Inflammatory Subtypes in Classic Asthma and Cough Variant Asthma

Airway inflammation, bronchial hyperresponsiveness, and anti-asthma therapy responses in cough variant asthma and classic asthma with FEV1% ≥80% predicted

OBJECTIVE

To explore the differentiation of airway inflammation, bronchial hyperresponsiveness and anti-asthma therapy responses between the cough variant asthma (CVA) and classic asthma (CA) patients with FEV1% ≥80% predicted.

METHODS

In the first monocentre retrospective cross-sectional study, 402 patients with suspicion of CA and 544 patients with chronic cough were enrolled. Further prospective monocentre study was conducted and 66 patients of suspected asthma with negative bronchial dilation test (BDT) but positive bronchial challenge (BCT) test were enrolled and followed up for 4 weeks.

RESULTS

CA patients had higher fractional exhaled nitric oxide (FENO) values than CVA patients (36.0 ppb vs. 24.0 ppb, p < 0.0001). The predictive value of FENO for positive BCT was significantly lower in chronic cough patients compared to those with suspicion of CA (AUC = 0.603 vs. 0.728). Following four weeks anti-asthma therapy, both the CVA and CA groups showed significant improvement in both the large and small airway function and symptom relief. There was no significant difference between the respective groups. The two most valuable spirometric variables for predicting a positive response to anti-asthma treatment were the improvements of FEV1 (ΔFEV1, cut-off values = 90 ml for CA and 110 ml for CVA) and FEV1% (ΔFEV1%, cut-off values = 3.49% for CA and 2.59% for CVA) after BDT in baseline of CA and CVA patients, respectively.

CONCLUSION

Patients with CVA exhibited lower levels of airway eosinophilic inflammation compared to those with mild CA. Most patients with mild CA and CVA could benefit promptly from anti-asthma treatment. Additionally, an improvement in FEV1 and FEV1% during BDT can potentially predict positive responses to anti-asthma therapy in both groups.

Cough-Variant Asthma: A Review of Clinical Characteristics, Diagnosis, and Pathophysiology

Chronic cough is among the most common symptoms prompting medical care. Cough-variant asthma (CVA) is an asthma subset where cough is the primary symptom, without wheezing, chest tightness, or dyspnea. It is an important cause of chronic cough, estimated to account for 25% to 42% of cases, but likely underdiagnosed due to delayed recognition and pitfalls of diagnostic testing. Early recognition and treatment can reduce morbidity and delay its progression to more typical asthma. This review details the clinical characteristics, diagnosis, pathophysiology, and treatment of CVA and contrasts it with classic asthma and other causes of chronic cough.

Retrospective, observational study of different medication regimens and outcome in children with cough variant asthma

OBJECTIVE

This retrospective longitudinal cohort study aimed to explore the best therapeutic regimen and treatment duration of cough variant asthma (CVA) in children.

METHODS

A total of 314 children with CVA were divided into receive inhaled corticosteroids (ICS) combined with long-acting beta2-agonist (LABA) group, ICS combined with leukotriene receptor antagonists (LTRA) group, ICS monotherapy group and LTRA monotherapy group. All clinical data were statistically analyzed. Logistic regression model was used to compare the advantages and disadvantages of different treatment schemes at each follow-up time point and the best treatment scheme. The Cox proportional hazard regression model based on inverse probability weighting was used to compare the effects of different medication regimens on adverse outcomes with asthma recurrence or progression as the end point.

RESULTS

(1) After comprehensive analysis, ICS + LABA group was the preferred control regimen for CVA within 8 weeks. After 8 weeks of diagnosis, the efficacy of ICS group or LTRA group was comparable to that of ICS + LABA group and ICS + LTRA group. (2) The ICS + LABA group showed a significant improvement in cough at an early stage, particularly at 4 weeks; the symptoms of ICS + LTRA and ICS groups were significantly improved at 36 weeks. The LTRA group alone showed significant improvement at 20 weeks.

CONCLUSION

ICS + LABA, ICS + LTRA, ICS alone and LTRA alone can effectively treat CVA. ICS + LABA could improve the symptoms most quickly within 8 weeks after CVA diagnosis, followed by ICS + LATR group. After 8 weeks, it can be reduced to ICS alone to control CVA for at least 36 weeks based on the remission of symptoms in children.

Impact of pollen season and viral disease COVID-19 on respiratory function of the adult population in Eastern Slovakia: analysis of spirometric data and results of a questionnaire survey

INTRODUCTION

Asthma is a chronic heterogeneous disease with characteristic symptoms, but with proper treatment the patient can lead a full life. In patients with allergic asthma, symptoms appear after irritation with an allergen, most often in the pollen season. In 2019, the viral disease COVID-19 appeared, which, especially in people with asthma, led not only to an asthma attack, but also to other serious diseases.

METHODS

The main aim was to investigate differences in patients' health status by comparing spirometric values in and out of pollen season (A), spirometric values before and after COVID-19 viral illness (B) and an anonymous questionnaire (C). Spirometric values were recorded in each patient (control group - patients diagnosed with asthma, research group - patients after overcoming COVID-19 disease) in 3 cycles, namely (in the pollen period, in the non-pollen period and after overcoming COVID-19 disease - at an interval of 2 months after a negative PCR test).

RESULTS

We observed significant results during the individual spirometry performed (A) during the pollen season and non-pollen season. We observed the same in patients after they received COVID-19 treatment (B). Patients were also asked questions regarding family history, symptoms and their variability, worsening of the condition or correct inhalation technique (C).

CONCLUSION

Our research shows that the PEF parameter is most affected by the pollen and non-pollen season in asthmatic patients. Significant differences in PEF parameter were observed between genders, where we observed highly significant statistical significance of PEF parameter in pollen and non-pollen season in females.

Microbiota Alterations in Lung, Ileum, and Colon of Guinea Pigs with Cough Variant Asthma

Alterations in the microbiota composition, or ecological dysbiosis, have been implicated in the development of various diseases, including allergic diseases and asthma. Examining the relationship between microbiota alterations in the host and cough variant asthma (CVA) may facilitate the discovery of novel therapeutic strategies. To elucidate the diversity and difference of microbiota across three ecological niches, we performed 16S rDNA amplicon sequencing on lung, ileum, and colon samples. We assessed the levels of interleukin-12 (IL-12) and interleukin-13 (IL-13) in guinea pig bronchoalveolar lavage fluid using the enzyme-linked immunosorbent assay (ELISA). We applied Spearman's analytical method to evaluate the correlation between microbiota and cytokines. The results demonstrated that the relative abundance, α-diversity, and β-diversity of the microbial composition of the lung, ileum, and colon varied considerably. The ELISA results indicated a substantial increase in the level of IL-13 and a decreasing trend in the level of IL-12 in the CVA guinea pigs. The Spearman analysis identified a correlation between Mycoplasma, Faecalibaculum, and Ruminococcus and the inflammatory factors in the CVA guinea pigs. Our guinea pig model showed that core microorganisms, such as Mycoplasma in the lung, Faecalibaculum in the ileum, and Ruminococcus in the colon, may play a crucial role in the pathogenesis of CVA. The most conspicuous changes in the ecological niche were observed in the guinea pig ileum, followed by the lung, while relatively minor changes were observed in the colon. Notably, the microbial structure of the ileum niche approximated that of the colon niche. Therefore, the results of this study suggest that CVA development is closely related to the dysregulation of ileal, lung, and colon microbiota and the ensuing inflammatory changes in the lung.

Evaluation and management of chronic cough in adults

Background: Chronic cough (CC), a cough that lasts > 8 weeks, has an overall prevalence of 5-11% in adults, peaking between 60 and 80 years of age. Of the 15% of patients who remain undiagnosed or refractory to treatment, two thirds are women. Objective: The objective was to present an updated evidence-based algorithmic approach for evaluating and managing CC, with emphasis on treatment modalities for refractory CC. Methods: A literature search was conducted of medical literature data bases for guidelines, position papers, systematic reviews, and clinical trials from January 2022 to June 2023, on the evaluation and management of CC. Results: The initial assessment should be limited to a detailed history, physical examination, chest radiograph, spirometry, exhaled nitric oxide, blood eosinophil count, and measurement of cough severity and quality of life by using validated instruments. The top diagnoses to consider are asthma, chronic obstructive pulmonary disease, nonasthmatic eosinophilic bronchitis, gastroesophageal reflux disease, and upper airway cough syndrome. Additional studies are only obtained when red flags are present or the patient fails to respond after avoidance of high-risk factors, e.g., smoking and angiotensin-converting enzyme inhibitors, and 4-6 weeks of empiric treatment for the most likely respiratory and gastrointestinal diseases. When diagnostic tests and/or specific directed treatments fail to control CC, low-dose morphine (preferred), gabapentin, pregabalin, and/or cough control therapy are recommended. Non-narcotic purinergic 2×3 (P2×3) receptor antagonists, gafapixant and campilixant, are currently being studied for CC. Conclusion: For the evaluation and management of patients with CC, clinicians should use an algorithmic approach and identify "red flags," reduce high-risk factors, and use empiric treatment for the five top diagnoses before extensive diagnostic testing. Current treatment for refractory cough is limited to symptomatic management.

Exhaled Nitric Oxide as Biomarker of Type 2 Diseases

Nitric oxide (NO) is a short-lived gas molecule which has been studied for its role as a signaling molecule in the vasculature and later, in a broader view, as a cellular messenger in many other biological processes such as immunity and inflammation, cell survival, apoptosis, and aging. Fractional exhaled nitric oxide (FeNO) is a convenient, easy-to-obtain, and non-invasive method for assessing active, mainly Th2-driven, airway inflammation, which is sensitive to treatment with standard anti-inflammatory therapy. Consequently, FeNO serves as a valued tool to aid the diagnosis and monitoring of several asthma phenotypes. More recently, FeNO has been evaluated in several other respiratory and/or immunological conditions, including allergic rhinitis, chronic rhinosinusitis with/without nasal polyps, atopic dermatitis, eosinophilic esophagitis, and food allergy. In this review, we aim to provide an extensive overview of the current state of knowledge about FeNO as a biomarker in type 2 inflammation, outlining past and recent data on the application of its measurement in patients affected by a broad variety of atopic/allergic disorders.

Asthma Phenotypes in the Era of Personalized Medicine

Asthma is a widespread disease affecting approximately 300-million people globally. This condition leads to significant morbidity, mortality, and economic strain worldwide. Recent clinical and laboratory research advancements have illuminated the immunological factors contributing to asthma. As of now, asthma is understood to be a heterogeneous disease. Personalized medicine involves categorizing asthma by its endotypes, linking observable characteristics to specific immunological mechanisms. Identifying these endotypic mechanisms is paramount in accurately profiling patients and tailoring therapeutic approaches using innovative biological agents targeting distinct immune pathways. This article presents a synopsis of the key immunological mechanisms implicated in the pathogenesis and manifestation of the disease's phenotypic traits and individualized treatments for severe asthma subtypes.

Clinical significance of fractional exhaled nitric oxide and periostin as potential markers to assess therapeutic efficacy in patients with cough variant asthma

BACKGROUND

In Japan, cough variant asthma (CVA) is the most common etiology of chronic cough. Contrary to substantial progress in understanding the roles of various factors in classic asthma, little is known regarding the pathogenesis and development of CVA. Furthermore, few studies have explored valuable biomarkers for evaluating the therapeutic efficacy of patients with CVA.

METHODS

We conducted a single-center, prospective study to investigate the clinical significance of various clinical factors as potential "therapeutic" markers for CVA.

RESULTS

From December 2019 to September 2020, we enrolled 20 patients with CVA and 10 age-matched healthy control subjects. Fractional exhaled nitric oxide (FeNO) values were significantly higher in patients with CVA than those in healthy controls. All patients with CVA commenced treatment at the initial visit, which markedly alleviated symptoms 12 weeks after treatment. FeNO values and serum periostin levels were significantly decreased following treatment, and altered FeNO values correlated with improved visual analogue scale scores of symptoms. Moreover, changes in both FeNO values and serum periostin levels were significantly correlated with increased values of some pulmonary function tests while also correlating with each other.

CONCLUSIONS

Our observations indicate the usefulness of FeNO and periostin as potential "therapeutic" markers for CVA. To the best of our knowledge, this is the first report demonstrating the clinical significance of these factors as potential biomarkers to assess therapeutic efficacy in patients with CVA.

Study on the Relationship Between Bronchoalveolar Lavage Fluid Cell Count, Th1/Th2 Cytokines and Pulmonary Function in Patients with Cough Variant Asthma

OBJECTIVE

This study aimed to compare lung function and airway inflammation among cough variant asthma (CVA), chronic cough and classical asthma (CA) and investigate the relationship between these indicators and their possible mechanisms of action in the progression of CVA to CA.

METHODS

36 patients with chronic cough, 39 patients with CA, and 57 patients with CVA were included in this study. Pulmonary function tests, bronchial provocation tests and FeNO tests were performed. The patients' bronchoalveolar lavage fluid (BALF) was collected, the cells in BALF were counted, and the levels of Th1 and Th2 cytokines were detected.

RESULTS

The neutrophils, lymphocytes, and eosinophils in BALF in the CA and CVA groups were significantly higher than those in the chronic cough group. Also, they were negatively correlated with FEV1, FVC, and FEV1/FVC and positively correlated with IgE and FeNO. The expression of Th2-related cytokines was increased in CVA and CA patients, and it was positively correlated with FEV1, FVC and FEV1/FVC and negatively correlated with IgE and FeNO, while the results of Th1-related cytokines were the opposite of those for Th2-related cytokines.

CONCLUSION

CVA differs from asthma and chronic cough in terms of Th1/Th2 cytokines and lung function and provides a reference for understanding the disease mechanism of early clinical progression of CVA to CA.

The Effectiveness and Safety of Huangqi Xixin Decoction for Cough Variant Asthma: A Systematic Review and Meta-Analysis

Objective

A comprehensive and systematic review is needed to evaluate the safety and effectiveness of Huangqi Xixin decoction (HQXXD) for cough variant asthma (CVA). In this systematic review, we comprehensively interrogate the safety and effectiveness of HQXXD for CVA.

Methods

An overall search for studies in main English and Chinese electronic databases from their inception to June 30, 2022, was performed. Randomized controlled trials (RCTs) involving HQXXD for CVA were included. According to Cochrane Reviewer's Handbook, the risk of bias related to the included studies was evaluated. A meta-analysis using RevMan 5.4 software from the Cochrane Collaboration was used to integrate the outcomes of the included RCTs.

Results

A systematic review and meta-analysis were conducted using the seven eligible RCTs that had been retrieved. The included RCT-related risk of bias was evaluated. According to the findings of the meta-analysis, the HQXXD group had significantly higher total effective rates of clinical efficacy and airway responsiveness, and a significantly lower recurrence rate in comparison with the conventional Western medicine treatment group.

Conclusion

In the treatment of CVA patients, HQXXD is safe and effective, which benefits clinical efficacy and airway responsiveness, reduces the recurrence rate, and has no adverse effects.

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.

Allergic shiners in a patient with cough-variant asthma: a case report

BACKGROUND

Chronic cough, with a duration of coughing of more than 8 weeks in adults, affects 5-10% of the general population. One of the most common causes of chronic cough is cough-variant asthma, which accounts for approximately one-third of cases. This phenotype of asthma is characterized by extreme sensitivity of the neuronal pathways mediating cough to environmental irritants, which results in an urge to cough. This case is an example of cough-variant asthma presenting with allergic shiners due to her severe cough.

CASE PRESENTATION

A 38-year-old Iranian woman, who was well before the start of the coronavirus disease 2019 pandemic, presented with a nonproductive hacking cough that had begun after excessive use of antiseptic solutions. The only positive finding on physical examination was a reddish-purple rash on and around the eyelids mimicking a heliotrope rash, which had probably evolved due to the severity of the cough. The results of the pulmonary function test were within normal limits. Methacholine challenge test and chest x-ray were both normal. Chest high-resolution computed tomography revealed hyperinflation and tree-in-bud opacities. All other laboratory tests were normal. Because of the reversibility in her pulmonary function test, despite normal baseline parameters, asthma treatment was initiated, resulting in disappearance of the cough and the eye discoloration, being indicative of the correct diagnosis and proper treatment.

CONCLUSION

Patients with cough-variant asthma may often have no other classic symptoms of asthma other than cough.

Asthma in COVID-19: Mitigating or exacerbating? An interesting case report

Introduction

Bronchial asthma is an age-old disease whereas COVID-19 is an officially declared pandemic on March 11, 2020 by WHO. Since both are primarily a disease of the respiratory system, researchers across the globe tried to explore the potential relationship between them; to date, there is no convincing data. Here, we tried to present a case to explore potential relationships between these two, if present.

Case presentation

A 30-year-old male patient with well-controlled cough variant asthma was diagnosed with a case of covid-19 infection 12 months back. All other sign symptoms subsided except dry cough. The patient is treated with an inhaled bronchodilator, oral and inhaled steroid, Tab montelukast as well as other conservative management like hot water vapor, lozenge, honey, etc but symptoms were not controlled for the last 12 months. The patient could not do his job because of this problem. All examination and investigation findings were normal. After long-term use of inhaled steroids, he is now 50–60% improved and gradually improving.

Discussion

Covid can exacerbate cough in an asthmatic patient. Neuronal activation and neuroinflammatory mechanisms may aggravate this cough after covid. Diagnosis confirmed clinically with the relevant improvement of symptoms. Other important differentials were excluded by appropriate history, examinations, and investigation. Cough is improved by steroids in this case.

Conclusion

Summary of conclusion: Cough variant asthma may be aggravated with covid 19 infection and meticulous history, treatment, and follow up needed for an asthmatic patient who is infected with covid 19.

Inflammatory Phenotypes of Cough Variant Asthma as Response Predictors to Anti-Asthmatic Therapy

Background

Eosinophilic inflammatory phenotype was thought to be the most common phenotype of cough variant asthma (CVA), nevertheless other phenotypes were also reported.

Purpose

The study aimed to analyze the inflammatory phenotypes of CVA in relation to treatment response to the stepwise anti-asthmatic treatment.

Patients and Methods

The study included 45 patients with chronic cough (CC) and suspicion of CVA (normal chest X-ray, presence of bronchial hyperresponsiveness and no history of wheezing or dyspnea) in whom induced sputum was successfully collected. Based on the cellular composition of the sputum, patients were divided into major inflammatory phenotypes: eosinophilic, neutrophilic, paucigranulocytic or mixed granulocytic. A stepwise treatment, including inhaled corticosteroids with long-acting β₂-agonist, montelukast and short-term therapy with prednisone was initiated. Good treatment response was defined as the reduction in cough severity at least 20 mm from the baseline in visual analogue scale and improvement in cough-related quality of life assessed by the Leicester cough questionnaire at least 1.3 points after any of three steps.

Results

Finally, 40/45 (88.9%) patients improved after therapy. Eosinophilic asthma was found in 13/40 (32.5%) patients, neutrophilic in 6/40 (15.0%) and paucigranulocytic pattern in 21/40 (52.5%) patients. No one demonstrated a mixed granulocytic phenotype. The response to the treatment was similar in all groups. However, the reduction in cough severity was inversely related to the percentage of sputum neutrophils (r = −0.44, P = 0.003). We showed that the percentage of neutrophils in sputum >46% may be considered as a predictor of poor response to anti-asthmatic therapy.

Conclusion

The diversity of inflammatory phenotypes with paucigranulocytic preponderance was found in subjects with CVA. The response to anti-asthmatic treatment in patients with CVA was not related to the inflammatory phenotype. High neutrophil count in sputum may predict poor response to anti-asthmatic therapy in patients with CC and bronchial hyperresponsiveness.

WAO-ARIA consensus on chronic cough - Part II: Phenotypes and mechanisms of abnormal cough presentation - Updates in COVID-19

BACKGROUND

Chronic cough can be triggered by respiratory and non-respiratory tract illnesses originating mainly from the upper and lower airways, and the GI tract (ie, reflux). Recent findings suggest it can also be a prominent feature in obstructive sleep apnea (OSA), laryngeal hyperresponsiveness, and COVID-19. The classification of chronic cough is constantly updated but lacks clear definition. Epidemiological data on the prevalence of chronic cough are informative but highly variable. The underlying mechanism of chronic cough is a neurogenic inflammation of the cough reflex which becomes hypersensitive, thus the term hypersensitive cough reflex (HCR). A current challenge is to decipher how various infectious and inflammatory airway diseases and esophageal reflux, among others, modulate HCR.

OBJECTIVES

The World Allergy Organization/Allergic Rhinitis and its Impact on Asthma (WAO/ARIA) Joint Committee on Chronic Cough reviewed the current literature on classification, epidemiology, presenting features, and mechanistic pathways of chronic cough in airway- and reflux-related cough phenotypes, OSA, and COVID-19. The interplay of cough reflex sensitivity with other pathogenic mechanisms inherent to airway and reflux-related inflammatory conditions was also analyzed.

OUTCOMES

Currently, it is difficult to clearly ascertain true prevalence rates in epidemiological studies of chronic cough phenotypes. This is likely due to lack of standardized objective measures needed for cough classification and frequent coexistence of multi-organ cough origins. Notwithstanding, we emphasize the important role of HCR as a mechanistic trigger in airway- and reflux-related cough phenotypes. Other concomitant mechanisms can also modulate HCR, including type2/Th1/Th2 inflammation, presence or absence of deep inspiration-bronchoprotective reflex (lower airways), tissue remodeling, and likely cough plasticity, among others.

Characteristics of childhood allergic diseases in outpatient and emergency departments in Shanghai, China, 2016-2018: a multicenter, retrospective study

Background

The prevalence of allergic diseases (ADs), such as asthma and allergic rhinitis (AR), is increasing worldwide in both adults and children. Although ADs are common and frequently coexist in outpatient care, city-level data regarding the characteristics of childhood AD remain limited in China. This study aimed to assess the profile and characteristics of ADs in the city of Shanghai.

Methods

A multicenter retrospective study was designed to collect routine administrative data from outpatient and emergency departments from 66 hospitals in Shanghai, China, from 2016 to 2018. Children with asthma, AR, allergic conjunctivitis (AC), and allergic skin diseases were investigated. Demographic characteristics, patients visit pattern, spectrum of diagnosis, and comorbidities were analyzed.

Results

A total of 2,376,150 outpatient and emergency visits for ADs were included in the period from 2016 to 2018. Allergic skin diseases accounted for 38.9%, followed by asthma (34.8%), AR (22.9%), and AC (3.3%), with a male predominance in all four diseases. Asthma and allergic skin diseases were most frequent in the 1 to < 4 years of age group, while AR and AC were more common in the 4 to < 7 years of age group. Asthma accounted for the greatest number of annual and emergency visits. The most frequent comorbidity of asthma was lower respiratory tract infection (LRTI) (49.3%), followed by AR (20.5%) and upper respiratory tract infection (14.1%). The most common comorbidities of AR were otitis media (23.4%), adenoid hypertrophy/obstructive sleep apnea (22.1%), followed by LRTI (12.1%), asthma (9.4%) and chronic pharyngitis (8.9%).

Conclusions

Asthma and allergic skin diseases were the most common ADs in outpatient and emergency departments in the study period. Respiratory tract infection was the most common comorbidity of asthma in children. More attention should be devoted to the treatment of comorbidities to improve childhood AD outcomes with a better understanding of the characteristics of ADs in outpatient care.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-021-02880-0.

Metabolic Phenotypes in Asthmatic Adults: Relationship with Inflammatory and Clinical Phenotypes and Prognostic Implications

Bronchial asthma is a chronic disease that affects individuals of all ages. It has a high prevalence and is associated with high morbidity and considerable levels of mortality. However, asthma is not a single disease, and multiple subtypes or phenotypes (clinical, inflammatory or combinations thereof) can be detected, namely in aggregated clusters. Most studies have characterised asthma phenotypes and clusters of phenotypes using mainly clinical and inflammatory parameters. These studies are important because they may have clinical and prognostic implications and may also help to tailor personalised treatment approaches. In addition, various metabolomics studies have helped to further define the metabolic features of asthma, using electronic noses or targeted and untargeted approaches. Besides discriminating between asthma and a healthy state, metabolomics can detect the metabolic signatures associated with some asthma subtypes, namely eosinophilic and non-eosinophilic phenotypes or the obese asthma phenotype, and this may prove very useful in point-of-care application. Furthermore, metabolomics also discriminates between asthma and other “phenotypes” of chronic obstructive airway diseases, such as chronic obstructive pulmonary disease (COPD) or Asthma–COPD Overlap (ACO). However, there are still various aspects that need to be more thoroughly investigated in the context of asthma phenotypes in adequately designed, homogeneous, multicentre studies, using adequate tools and integrating metabolomics into a multiple-level approach.