

SAD is closely associated to asthma with nocturnal symptoms. Spirometry might underestimate the broad spectrum of distal lung function impairments in this population of patients.

Small Airway Dysfunction Links Asthma Severity with Physical Activity and Symptom Control

BACKGROUND

Little is known about the role of small airway dysfunction (SAD) and its complex relation with asthma control and physical activity (PA).

OBJECTIVE

To investigate the interrelations among SAD, risk factors for asthma severity, symptom control, and PA.

METHODS

We assessed SAD by impulse oscillometry and other sophisticated lung function measures including inert gas washout in adults with asthma (mild to moderate, n = 140; severe, n = 128) and 69 healthy controls from the All Age Asthma Cohort. We evaluated SAD prevalence and its interrelation with risk factors for asthma severity (older age, obesity, and smoking), type 2 inflammation (sputum and blood eosinophils, fractional exhaled nitric oxide), systemic inflammation (high-sensitivity C-reactive protein), asthma control (AC), and PA (accelerometer for 1 week). We applied a clinical model based on structural equation modeling that integrated causal pathways among these clinical variables.

RESULTS

The prevalence of SAD ranged from 75% to 90% in patients with severe asthma and from 53% to 64% in mild to moderate asthma. Severe SAD was associated with poor AC and low PA. Structural equation modeling indicated that age, obesity, obesity-related systemic inflammation, T2 inflammation, and smoking are independent predictors of SAD. Small airway dysfunction was the main determinant factor of AC, which in turn affected PA. Obesity affected AC directly and through its contribution to SAD and low PA. In addition, PA had bidirectional associations with obesity, SAD, and AC. Structural equation modeling also indicated interrelations among distal airflow limitation, air trapping, and ventilation heterogeneity.

CONCLUSIONS

Small airway dysfunction is a highly prevalent key feature of asthma that interrelates a spectrum of distal lung function abnormalities with risk factors for asthma severity, asthma control, and physical activity.