Managing Chronic Cough Due to Asthma and NAEB in Adults and Adolescents: CHEST Guideline and Expert Panel Report

Bibliometric Analysis of Cough Variant Asthma from 1993 to 2022

Purpose

Cough variant asthma (CVA) is a chronic inflammatory disease characterized by recurrent coughing, a prevalent cause of chronic cough in children and adults. As a unique form of asthma, researchers have recently become increasingly interested in developing effective diagnostic and treatment methods. Currently, there has been no bibliometric analysis in CVA. Therefore, this study aims to enrich this knowledge network by examining the current development status, research focal points, and emerging trends in this field.

Methods

Articles and reviews on CVA published between 1993 and 2022 were collected from the Web of Science Core Collection (WoSCC) database. Relevant data from the reports were extracted, and collaborative network analysis was performed using CiteSpace and VOSviewer software.

Results

772 articles were included in this study, indicating a significant increase since 2019. The countries with the highest output are China, Japan. The Journal of Asthma and Pulmonary Pharmacology Therapeutics emerged as the most prolific journals in this field. Keyword analysis revealed 22 clusters, highlighting airway inflammation, airway hyperresponsiveness, and eosinophil as the main focus and frontier of research on CVA.

Conclusion

From the visual analysis results, the research of CVA is still in the development stage, and there is no unified definition of pathogenesis, diagnostic criteria and treatment strategies. Therefore, researchers and teams should actively carry out cross-institutional and cross-regional cooperation, expand cooperation areas, and carry out high-quality clinical research in the future.

Clinical efficacy of montelukast sodium combination therapy for cough variant asthma in children: A meta-analysis

This meta-analysis aims to assess the clinical effectiveness of combination therapy with montelukast sodium for the treatment of cough variant asthma (CVA) in children, intending to provide clinical evidence and data to guide the selection of clinical therapy. A literature review was conducted using numerous databases, including China National Knowledge Infrastructure (CNKI), Wanfang database, Embase, PubMed, and Web of Science, from inception to December 2023. Trials meeting the criteria for the combined treatment of montelukast sodium for CVA in children were included. Stata 16.0 software was utilized for meta-analysis. The combined treatment group received montelukast sodium in addition to the control group, while the control group received budesonide, fluticasone propionate, salmeterol-fluticasone, or ketotifen alone. This investigation included 18 papers. All subjects were from the Chinese population. Compared to the control group, the combined treatment group demonstrated a higher effective rate (relative ratio [RR] = 1.23, 95% confidence interval [CI]: 1.18-1.29, p < .001), but no difference in the incidence of adverse reactions (RR = 0.65, 95% CI: 0.42-1.02, p = .060) after treatment. Moreover, the peak expiratory flow (PEF) (SMD = 1.69, 95% CI: 1.09-2.30, p < .001), forced vital capacity (FVC) (SMD = 1.67, 95% CI: 0.94-2.39, p < .001), forced expiratory volume in 1 s (FEV1) (SMD = 1.74, 95% CI: 1.09-2.40, p < .001), and FEV1/FVC (SMD = 1.84, 95% CI: 0.41-3.28, p = .012) were significantly higher in the combined treatment group than in the control group after treatment. Compared with the control group, the levels of tumor necrosis factor-α (SMD = -2.38, 95% CI: -3.22 to -1.55, p < .001), IL-4 (SMD = -2.65, 95% CI: -3.26 to -2.04, p < .001), and IgE (SMD = -2.98, 95% CI: -3.24 to -2.72, p < .001) were significantly lower in the combined treatment group after treatment. The combined use of montelukast sodium in the treatment of pediatric CVA in China is associated with a significant clinical effect, making it a reasonable therapeutic approach.

Alveolar nitric oxide concentration plays an important role in identifying cough variant asthma and assessing asthma control in children

OBJECTIVE

To study the value of alveolar nitric oxide concentration (CaNO) in the identification and disease control of cough variant asthma.

METHODS

A retrospective study was conducted on cough variant asthma (CVA-Group), nonasthmatic cough (NAC-Group) and healthy control children (C-Group) aged 5-12 years. The exhaled nitric oxide and spirometry test results of the three groups were collected and compared.

RESULTS

A total of 410 children were included in this study, including 190 in the CVA-Group, 183 in the NAC-Group, and 37 in the C-Group. The CaNO values of the CVA-Group [11.40 ppb (8.48-14.25)] were significantly higher than those of the NAC-Group and C-Group (all p values <.05). The MMEF %pred values of the CVA-Group [63.65 (56.28-73.58)] were significantly lower than those of the NAC-Group and C-Group (all p values <.05). FeNO50, JawNO and other spirometry indices (FVC %pred, FEV1%pred, FEV1/FVC %pred) showed no significant difference among the three groups. ROC curve analysis showed that the optimal cutoff point value of CaNO was 9.45 ppb, corresponding to 0.816 sensitivity and 0.736 specificity. Spearman correlation analysis showed a significant negative correlation between the CaNO measurement and CVA control score.

CONCLUSIONS

CaNO can not only help identify CVA early in children aged 5-12 years with chronic cough but is also significantly negatively correlated with the CVA control score.

Knowledge, attitude, and practice of healthcare providers on chronic refractory cough: A cross-sectional study

Objective

Previous studies from outside China showed that the knowledge, attitudes, and practice (KAP) of chronic refractory cough (CRC) was moderate among physicians. This study examined the KAP toward CRC in Chinese healthcare providers.

Methods

This single-center cross-sectional study was conducted at The Sixth Affiliated Hospital of Nantong University, Yancheng Third People's Hospital, from July 2022 to January 2023 and enrolled healthcare providers. The demographic characteristics and KAP scores were collected using a questionnaire (Cronbach's α = 0.934) developed based on CRC guidelines.

Results

The study included 539 healthcare providers. The mean knowledge score was 8.27 ± 2.37 (maximum of 14, 59.07%), indicating poor knowledge. The highest rates of inaccuracies pertained to knowledge about the definition of chronic cough, empirical treatment methods, and potential risks of different treatments, suggesting a need for unified training in all aspects of CRC for medical staff. The mean attitude score was 49.74 ± 63.63 (maximum of 60, 82.90%), indicating favorable attitudes. Most healthcare providers believed that CRC affects normal work and life and that it would be necessary to provide more help to patients from the perspectives of drug treatment and psychological counseling. The mean practice score was 23.20 ± 6.28 (maximum of 35, 66.29%), indicating poor practice.

Conclusion

This study suggests that healthcare providers in Yancheng have poor knowledge, favorable attitudes, and poor practice of CRC. This study provides points that should be targeted in future training and continuing education activities.

Efficacy and safety of montelukast adjuvant therapy in adults with cough variant asthma: A systematic review and meta-analysis

BACKGROUND

Montelukast is a highly selective and specific cysteinyl leukotriene receptor antagonist used in the treatment of asthma. Whether montelukast as adjuvant therapy can significantly and safely treat adults with cough variant asthma (CVA) remains inconclusive.

AIMS

This meta-analysis systematically evaluated the efficacy and safety of montelukast as an adjuvant treatment for adults with CVA.

MATERIALS AND METHODS

Randomized controlled trials (RCTs) on montelukast combined with inhaled corticosteroids (ICS) and long-acting β2 agonists (LABAs) to treat CVA in adults, from inception to March 6, 2023, were retrieved from the CNKI, Wanfang, VIP, CBM, PubMed, Embase, Cochrane Library, and Web of Science databases and Clinical Trials website. Review Manager (version 5.4) and Stata (version 15.0) were used to conduct the meta-analysis.

RESULTS

A total of 15 RCTs were ultimately included in the meta-analysis. It was established that montelukast as adjuvant therapy raised the total effective rate (RR = 1.20, 95% confidence interval [CI] [1.13, 1.27], P < 0.01) and improved the FEV1% (SMD = 0.91, 95% CI [0.40, 1.41], P < 0.01), PEF% (SMD = 0.63, 95% CI [0.38, 0.88], P < 0.01), FEV1 (SMD = 1.15, 95% CI [0.53, 1.77], P < 0.01), PEF (SMD = 0.64, 95% CI [0.42, 0.86], P < 0.01), and FEV1/FVC% (SMD = 0.76, 95% CI [0.51, 1.01], P < 0.01) and reduced the recurrence rate (RR = 0.28, 95% CI [0.15, 0.53], P < 0.01). The incidence of adverse reactions was higher in the montelukast auxiliary group compared to the control group but with no statistical difference (RR = 1.32, 95% CI [0.89, 1.96], P = 0.17).

CONCLUSION

Existing evidence indicated that the use of montelukast as an adjuvant therapy had therapeutic efficacy superior to ICS + LABA alone for the treatment of adult patients with CVA. However, further research is needed, especially a combination of high-quality long-term prospective studies and carefully designed RCTs.

Diagnostic accuracy of blood eosinophils in comparison to other common biomarkers for identifying sputum eosinophilia in patients with chronic cough

Background

Sputum eosinophilia is a treatable trait for chronic cough. It is currently not clear whether the blood eosinophil counts could be used to identify sputum eosinophilia in patients with chronic cough. This study aimed to evaluate the diagnostic accuracy of blood eosinophils in comparison to other common type 2 biomarkers for identifying sputum eosinophilia in patients with chronic cough.

Methods

In this prospective study, a total of 658 patients with chronic cough were enrolled. Induced-sputum test, routine blood test, total immunoglobulin E (TIgE), and fractional exhaled nitric oxide (FeNO) level were measured. The percentage of sputum eosinophils (Eos%) ≥ 2.5% was defined as sputum eosinophilia. The area under the curve (AUC) of blood eosinophil counts, TIgE, and FeNO alone or in combination for predicting sputum eosinophilia were analyzed.

Results

The AUC of blood eosinophil counts for predicting sputum eosinophilia in chronic cough patients was moderate [0.826 (0.767-0.885)], as compared to that of FeNO [0.784 (0.720-0.849), P = 0.280] and TIgE [0.686 (0.613-0.760), P = 0.001]. When combining blood eosinophil counts and FeNO for detecting sputum eosinophilia, a significantly larger AUC [0.868 (0.814-0.923), with a sensitivity of 84.2% and a specificity of 82.8%] was yielded, as compared to each single marker alone (all P < 0.05).

Conclusions

Blood eosinophil counts have a moderate diagnostic value for identifying sputum eosinophilia in patients with chronic cough, while a combination of blood eosinophil counts and FeNO measurement can provide additional predictive value.

Association of lower plasma citric acid with prolonged cough: the Nagahama study

Little is known about the association of prolonged cough, a common and troublesome symptom, with metabolic pathways. We aimed to clarify this association using data from the Nagahama cohort, a prospective study of participants from the general population. Self-report questionnaires on prolonged cough were collected at baseline and 5-year follow-up assessments. Blood tests at follow-up were used for gas chromatography-mass spectrometry-based metabolomics. The association between metabolites and prolonged cough was examined using the partial least squares discriminant analysis and multiple regression analysis. Among the 7432 participants, 632 had newly developed prolonged cough at follow-up, which was defined as "new-onset prolonged cough". Low plasma citric acid was significantly associated with new-onset prolonged cough, even after the adjustment of confounding factors including the presence of asthma, upper airway cough syndrome (UACS), and gastroesophageal reflux disease (GERD). A similar association was observed for isocitric acid, 3-hydroxybutyric acid, and 3-hydroxyisobutyric acid. The analysis of these four metabolites revealed that citric acid had the strongest association with new-onset prolonged cough. This significant association remained even when the analysis was confined to participants with UACS or GERD at baseline or follow-up, and these associations were also observed in participants (n = 976) who had prolonged cough at follow-up regardless of baseline status. In conclusion, low blood citric acid may be associated with prolonged cough.

Fractional nitric oxide measurement in exhaled air (FeNO): perspectives in the management of respiratory diseases

Exhaled nitric oxide (NO) production, upregulated by inflammatory cytokines and mediators in central and peripheral airways, can be easily and non-invasively detected in exhaled air in asthma and other respiratory conditions as a promising tool for disease monitoring. The American Thoracic Society and European Respiratory Society released recommendations that standardize the measurement of the fractional exhaled NO (FeNO). In asthma, increased FeNO reflects eosinophilic-mediated inflammatory pathways and, as a biomarker of T2 inflammation can be used to identify asthma T2 phenotype. In this setting its measurement has shown to be an important tool especially in the diagnostic process, in the assessment and evaluation of poor adherence or predicting positive response to inhaled corticosteroids treatment, in phenotyping severe asthma patients and as a biomarker to predict the response to biologic treatments. The discovery of the role of NO in the pathogenesis of different diseases affecting the airways and the possibility to estimate the predominant site of increased NO production has provided new insight on its regulatory role in the airways, making it suitable for a potential extended use in clinical practice for different pulmonary diseases, even though its role remains less clear than in asthma. Monitoring FeNO in pulmonary obstructive lung diseases including chronic bronchitis and emphysema, interstitial lung diseases, obstructive sleep apnea and other pulmonary diseases is still under debate but has opened up a window to the role NO may play in the management of these diseases. The use of FeNO is reliable, cost effective and recommendable in both adults and children, and should be implemented in the management of patients with asthma and other respiratory conditions.

[Diagnosis and treatment of asthma: a guideline for respiratory specialists 2023 - published by the German Respiratory Society (DGP) e. V.]

The management of asthma has fundamentally changed during the past decades. The present guideline for the diagnosis and treatment of asthma was developed for respiratory specialists who need detailed and evidence-based information on the new diagnostic and therapeutic options in asthma. The guideline shows the new role of biomarkers, especially blood eosinophils and fractional exhaled NO (FeNO), in diagnostic algorithms of asthma. Of note, this guideline is the first worldwide to announce symptom prevention and asthma remission as the ultimate goals of asthma treatment, which can be achieved by using individually tailored, disease-modifying anti-asthmatic drugs such as inhaled steroids, allergen immunotherapy or biologics. In addition, the central role of the treatment of comorbidities is emphasized. Finally, the document addresses several challenges in asthma management, including asthma treatment during pregnancy, treatment of severe asthma or the diagnosis and treatment of work-related asthma.

Cough and cough hypersensitivity as treatable traits of asthma

Cough is a common and troublesome symptom in people with asthma and is often associated with poorer asthma control and exacerbations. Apart from asthma, other causes or comorbidities might underlie cough in asthma, such as rhinosinusitis and bronchiectasis. Eosinophilic inflammation and bronchoconstriction can lead to an acute episode of cough or worsen chronic cough. Cough hypersensitivity with laryngeal paraesthesia, allotussia, and hypertussia might underlie the cough of asthma through augmented sensory nerve excitability of upper-airway vagal sensory nerves. Cough associated with bronchoconstriction and type 2 inflammation should respond to inhaled corticosteroids and long-acting β-adrenoceptor agonist therapy. For cough hypersensitivity in adults, speech and language therapy and neuromodulators (eg, gabapentin) could be considered. In children, there is no consistent association of asthma with cough sensitivity or between cough and asthma severity. Further research is needed to realise the potential of cough as a measure of asthma control, to understand the mechanisms of cough in asthma, and to develop safe, effective treatments and a precision-medicine approach to the management of cough in asthma in children and adults.

Antitussive Use in Patients with Inadequately Controlled Moderate-to-Severe Asthma: A Post Hoc Analysis of the Omalizumab EXTRA Trial

Acute and chronic cough are common symptoms in patients with severe allergic asthma. Although asthma-related cough can be controlled by asthma-specific medications, both prescription and over-the-counter antitussives are often also necessary. The anti-immunoglobulin E monoclonal antibody omalizumab is an effective treatment for patients with moderate-to-severe asthma, but little is known about subsequent antitussive use patterns. This post hoc analysis examined data from the Phase 3 EXTRA study that included patients aged 12-75 years with inadequately controlled moderate-to-severe asthma. Baseline antitussive use was low overall (16/427, 3.7% for omalizumab and 18/421, 4.3% for placebo). Among patients with no baseline antitussive use (n = 411 omalizumab, n = 403 placebo), most patients (88.3% omalizumab, 83.4% placebo) reported not using antitussives during the 48-week treatment period. The percentage of patients using 1 antitussive was lower for patients treated with omalizumab than placebo (7.1% vs 13.2%), although the adjusted rate of antitussive use during the treatment period was similar for omalizumab and placebo (0.22 and 0.25). Non-narcotics were used more often than narcotics. In conclusion, this analysis found low use of antitussives in patients with severe asthma and suggests that omalizumab may have the potential to decrease antitussive use.

Multiple Chemical Sensitivity: It's time to catch up to the science

Multiple chemical sensitivity (MCS) is a complex medical condition associated with low dose chemical exposures. MCS is characterized by diverse features and common comorbidities, including fibromyalgia, cough hypersensitivity, asthma, and migraine, and stress/anxiety, with which the syndrome shares numerous neurobiological processes and altered functioning within diverse brain regions. Predictive factors linked to MCS comprise genetic influences, gene-environment interactions, oxidative stress, systemic inflammation, cell dysfunction, and psychosocial influences. The development of MCS may be attributed to the sensitization of transient receptor potential (TRP) receptors, notably TRPV1 and TRPA1. Capsaicin inhalation challenge studies demonstrated that TRPV1 sensitization is manifested in MCS, and functional brain imaging studies revealed that TRPV1 and TRPA1 agonists promote brain-region specific neuronal variations. Unfortunately, MCS has often been inappropriately viewed as stemming exclusively from psychological disturbances, which has fostered patients being stigmatized and ostracized, and often being denied accommodation for their disability. Evidence-based education is essential to provide appropriate support and advocacy. Greater recognition of receptor-mediated biological mechanisms should be incorporated in laws, and regulation of environmental exposures.

Usefulness of simultaneous impulse oscillometry and spirometry with airway response to bronchodilator in the diagnosis of asthmatic cough

Objective: Some of the most common causes of chronic cough include cough variant asthma (CVA), bronchial asthma (BA), and asthma-COPD overlap (ACO). Although there is some overlap in the etiology of these diseases, it is clinically important to attempt an early differential diagnosis due to treatment strategies and prognoses.Methods: Spirometry and impulse oscillometry (IOS) before and after bronchodilator inhalation were analyzed for clinically diagnosed CVA (cCVA, n = 203), BA (cBA, n = 222), and ACO (cACO, n = 61).Results: A significant difference in ΔFEV₁ was observed between cBA and cCVA (ΔFEV₁ improvement of 122.5 mL/5.4% and 65.7 mL/2.2%, respectively), but no difference was observed in ΔPEF, ΔV50, or ΔV25. Except for R20 (resistance at 20 Hz), significant differences between the three groups were observed in IOS. In IOS, cCVA and cBA showed comparable peripheral airway response to bronchodilator which was thought to be commensurate with changes in V50 and V25. cACO improved ΔFEV₁ improvement of 81.0 mL/6.2% and was distinguished by a downward respiratory system reactance (Xrs) waveform with a limited bronchodilator response. FEV₁/FVC, %FEV₁, and %V25 had relatively strong correlations with the three IOS parameters, X5 (reactance at 5 Hz), resonant frequency (Fres), and low-frequency reactance area (ALX), in the correlation between IOS and spirometers.Conclusion: Changes in IOS parameters were more sensitive in this study than changes in FEV₁ or the flow-volume curve. Considering the benefits and relevance of the two different tests, simultaneous IOS and spirometry testing were useful in the diagnosis of asthmatic cough.

Can clinical characteristics differentiate patients with unexplained chronic cough from patients with asthma and COPD?

Background: Chronic cough is reported in up to 20% of the adult population and often persists despite medical treatment with currently available therapies. Many clinical conditions, including asthma and chronic obstructive pulmonary disease (COPD), must be excluded before making a Unexplained chronic cough diagnosis. Methods: The primary objective was to use a large hospital dataset to compare clinical features of patients with a primary diagnosis of UCC with those with asthma or COPD without a primary diagnosis of UCC to help clinicians differentiate between these conditions more readily. Data were collected for all hospitalization and outpatient medical encounters for each patient between November 2013 and December 2018. Information included demographics, encounter dates, medications prescribed at every encounter for chronic cough, lung function testing, and hematologic parameters. Asthma and COPD were combined into one group to ensure there was no overlap with UCC and due to limitations of International Classification of Diseases coding to confirm an asthma(A)/COPD diagnosis. Results: Female gender represented 70% of encounters for UCC versus 61.8% for asthma/COPD (p < 0.0001); the mean age was 56.9 years for UCC versus 50.1 years for A/COPD (p < 0.0001). The number of patients on cough medications and the cough medication frequency were significantly higher in the UCC versus A/COPD group (p < 0.0001). UCC versus A/COPD patients had a total of eight versus three cough-related encounters over the study duration (i.e., 5 years) (<0.0001). The average interval between successive encounters was less for UCC (114 days) versus the A/COPD (288 days) group. Gender-adjusted Forced expiratory volume in the first second of exhalation/Forced vital capacity (FEV₁/FVC) ratios, residual volume%, and Diffusion capacity for carbon monoxide (DLCO%) were significantly higher in UCC versus A/COPD, whereas the response to bronchodilators of FEV₁, FVC and residual volumes were significantly greater in A/COPD patients. Conclusions: Clinical characteristics differentiating UCC from A/COPD could accelerate recognition of UCC diagnosis especially in the subspecialty setting where patients with these disorders are referred.

Airway inflammation and hyperresponsiveness in subjects with respiratory symptoms and normal spirometry

BACKGROUND

Subjects without a previous history of asthma, presenting with unexplained respiratory symptoms and normal spirometry, may exhibit airway hyperresponsiveness (AHR) in association with underlying eosinophilic (type 2 (T2)) inflammation, consistent with undiagnosed asthma. However, the prevalence of undiagnosed asthma in these subjects is unknown.

METHODS

In this observational study, inhaled corticosteroid-naïve adults without previously diagnosed lung disease reporting current respiratory symptoms and showing normal pre- and post-bronchodilator spirometry underwent fractional exhaled nitric oxide (F _ENO) measurement, methacholine challenge testing and induced sputum analysis. AHR was defined as a provocative concentration of methacholine causing a 20% fall in forced expiratory volume in 1 s (PC₂₀) <16 mg·mL^-1 and T2 inflammation was defined as sputum eosinophils >2% and/or F _ENO >25 ppb.

RESULTS

Out of 132 subjects (mean±sd age 57.6±14.2 years, 52% female), 47 (36% (95% CI 28-44%)) showed AHR: 20/132 (15% (95% CI 9-21%)) with PC₂₀ <4 mg·mL^-1 and 27/132 (21% (95% CI 14-28%)) with PC₂₀ 4-15.9 mg·mL^-1. Of 130 participants for whom sputum eosinophils, F _ENO or both results were obtained, 45 (35% (95% CI 27-43%)) had T2 inflammation. 14 participants (11% (95% CI 6-16%)) had sputum eosinophils >2% and PC₂₀ ≥16 mg·mL^-1, suggesting eosinophilic bronchitis. The prevalence of T2 inflammation was significantly higher in subjects with PC₂₀ <4 mg·mL^-1 (12/20 (60%)) than in those with PC₂₀ 4-15.9 mg·mL^-1 (8/27 (30%)) or ≥16 mg·mL^-1 (25/85 (29%)) (p=0.01).

CONCLUSIONS

Asthma, underlying T2 airway inflammation and eosinophilic bronchitis may remain undiagnosed in a high proportion of symptomatic subjects in the community who have normal pre- and post-bronchodilator spirometry.

Yardstick for managing cough, part 1: In adults and adolescent patients older than 14 years of age

Nationwide statistics in the United States and Australia reveal that cough of undifferentiated duration is the most common complaint for which patients of all ages seek medical care in the ambulatory setting. Management of chronic cough is one of the most common reasons for new patient visits to pulmonologists. Because symptomatic cough is such a common problem and so much has been learned about how to diagnose and treat cough of all durations but especially chronic cough, this 2-part yardstick has been written to review in a practical way the latest evidence-based guidelines most of which have been developed from recent high quality systematic reviews on how best to manage cough of all durations in adults, adolescents, and children. In this manuscript, part 1 of the 2-part series, we provide evidence-based, and expert opinion recommendations on the management of chronic cough in adult and adolescent patients (>14 years of age).

Narrative Review of the Mechanisms and Treatment of Cough in Asthma, Cough Variant Asthma, and Non-asthmatic Eosinophilic Bronchitis

Chronic cough is a debilitating condition affecting 10-12% of the general population and is one of the leading causes for referral to secondary care. Many conditions have been associated with chronic cough, including asthma, gastro-esophageal reflux disease and upper airways cough syndrome. Inflammatory airway conditions including cough variant asthma (CVA) and non-asthmatic eosinophilic bronchitis (NAEB) contribute to a significant proportion of presentations with chronic cough, with differing diagnostic criteria and different responses to commonly used asthma therapy for their respective diagnoses. Mechanistic studies in both animal models and humans have identified increased neuronal sensitivity and subsequent central sensitization. These mechanisms include inflammatory-mediated nociceptor sensitization and alterations of afferent nerve terminal excitability, phenotypic changes in the vagal afferent neurons over time, and central neuroplasticity resulting from increased synaptic signalling from peripheral afferents. The aim of this review is to discuss the mechanisms, neurophysiology, and management approaches currently available for patients presenting with chronic cough with underlying asthma, CVA, and NAEB and to shed a light on areas of further research required to elucidate the mechanisms of cough in this patient population.

Effects of treatment with montelukast alone, budesonide/formoterol alone and a combination of both in cough variant asthma

Background

Whether cysteinyl-leukotriene receptor antagonists (LTRAs) have a similar antitussive effect to inhaled corticosteroids and long-acting β2-agonist (ICS/LABA), and that LTRA plus ICS/LABA is superior to LTRAs alone or ICS/LABA alone in treating cough variant asthma (CVA) remain unclear. This study aimed to investigate and compare the efficacy of montelukast alone, budesonide/formoterol alone and the combination of both in the treatment of CVA.

Methods

Ninety-nine CVA patients were assigned randomly in a 1:1:1 ratio to receive montelukast (M group: 10 mg, once daily), budesonide/formoterol (BF group: 160/4.5 μg, one puff, twice daily), or montelukast plus budesonide/formoterol (MBF group) for 8 weeks. The primary outcomes were changes in the cough visual analogue scale (VAS) score, daytime cough symptom score (CSS) and night-time CSS, and the secondary outcomes comprised changes in cough reflex sensitivity (CRS), the percentage of sputum eosinophils (sputum Eos%) and fractional exhaled nitric oxide (FeNO). CRS was presented with the lowest concentration of capsaicin that induced at least 5 coughs (C5). The repeated measure was used in data analysis.

Results

The median cough VAS score (median from 6.0 to 2.0 in the M group, 5.0 to 1.0 in the BF group and 6.0 to 1.0 in the MBF group, all p < 0.001), daytime CSS (all p < 0.01) and night-time CSS (all p < 0.001) decreased significantly in all three groups after treatment for 8 weeks. Meanwhile, the LogC5 and sputum Eos% improved significantly in all three groups after 8 weeks treatment (all p < 0.05). No significant differences were found in the changes of the VAS score, daytime and night-time CSSs, LogC5 and sputum Eos% among the three groups from baseline to week 8 (all p > 0.05). The BF and MBF groups also showed significant decreases in FeNO after 8 weeks treatment (p = 0.001 and p = 0.008, respectively), while no significant change was found in the M group (p = 0.457). Treatment with MBF for 8 weeks significantly improved the FEV₁/FVC as well as the MMEF% pred and decreased the blood Eos% (all p < 0.05).

Conclusions

Montelukast alone, budesonide/formoterol alone and a combination of both were effective in improving cough symptom, decreasing cough reflex sensitivity and alleviating eosinophilic airway inflammation in patients with CVA, and the antitussive effect and anti-eosinophilic airway inflammation were similar.

Trial registration ClinicalTrials.gov, number NCT01404013.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02114-6.

Cough hypersensitivity and chronic cough

Chronic cough is globally prevalent across all age groups. This disorder is challenging to treat because many pulmonary and extrapulmonary conditions can present with chronic cough, and cough can also be present without any identifiable underlying cause or be refractory to therapies that improve associated conditions. Most patients with chronic cough have cough hypersensitivity, which is characterized by increased neural responsivity to a range of stimuli that affect the airways and lungs, and other tissues innervated by common nerve supplies. Cough hypersensitivity presents as excessive coughing often in response to relatively innocuous stimuli, causing significant psychophysical morbidity and affecting patients' quality of life. Understanding of the mechanisms that contribute to cough hypersensitivity and excessive coughing in different patient populations and across the lifespan is advancing and has contributed to the development of new therapies for chronic cough in adults. Owing to differences in the pathology, the organs involved and individual patient factors, treatment of chronic cough is progressing towards a personalized approach, and, in the future, novel ways to endotype patients with cough may prove valuable in management.

WAO-ARIA consensus on chronic cough - Part III: Management strategies in primary and cough-specialty care. Updates in COVID-19

Background

Chronic cough management necessitates a clear integrated care pathway approach. Primary care physicians initially encounter the majority of chronic cough patients, yet their role in proper management can prove challenging due to limited access to advanced diagnostic testing. A multidisciplinary approach involving otolaryngologists and chest physicians, allergists, and gastroenterologists, among others, is central to the optimal diagnosis and treatment of conditions which underly or worsen cough. These include infectious and inflammatory, upper and lower airway pathologies, or gastro-esophageal reflux. Despite the wide armamentarium of ancillary testing conducted in cough multidisciplinary care, such management can improve cough but seldom resolves it completely. This can be due partly to the limited data on the role of tests (eg, spirometry, exhaled nitric oxide), as well as classical pharmacotherapy conducted in multidisciplinary specialties for chronic cough. Other important factors include presence of multiple concomitant cough trigger mechanisms and the central neuronal complexity of chronic cough. Subsequent management conducted by cough specialists aims at control of cough refractory to prior interventions and includes cough-specific behavioral counseling and pharmacotherapy with neuromodulators, among others. Preliminary data on the role of neuromodulators in a proof-of-concept manner are encouraging but lack strong evidence on efficacy and safety.

Objectives

The World Allergy Organization (WAO)/Allergic Rhinitis and its Impact on Asthma (ARIA) Joint Committee on Chronic Cough reviewed the recent literature on management of chronic cough in primary, multidisciplinary, and cough-specialty care. Knowledge gaps in diagnostic testing, classical and neuromodulator pharmacotherapy, in addition to behavioral therapy of chronic cough were also analyzed.

Outcomes

This third part of the WAO/ARIA consensus on chronic cough suggests a management algorithm of chronic cough in an integrated care pathway approach. Insights into the inherent limitations of multidisciplinary cough diagnostic testing, efficacy and safety of currently available antitussive pharmacotherapy, or the recently recognized behavioral therapy, can significantly improve the standards of care in patients with chronic cough.

Chronic cough in asthma is associated with increased airway inflammation, more comorbidities, and worse clinical outcomes

Background: Cough is often the most prominent and intractable symptom reported by patients with asthma, but few studies have explored the characteristics of patients with asthma and with chronic cough (CC) in a real-world setting. Methods: In a prospective cohort study, patients ages ≥ 18 years with stable asthma were consecutively recruited at the West China Hospital, Sichuan University. The patients were classified as having asthma with CC (the CC group) or asthma with non-CC (the non-CC group) after 3 months of optimized asthma therapy according to standard guidelines. Multidimensional assessment was performed at baseline, followed by a 12-month follow-up to assess asthma exacerbations. Results: Of 323 patients with asthma, 127 patients were assigned to the CC group and 196 patients were assigned to the non-CC group. The participants with CC were older and had more airflow obstruction; worse asthma control and quality of life; increased airway inflammation; upper respiratory tract infection as a trigger; and more comorbidities, such as psychological dysfunction, rhinitis, chronic obstructive pulmonary disease, and bronchiectasis. They reported greater work productivity loss and daily activity impairment, and increased moderate-to-severe exacerbations. Conclusion: The participants with asthma and with CC had a significant disease burden, with increased exacerbations, health-care utilization, and impaired work productivity and daily activity. These observations indicated potential clinical implications in patients with asthma and with CC, and call for more attention to this aspect of asthma.

Clinical and Inflammatory Characteristics of the Chinese APAC Cough Variant Asthma Cohort

Background

The AtyPical Asthma in China (APAC) cohort is a multi-center prospective, observational cohort set-up to investigate the clinical, pathophysiological features, prognosis, and mechanisms of cough variant asthma (CVA).

Objectives

To present the characteristics of newly physician-diagnosed adults with CVA (n = 328) compared to mild-moderate classic asthma (CA, n = 206).

Methods and Main Results

CVA subjects showed a higher proportion of female (67.1 vs. 55.3%, P = 0.0084), abnormal laryngopharyngeal sensations (71 vs. 51%, p < 0.0001) than CA, but presented with near normal spirometry and higher methacholine PD20-FEV1 values [4.2 (1, 8.6) vs. 0.8 (0.4, 4.7), P < 0.0001]. Lower fractional exhaled nitric oxide (FENO) levels [38.5 (19.8, 72.5) vs. 53. (28.5, 92.2), P = 0.0019], blood eosinophil counts [0.2 (0.1, 0.4) vs. 0.3 (0.2, 0.5), P = 0.0014], and sputum eosinophils [2.3 (0.3, 8.0) vs. 12.2 (2, 34.5), p < 0.0001] were found in CVA. Despite lower total serum IgE levels in CVA, there was similar proportion of atopy in both groups. The prevalence of cough in CA was 86.4%, while CVA reported more severe cough on Visual Analog Scale, Cough Evaluation Test, and Leicester Cough Questionnaire, similar anxiety and depression scores but better asthma control scores as reflected by Asthma Control Test compared to CA. No correlation was found between cough assessment outcomes and sputum eosinophil count, blood eosinophil count, FENO, spirometry variables, or PD20-FEV1.

Conclusion

Cough variant asthma is distinctive from classic asthma in regard to clinical features, lung function, and airway inflammation. Quality of life is badly impaired as well in spite of better asthma control scores.

Blood eosinophils as a predictor of treatment response in adults with difficult-to-treat chronic cough

There is lack of evidence on the role of blood eosinophil count (BEC) as a predictor of treatment response in patients with chronic cough. The study aimed to evaluate BEC as a predictor of treatment response in all non-smoking adults with chronic cough and normal chest radiograph referred to cough clinic and in a subgroup of patients with chronic cough due to asthma or non-asthmatic eosinophilic bronchitis (NAEB).

This prospective cohort study included 142 consecutive, non-smoking patients referred to our cough centre due to chronic cough. The management of chronic cough was performed according to the current recommendations. At least a 30-mm decrease of 100-mm visual analogue scale in cough severity and a 1.3 points improvement in Leicester Cough Questionnaire were classified as a good therapeutic response.

There was a predominance of females (72.5%), median age 57.5 years with long-lasting, severe cough (median cough duration 60 months, severity 55/100 mm). Asthma and NAEB were diagnosed in 47.2% and 4.9% of patients, respectively. After 12–16 weeks of therapy, a good response to chronic cough treatment was found in 31.0% of all patients. A weak positive correlation was demonstrated between reduction in cough severity and BEC (r=0.28, p<0.001). Area under the curve for all patients with chronic cough was 0.62 with the optimal BEC cut-off for prediction of treatment response set at 237 cells·µL⁻¹ and for patients with chronic cough due to asthma/NAEB was 0.68 (95% CI 0.55–0.81) with the cut-off at 150 cells·µL⁻¹.

BEC is a poor predictor of treatment response in adults with chronic cough treated in the cough centre.

Evaluation of blood eosinophil count has limited value in prediction of therapeutic response in patients with difficult-to-treat chronic coughhttps://bit.ly/3EjaYsZ

Revised Korean Cough Guidelines, 2020: Recommendations and Summary Statements

Cough is the most common respiratory symptom that can have various causes. It is a major clinical problem that can reduce a patient's quality of life. Thus, clinical guidelines for the treatment of cough were established in 2014 by the cough guideline committee under the Korean Academy of Tuberculosis and Respiratory Diseases. From October 2018 to July 2020, cough guidelines were revised by members of the committee based on the first guidelines. The purpose of these guidelines is to help clinicians efficiently diagnose and treat patients with cough. This article highlights the recommendations and summary of the revised Korean cough guidelines. It includes a revised algorithm for the evaluation of acute, subacute, and chronic cough. For a chronic cough, upper airway cough syndrome (UACS), cough variant asthma (CVA), and gastroesophageal reflux disease (GERD) should be considered in differential diagnoses. If UACS is suspected, first-generation antihistamines and nasal decongestants can be used empirically. In cases with CVA, inhaled corticosteroids are recommended to improve cough. In patients with suspected chronic cough due to symptomatic GERD, proton pump inhibitors are recommended. Chronic bronchitis, bronchiectasis, bronchiolitis, lung cancer, aspiration, intake of angiotensin-converting enzyme inhibitor, intake of dipeptidyl peptidase-4 inhibitor, habitual cough, psychogenic cough, interstitial lung disease, environmental and occupational factors, tuberculosis, obstructive sleep apnea, peritoneal dialysis, and unexplained cough can also be considered as causes of a chronic cough. Chronic cough due to laryngeal dysfunction syndrome has been newly added to the guidelines.

Does bronchial hyperresponsiveness predict a diagnosis of cough variant asthma in adults with chronic cough: a cohort study

Bronchial hyperresponsiveness is a typical, but non-specific feature of cough variant asthma (CVA). This study aimed to determine whether bronchial hyperresponsiveness may be considered as a predictor of CVA in non-smoking adults with chronic cough (CC). The study included 55 patients with CC and bronchial hyperresponsiveness confirmed in the methacholine provocation test, in whom an anti-asthmatic, gradually intensified treatment was introduced. The diagnosis of CVA was established if the improvement in cough severity and cough-related quality of life in LCQ were noted.The study showed a high positive predictive value of bronchial hyperresponsiveness in this population. Cough severity and cough related quality of life were not related to the severity of bronchial hyperresponsiveness in CVA patients. A poor treatment outcome was related to a low baseline capsaicin threshold and the occurrence of gastroesophageal reflux-related symptoms. In conclusion, bronchial hyperresponsiveness could be considered as a predictor of cough variant asthma in non-smoking adults with CC.

Limosilactobacillus reuteri DSM-17938 for preventing cough in adults with mild allergic asthma: A double-blind randomized placebo-controlled cross-over study

BACKGROUND

Cough is a common troublesome symptom in asthma which is neuronally mediated. Limosilactobacillus reuteri DSM-17938 (L. reuteri DSM-17938) is a probiotic shown to be effective in pre-clinical models at suppressing neuronal responses to capsaicin, a transient receptor potential vanilloid agonist (TRPV1).

OBJECTIVE

Investigate the effects of DSM-17938 versus matched placebo on capsaicin-evoked coughs in mild allergic asthmatics.

METHODS

We performed a 4-visit, randomized, double-blind, placebo-controlled, two-way cross-over study comparing full dose cough responses with inhaled capsaicin in mild allergic asthmatics after 1 month of treatment with DSM-17938 compared with matched placebo. Randomization and allocation to trial group were carried out by a central computer system. Histamine skin prick testing, airway hyper-responsiveness and inflammatory cells in induced sputum were measured at every visit. Blood was collected to extract PBMCs and stimulated with CD3/CD28 to ascertain the effects of DSM-17938 /placebo on T-cell cytokine responses.

RESULTS

Seventeen subjects were recruited and 15 completed the study (8 females, mean age 27.3 years). There was no difference in the change in maximum capsaicin-evoked coughs (Emax) after treatment with L. reuteri DSM-17938 compared with placebo [mean difference 2.07 coughs (95% CI -2.77 to 6.91, p = .38) or relative changes in geometric mean ratios for the dose evoking at least half the Emax (ED50) [1.05 (95% CI 0.31-3.58, p = .94)], concentration evoking 2 coughs (C2) [0.63 (0.26-1.53), p = .28] and 5 coughs (C5) [0.79 (0.25-2.50), p = .67]. There was no effect on histamine skin prick wheal size, intensity of itch sensation, methacholine PC20, airway inflammation or T-cell responses after stimulation with CD3/CD28. There were no serious adverse events. One subject developed a mild upper respiratory tract infection and another mild transient nausea whilst on DSM-17938.

CONCLUSION

In this small study in adults with mild allergic asthma, we found no evidence that L. reuteri DSM-17938 has any systemic effects on airway nerves, smooth muscle, sputum inflammatory cells, skin responses or T-cell responses after oral consumption.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier: NCT03603522.

Narrative Review: how long should patients with cough variant asthma or non-asthmatic eosinophilic bronchitis be treated?

The causes of chronic cough can be categorized into eosinophilic and noneosinophilic disorders, and approximately 30% to 50% of people with chronic cough have eosinophilic airway inflammation, the presence of which can be confirmed by sputum eosinophilia or elevated exhaled nitric-oxide levels. Cough variant asthma (CVA) is a phenotype of asthma which lacks wheezing or dyspnea, and consistently one of the most common causes of chronic cough worldwide. CVA and non-asthmatic eosinophilic bronchitis (NAEB) shares common feature such as chronic dry cough, eosinophilic inflammation, and development of chronic airflow obstruction (CAO) and asthma in a subset of patients. The distinctive characteristic of these conditions is the presence of airway hyperresponsiveness in CVA but not in NAEB. Coughing is responsive to bronchodilators such as beta-agonists in CVA, but such feature has not been clarified in NAEB. Inhaled corticosteroids (ICSs) are the first-line treatment, and leukotriene receptor antagonists are also effective, in patients with both CVA and NAEB. This review will give an outline of clinical and physiological features, and prognosis and its determinants of CVA and EBNA. Further, the rationale and evidence, despite limited, for the need of long-term treatment will be discussed. The development of airway remodeling due to mechanical stress to the airways exerted by long-standing coughing will also be discussed.