Characteristics of patients with chronic cough who developed classic asthma during the course of cough variant asthma: a longitudinal study

Identification of cough-variant asthma phenotypes based on clinical and pathophysiologic data

BACKGROUND

Cough-variant asthma (CVA) may respond differently to antiasthmatic treatment. There are limited data on the heterogeneity of CVA.

OBJECTIVE

We aimed to classify patients with CVA using cluster analysis based on clinicophysiologic parameters and to unveil the underlying molecular pathways of these phenotypes with transcriptomic data of sputum cells.

METHODS

We applied k-mean clustering to 342 newly physician-diagnosed patients with CVA from a prospective multicenter observational cohort using 10 prespecified baseline clinical and pathophysiologic variables. The clusters were compared according to clinical features, treatment response, and sputum transcriptomic data.

RESULTS

Three stable CVA clusters were identified. Cluster 1 (n = 176) was characterized by female predominance, late onset, normal lung function, and a low proportion of complete resolution of cough (60.8%) after antiasthmatic treatment. Patients in cluster 2 (n = 105) presented with young, nocturnal cough, atopy, high type 2 inflammation, and a high proportion of complete resolution of cough (73.3%) with a highly upregulated coexpression gene network that related to type 2 immunity. Patients in cluster 3 (n = 61) had high body mass index, long disease duration, family history of asthma, low lung function, and low proportion of complete resolution of cough (54.1%). TH17 immunity and type 2 immunity coexpression gene networks were both upregulated in clusters 1 and 3.

CONCLUSION

Three clusters of CVA were identified with different clinical, pathophysiologic, and transcriptomic features and responses to antiasthmatics treatment, which may improve our understanding of pathogenesis and help clinicians develop individualized cough treatment in asthma.

Efficacy and Safety of Yukmijihwang-Tang in the Treatment of Cough-Variant Asthma: Study Protocol for a Phase 2, Randomized, Double-Blind, Placebo-Controlled, Multicenter Trial

BACKGROUND

Cough-variant asthma (CVA), a precursor of typical asthma, is the main cause of chronic cough. We hypothesize that yukmijihwang-tang (YJT), which has been used for chronic cough in traditional medicine and has been reported to have an anti-inflammatory effect, could be an adjuvant to asthma treatment.

METHODS

We plan a randomized, double-blind, placebo-controlled, multicenter, phase 2 trial to investigate the efficacy and safety of YJT in CVA patients. A total of 60 patients with CVA will be recruited and randomly assigned to either a high-dose YJT group, standard-dose YJT group, or control group (placebo) in a 1:1:1 allocation ratio after a 2-week run-in period. For the run-in period, only inhaled corticosteroids (ICSs) will be used, and the investigational drug will be administered once a day with concomitant ICS for 6 weeks. Data will be collected at baseline, week 3, and week 6, and the primary outcome measure will be the mean cough symptom score (CSS) change before and after medication. The secondary outcome measures will include the Leicester cough questionnaire-Korean version (LCQ-K) score, eosinophil count and eosinophil cationic protein level, pulmonary function test, and the number of uses of rescue medication, and so on.

CONCLUSION

This study aimed to evaluate the efficacy and safety of YJT in concomitant treatment with ICS in patients with CVA and to determine the optimal dosage of YJT. The results are expected to provide evidence for the use of YJT as an adjuvant treatment for CVA.

Hintergrund

Cough-Variant-Asthma (CVA), eine Frühform von typischem Asthma, ist die Hauptursache von chronischem Husten. Unserer Vermutung nach könnte Yukmijihwang-Tang (YJT), das in der traditionellen Medizin zur Behandlung von chronischem Husten eingesetzt wird und das Berichten zufolge einen entzündungshemmenden Effekt hat, unterstützend in der Asthma-Therapie wirken.

Method

en: Wir planen eine randomisierte, doppelblinde, placebokontrollierte, multizentrische Phase-2-Studie, um die Wirksamkeit und Sicherheit von YJT bei Patienten mit CVA zu untersuchen. Insgesamt werden 60 CVA-Patienten für die Studie rekrutiert und nach einer zweiwöchigen Run-in-Phase randomisiert im Verhältnis 1:1:1 einer Gruppe mit hochdosiertem YJT, einer Gruppe, die YJT in der Standarddosierung erhält oder einer Kontrollgruppe (Placebo) zugewiesen. Während der Run-in-Phase werden nur inhalative Corticosteroide (ICS) verwendet, und das Prüfpräparat wird über 6 Wochen einmal täglich gleichzeitig mit den ICS angewendet. Die Datenerhebung erfolgt bei Studienbeginn, in Woche 3 sowie in Woche 6, und das primäre Zielkriterium ist die Änderung des mittleren Hustenscores (cough symptom score, CSS) vor und nach der Anwendung der Medikamente. Zu den sekundären Zielkriterien gehören der Score des Leicester Hustenfragebogens - koreanische Version (LCQ-K), die Eosinophilenzahl und der Spiegel an eosinophilem kationischen Protein, Lungenfunktionstests sowie die Anzahl der Anwendungen von Bedarfsmedikation usw.

Schlussfolgerung

Ziel dieser Studie ist es, die Wirksamkeit und Sicherheit von YJT bei gleichzeitiger Behandlung mit ICS bei Patienten mit CVA zu bewerten und die optimale YJT-Dosis zu ermitteln. Es wird erwartet, dass die Ergebnisse Belege für die Anwendung von YJT als adjuvante Therapie bei CVA liefern werden.

Registrierung der Studie

WHO International Clinical Trials Registry Platform, Clinical Research Information Service (CRIS), KCT0006994, registriert am 10. Februar 2022, https://cris.nih.go.kr/cris/search/detailSearch.do/21743.

Prediction of bronchodilation test in adults with chronic cough suspected of cough variant asthma

Background

Many patients with cough variant asthma (CVA) are underdiagnosed and undertreated due to the atypical symptoms, low diagnostic sensitivity of bronchodilator response (BDR), and limited application of bronchial challenge test.

Objective

To investigate whether airway reversibility in BDR can predict CVA diagnosis in patients with chronic cough and negative BDR.

Methods

This open-label, prospective cohort study included patients with chronic cough, nearly normal chest CT scan, and negative BDR results. Inhaled corticosteroids and long-acting β₂ agonists were given for 4 weeks. The confirmed diagnosis of CVA was defined as improved symptoms and an increase of forced expiratory volume in 1 s (FEV₁) by >12% and >200 mL after 4 weeks of treatment.

Results

Of 155 patients recruited, 140 completed the study. Patients in the CVA positive diagnosis group had greater absolute (Δ) and percent (Δ%) improvements in FEV₁ and forced expiratory flows (FEFs), and higher fractional exhaled nitric oxide (FENO) than in the CVA negative diagnosis group. The area under the receiver operating characteristic curves (AUCs) of ΔFEV₁%, FEF_25-75%pred (percentage of predicted forced expiratory flow at 25% to 75%) and FENO for CVA positive diagnosis was 0.825, 0.714, and 0.637, with cutoff values of 5.90%, 61.99% and 41.50 ppb, respectively. A joint model of ΔFEV₁% combined with FEF_25-75%pred or FENO increased the AUC to 0.848 and 0.847, respectively.

Conclusion

ΔFEV₁% in BDR can predict a CVA diagnosis and response to anti-asthma treatment in patients with chronic cough and negative BDR.

Clinical trial registration

[http://www.chictr.org.cn/index.aspx], identifier [ChiCTR2000029065].

Wide-Bandwidth Nanocomposite-Sensor Integrated Smart Mask for Tracking Multiphase Respiratory Activities

Wearing masks has been a recommended protective measure due to the risks of coronavirus disease 2019 (COVID-19) even in its coming endemic phase. Therefore, deploying a "smart mask" to monitor human physiological signals is highly beneficial for personal and public health. This work presents a smart mask integrating an ultrathin nanocomposite sponge structure-based soundwave sensor (≈400 µm), which allows the high sensitivity in a wide-bandwidth dynamic pressure range, i.e., capable of detecting various respiratory sounds of breathing, speaking, and coughing. Thirty-one subjects test the smart mask in recording their respiratory activities. Machine/deep learning methods, i.e., support vector machine and convolutional neural networks, are used to recognize these activities, which show average macro-recalls of ≈95% in both individual and generalized models. With rich high-frequency (≈4000 Hz) information recorded, the two-/tri-phase coughs can be mapped while speaking words can be identified, demonstrating that the smart mask can be applicable as a daily wearable Internet of Things (IoT) device for respiratory disease identification, voice interaction tool, etc. in the future. This work bridges the technological gap between ultra-lightweight but high-frequency response sensor material fabrication, signal transduction and processing, and machining/deep learning to demonstrate a wearable device for potential applications in continual health monitoring in daily life.

Mechanism of Action of Yin Nourishing and Heat Clearing Prescription in Treating Cough Variant Asthma Based on Network Pharmacology and Molecular Docking Verification

Objective. To explore the mechanism of action of the yin nourishing and heat clearing prescription in treating cough variant asthma (CVA) based on network pharmacology (NP). Methods. The active ingredients and targets of the yin nourishing and heat clearing prescription were screened using the Traditional Chinese Medicine System Pharmacology Analysis Platform (TCMSP); CVA targets were screened by the GeneCards, NCBI gene, and OMIM databases to construct the component-target network and the protein-protein interaction (PPI) network. GO functional enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of the target genes were performed to construct the component-disease-pathway-target biological network. Moreover, CVA-related core target structures with high values were subjected to molecular docking (MD) with the active components. Results. We found 265 eligible targets in the prescription and 1115 CVA-related genes. The medicine targets were intersected with disease targets, which yielded 148 common targets. After topology analysis, 66 key targets were screened. Upon GO functional annotation, 2408 biological processes, 153 molecular functions, and 162 KEGG pathways were enriched. Molecular docking results suggested that the major active ingredients of the prescription showed high affinity to the key targets, among which AKT1 might be the most important target. Conclusions. Active ingredients might act on AKT1, IL-6, VEGFA, IL-1B, and JUN to suppress eosinophil accumulation, decrease histamine release, suppress airway inflammation, regulate the airway immune microenvironment, increase autophagy in lung tissue, inhibit mucus production, and reduce airway resistance and hyperresponsiveness, thus treating CVA. Our findings provide a reference for further research and clinical applications of the prescription.

Retrospective Study of the Effects of Post-nasal Drip Symptoms on Cough Duration

BACKGROUND/AIM

The aim of this study was to elucidate the significance of allergic rhinitis and post-nasal drip symptoms in patients with cough-variant and cough-predominant asthma.

PATIENTS AND METHODS

We conducted a retrospective analysis of 91 patients who had cough-variant or cough-predominant asthma and first visited the Nakajima Medical Clinic in Japan between June 2012 and July 2015.

RESULTS

Post-nasal drip symptoms were reported in 58 (63.7%) patients. The patients with post-nasal drip symptoms (19.5±8.3 days) had a significantly longer time until cough disappearance than those without post-nasal drip symptoms (11.0±4.8 days) (p=0.000034). Multivariate analysis showed that post-nasal drip symptoms are independent prolonged factors of cough duration.

CONCLUSION

Post-nasal drip symptoms may affect cough control in patients with cough-variant and cough-predominant asthma.

Isolated night cough in children: how does it differ from wheeze?

It has been postulated that some children with recurrent cough but no wheeze have a mild form of asthma (cough variant asthma), with similar risk factors and an increased risk of future wheeze.

This longitudinal study compared risk factors for isolated night cough and for wheeze in the Leicester Respiratory Cohort in children aged 1, 4, 6 and 9 years and compared prognosis of children with isolated night cough, children with wheeze and asymptomatic children.

We included 4101 children aged 1 year, 2854 aged 4 years, 2369 aged 6 years and 1688 aged 9 years. The prevalence of isolated night cough was 10% at age 1 year and 18% in older children. Prevalence of wheeze decreased from 35% at 1 year to 13% at 9 years. Although several risk factors were similar for cough and wheeze, day care, reflux and family history of bronchitis were more strongly associated with cough, and male sex and family history of asthma with wheeze. Over one-third of preschool children with cough continued to cough at school age, but their risk of developing wheeze was similar to that of children who were asymptomatic at earlier surveys. Wheeze tracked more strongly throughout childhood than cough.

In conclusion, our study showed that only some risk factors for cough and wheeze were shared but many were not, and there was little evidence for an increased risk of future wheeze in children with isolated night cough. This provides little support for the hypothesis that recurrent cough without wheeze may indicate a variant form of asthma.

Children with isolated night cough do not have an increased risk of future wheeze, and risk factors for cough and wheeze only partially overlap.https://bit.ly/31IbXSC

Repeated bronchoconstriction attenuates the cough response to bronchoconstriction in naïve guinea pigs

BACKGROUND

Cough variant asthma (CVA) is recognized as a precursor of bronchial asthma (BA). However, the cough response to bronchoconstriction differs between these similar diseases. Repeated bronchoconstriction and the resulting imbalance of endogenous lipid mediators may impact the cough response.

METHODS

We investigated the influence of repeated bronchoconstriction on the cough response to bronchoconstriction using naïve guinea pigs. Bronchoconstriction was induced for 3 consecutive days and changes in the cough response and lipid mediators, such as PGE₂, PGI₂, and cysteinyl-LTs (Cys-LTs), in BAL fluid (BALF) were assessed. We investigated the effect of endogenous PGI₂ on the cough response by employing a PGI₂ receptor antagonist. In order to investigate the cough response over a longer period, we re-evaluated the cough response 2 weeks after repeated bronchoconstriction.

RESULTS

The number of coughs induced by bronchoconstriction were significantly decreased by repeated bronchoconstriction. The levels of PGE₂, PGI₂, and Cys-LTs, and the ratio of PGI₂/PGE₂ were significantly increased, following repeated bronchoconstriction. This decrease in the cough response was suppressed by pretreatment with a PGI₂ receptor antagonist. Two weeks after repeated bronchoconstriction, the cough response returned to the same level as before repeated bronchoconstriction along with a concomitant return of lipid mediators, such as PGE₂, PGI₂, and Cys-LTs and the ratio of PGI₂/PGE₂.

CONCLUSIONS

Our results suggest that repeated bronchoconstriction and the resulting imbalance of endogenous lipid mediators contribute to the difference in cough responses to bronchoconstriction in CVA and BA.

Role and Impact of Chronic Cough in Individuals with Asthma From the General Population

BACKGROUND

Cough is a well-recognized symptom in asthma, but the role and impact of chronic cough in individuals with asthma has not been described in the general population.

OBJECTIVE

We hypothesized that among individuals with asthma, those with chronic cough versus those without have a more severe disease phenotype.

METHODS

We identified individuals with asthma and chronic cough among 14,740 adults from the Copenhagen General Population Study, and investigated respiratory symptoms, health care utilizations, lung function, and biomarkers in blood.

RESULTS

A total of 855 (6%) individuals suffered from asthma, and 70 (8%) had chronic cough. Individuals with asthma and chronic cough had a Leicester Cough Questionnaire median total score of 16.8 (25th and 75th percentiles, 14.8-18.9), corresponding to 5.4 (4.6-6.0) for the physical domain, 5.7 (4.6-6.4) for the psychological domain, and 6.0 (5.3-6.8) for the social domain. Among individuals with asthma, those with chronic cough versus those without reported more often wheezing (70% vs 54%), dyspnea (74% vs 49%), night-time dyspnea (27% vs 11%), sputum production (59% vs 14%), chest pain/tightness (14% vs 4%), acute bronchitis/pneumonia episodes, and general practitioner visits. Furthermore, these individuals had more often FEV₁ predicted value of less than 60% (14% vs 7%) and higher levels of neutrophils, leukocytes, and fibrinogen in blood, but there were no differences with regard to levels of high-sensitive C-reactive protein, eosinophils, and IgE in blood.

CONCLUSIONS

Chronic cough in individuals with asthma is associated with a more severe disease phenotype in terms of worse respiratory symptoms, greater health care utilizations, lower lung function, and higher levels of systemic inflammatory biomarkers in blood.

A breath sound analysis in children with cough variant asthma

BACKGROUND

Cough variant asthma (CVA) is characterized by a chronic cough and bronchial hyperresponsiveness without confirmation of wheezing. Using a breath sound analyzer, we evaluate the characteristics of breath sound in children with CVA.

METHODS

Nine children with CVA (median age, 7.0 years) participated. The existence of breath sounds was confirmed by sound spectrogram. Breath sound parameters, the frequency limiting 50% and 99% of the power spectrum (F₅₀ and F₉₉), the roll-off from 600 to 1200 Hz (Slope) and spectrum curve indices, the ratio of the third and fourth area to the total area of the power spectrum (P₃/P_T and P₄/P_T) and the ratio of power and frequency at 50% and 75% of the highest frequency of the power spectrum (RPF₇₅ and RPF₅₀) were calculated before and after β₂ agonist inhalation. A spirogram and/or forced oscillation technique were performed in all subjects.

RESULTS

On a sound spectrogram, wheezing was confirmed in seven of nine patients. All wheezing on the image was polyphonic, and they almost disappeared after β₂ agonist inhalation. An analysis of the breath sound spectrum showed that P_T, P₃/P_T, P₄/P_T, RPF₅₀ and RPF₇₅ were significantly increased after β₂ agonist inhalation.

CONCLUSIONS

Children with CVA showed a high rate of inaudible wheezing that disappeared after β₂ agonist inhalation. Changes in the spectrum curve indices also indicated the bronchial reversibility. These results may suggest the characteristics of CVA in children.

Therapeutic Effects of Kangzhi Syrup in a Guinea Pig Model of Ovalbumin-Induced Cough Variant Asthma

Purpose

This study aimed to investigate the possible effects and underlying mechanisms of Kangzhi syrup on ovalbumin- (OVA-) induced cough variant asthma (CVA) in guinea pigs.

Methods

All 48 guinea pigs were randomly assigned to four experimental groups: normal, OVA model with or without Kangzhi syrup (OVA and OVA + KZ), and OVA with Dexamethasone (OVA + DM). After sensitizing the guinea pigs, a cough challenge was performed by the inhalation of capsaicin. The antitussive effect, inflammatory cells, cytokines in bronchoalveolar lavage fluid (BALF) and lung tissue, and morphological changes were examined.

Results

Compared with model group, Kangzhi syrup effectively exerted an antitussive effect (p < 0.0001) and reduced the pneumonic anaphylacticitis by inhibiting the infiltration of total inflammatory cells (p < 0.0001) and reducing the percentage of eosinophil in BALF (p < 0.0001). Moreover, evidence from morphological studies also demonstrated that Kangzhi syrup inhibited the infiltration of inflammatory cells and ameliorated the structure changes. NF-κB and TGF-β1 expression were attenuated in the OVA + KZ group versus the OVA group (p < 0.0001). Additionally, a semiquantitative analysis of TGF-β1 expression also demonstrated that the Kangzhi syrup attenuated this profibrogenic growth factor (p < 0.001).

Conclusions

The results demonstrated that Kangzhi syrup exerted a considerable antitussive effect in CVA animal model, which depended on its marked impact on the anti-anaphylactic inflammation. Additionally, it could ameliorate the airway remodeling by inhibiting NF-κB and TGF-β1 signal pathway.

Fractional exhaled nitric oxide levels as a predictor of long-term prognoses in patients with mild asthma

BACKGROUND

There is a growing belief that patients with bronchial asthma (BA) should be provided an individualized and optimized treatment plan. We aimed to clarify the predictors of long-term prognoses in patients with mild BA.

METHODS

We conducted a retrospective study of consecutive patients who were newly diagnosed with mild BA at Iwate Medical University from 2011 to 2013, focusing on achievement of full asthma control based on the Asthma Control Test as an indicator of prognosis. Predictors were identified on the basis of a chart review.

RESULTS

Among 71 patients with mild BA, 37 patients completed regular clinic visits for 1 year. Nineteen (51.4%) of these patients achieved full asthma control. Current smoking and the fractional exhaled nitric oxide (FeNO) level at the first patient visit were identified by multivariate logistic regression as possible predictors of the discontinuation of clinic visits and achievement of full asthma control, respectively. Low FeNO levels at the first clinic visit yielded a receiver operating characteristic-area under the curve of 0.860 (95% confidence interval [CI]=0.774-0.975) for the achievement of full asthma control. Using an FeNO cut-off level of 34 parts per billion yielded a sensitivity of 76.5% (95% CI=59.5-88.2%) and specificity of 73.7% (95% CI=58.5-84.2%).

CONCLUSION

Our preliminary results suggested that patients with newly diagnosed mild BA who display higher FeNO levels at their first clinic visits should be appropriately educated during early visits to receive optimal treatment and complete regular clinic visits.

Cough variant asthma patients are more depressed and anxious than classic asthma patients

OBJECTIVE

Many recent studies have indicated that depression and anxiety are more common in asthmatic patients than in the general population and psychological stress can lead to asthma exacerbations, but no study specifically targets cough variant asthma (CVA) patients. The purpose of this study was to evaluate depression and anxiety levels in CVA patients compared with classic asthma patients and to identify the psychological features of CVA patients.

METHODS

Fifty-nine outpatients with CVA and 128 outpatients with classic asthma were interviewed about psychosomatic and psychiatric symptoms, and they underwent three psychological tests: Self-rating Depression Scale (SDS), State-Trait Anxiety Inventory (STAI), and Comprehensive Asthma Inventory (CAI). They were ultimately screened for major and minor depression, dysthymia, panic disorder, generalized anxiety disorder, social anxiety disorder, and other anxiety disorders.

RESULTS

CVA patients showed higher SDS and STAI scores than classic asthma patients, and mood disorders and anxiety disorders were more common than in classic asthma outpatients. The psychological factors 'frustration', 'fright into illness', and 'distorted lifestyle' were more prominent in CVA patients than in classic asthma patients.

CONCLUSION

CVA patients are on average more depressed and anxious than classic asthma outpatients. Though CVA appears pathologically to be just an early stage of typical asthma, the psychological stress may often be more serious than in asthma controlled by medication, which may explain why CVA cannot be controlled by a bronchodilator alone and patients often require no less intense therapy than for severe asthma.

Clinical study on treatment of cough variant asthma by Chinese medicine

OBJECTIVE

To observe the clinical efficacy and the change of airway responsiveness to Chinese medicine (CM) in treating cough variant asthma (CVA).

METHODS

Ninety-four patients who had confirmed the diagnosis of CVA were selected and randomly assigned to the treatment group and the control group by the blocked randomization method. The ratio of the two groups was 2:1. The treatment group had 63 patients that were treated by CM, lost in 10 cases, 53 patients had finished the trial. The control group had 31 patients that were treated by montelukast tablets and theophylline, lost in 5 cases, 26 patients had finished the trial, two weeks as one therapeutic course. The syndrome efficacy, cough efficacy, symptom score and the airway responsiveness between two groups were observed.

RESULTS

The comparison of the syndrome efficacy: the total effective rate of the treatment group was 90.57% and the control group was 76.92%, and the two groups were significantly different (P<0.05). The comparison of the cough efficacy: the total effective rate of the treatment group was 98.11% and the control group was 80.77%, and the two groups were also significantly different (P<0.05). Syndrome scoring and cough scoring were all significantly lowered, but the airway responsiveness was not significantly lowered.

CONCLUSIONS

The treatment of CM could ease the cough, improve the syndrome, and shows obvious advantages compared with the control group, which is worthy of extensive clinical application.

Efficacy and safety of modified sequential three-step empirical therapy for chronic cough

BACKGROUND AND OBJECTIVE

Sequential three-step empirical therapy is useful for the management of chronic cough. The purpose of this study was to evaluate the efficacy and safety of modified sequential three-step empirical therapy.

METHODS

Consecutive patients (n = 240) with chronic cough were recruited and randomly assigned to receive modified (modified group) or primary (primary group) sequential three-step empirical therapy. The primary end-point was the overall rate of control of chronic cough. Secondary end-points were the rate of control of chronic cough at each step of therapy, the duration of treatment required, changes in cough symptom score, health-related quality of life and possible adverse effects.

RESULTS

The study was completed by 106 patients in the modified group and 108 patients in the primary group. The overall rate of control of chronic cough was 88.7% in the modified group and 91.7% in the primary group (chi(2) = 0.54, P > 0.05). There were no obvious differences in the rate of control of cough at each step of therapy, the duration of treatment required, patterns of cough symptom scores or improvements in the health-related quality of life between the modified and primary groups. However, the incidence of drowsiness was significantly lower in the modified group than in the primary group (11.7% vs 21.7%, chi(2) = 4.32, P = 0.04).

CONCLUSIONS

Modified three-step empirical therapy was as efficacious as primary three-step therapy for chronic cough, but was preferable because it had fewer side-effects.

Eosinophilic airway disorders associated with chronic cough

Chronic cough is a major clinical problem. The causes of chronic cough can be categorized into eosinophilic and noneosinophilic disorders, the former being comprised of asthma, cough variant asthma (CVA), atopic cough (AC) and non-asthmatic eosinophilic bronchitis (NAEB). Cough is one of the major symptoms of asthma. Cough in asthma can be classified into three categories; 1) CVA: asthma presenting solely with coughing, 2) cough-predominant asthma: asthma predominantly presenting with coughing but also with dyspnea and/or wheezing, and 3) cough remaining after treatment with inhaled corticosteroid (ICS) and beta2-agonists in patients with classical asthma, despite control of other symptoms. There may be two subtypes in the last category; one is cough responsive to anti-mediator drugs such as leukotriene receptor antagonists and histamine H1 receptor antagonists, and the other is cough due to co-morbid conditions such as gastroesophageal reflux. CVA is one of the commonest causes of chronic isolated cough. It shares a number of pathophysiological features with classical asthma with wheezing such as atopy, airway hyperresponsiveness (AHR), eosinophilic airway inflammation and various features of airway remodeling. One third of adult patients may develop wheezing and progress to classical asthma. As established in classical asthma, ICS is considered the first-line treatment, which improves cough and may also reduce the risk of progression to classical asthma. AC proposed by Fujimura et al. presents with bronchodilator-resistant dry cough associated with an atopic constitution. It involves eosinophilic tracheobronchitis and cough hypersensitivity and responds to ICS treatment, while lacking in AHR and variable airflow obstruction. These features are shared by non-asthmatic eosinophilic bronchitis (NAEB). However, atopic cough does not involve bronchoalveolar eosinophilia, has no evidence of airway remodeling, and rarely progresses to classical asthma, unlike CVA and NAEB. Histamine H1 antagonists are effective in atopic cough, but their efficacy in NAEB is unknown. AHR of NAEB may improve with ICS within the normal range. Taken together, NAEB significantly overlaps with atopic cough, but might also include milder cases of CVA with very modest AHR. The similarity and difference of these related entities presenting with chronic cough and characterized by airway eosinophilia will be discussed.

Pharmacotherapy of cough-variant asthma

Cough-variant asthma is considered as an asthma subset in which chronic cough is the only symptom. It is believed to be more frequent and, hence, sometimes overdiagnosed in children, and shares with typical asthma eosinophilic airway inflammation and consequent bronchial hyper-responsiveness. Presently available therapies consist of bronchodilators, inhaled or oral corticosteroids, or leukotriene modifiers. However, the long-term efficacy of these agents in adults and children is not known. This review focuses on current therapies used for cough variant asthma, also highlighting potential therapeutic targets for this condition.

The relationship between psychogenic cough and the diagnosis and misdiagnosis of asthma: a review

The differential diagnoses of persistent nonproductive cough include numerous pulmonary and nonpulmonary organic disorders as well as functional illnesses. Many diseases can cause cough, and several studies have shown asthma among the most common etiologies associated with chronic cough in adult nonsmokers, as well as children. Psychogenic cough and its relationship to asthma and other asthma-like illnesses is complex since distinct maladies with similar features may coexist individually or in combination in any given patient. While chronic cough may occur as a sole presenting manifestation of bronchial asthma in all age groups, recent findings suggest that most children with persistent cough without other respiratory symptoms do not have asthma. Since several organic, as well as functional diseases, may present with persistent cough as their sole manifestation in either adults or children, cough should not be used as a single or major determinant to diagnose and treat asthma, especially when empirically focused therapy trials fail. Given the range of illnesses causing cough, no single management guideline can be expected to be universally effective.

Cough and asthma

PURPOSE OF REVIEW

The intention of this article is to discuss and place into perspective recent articles on cough and asthma.

RECENT FINDINGS

Asthma continues to be a major diagnosis in most studies of cough. The first prospective study of sub-acute cough demonstrated an asthma incidence lower than that for chronic cough, a logical finding; upper airway cough syndrome often causes cough in the postinfectious state. The first prospective study of cough in infants suggested asthma to be a minor cause of cough in infants, but methodological flaws make the conclusions uncertain. Efforts to separate cough-variant asthma from classic asthma continue. One group has demonstrated that the maximal bronchoconstrictor response in cough-variant asthma is blunted when compared with classic asthma, a possible explanation for the absence of wheeze and dyspnea in cough-variant asthma. Another look at airway resistance showed a less rapid rate of rise in resistance in cough-variant asthma with increasing methacholine dosing than in classic asthma. On the biochemical front, a group has demonstrated differences in vascular endothelial growth factor, which may be the underpinnings of differences between cough-variant asthma and classic asthma.

SUMMARY

Recent data suggest that cough-variant asthma is part of a continuum in the expression of asthma symptoms and in the asthmatic inflammatory response.

Cough sensitivity in pure cough variant asthma elicited using continuous capsaicin inhalation

BACKGROUND

Cough variant asthma has recently been described, mainly as airway inflammation in relation to bronchial asthma, but the relationship between the two types of asthma remains unclear. Further studies of cough receptor sensitivity are necessary to fully characterize cough variant asthma.

METHODS

We assessed the relevance of testing cough sensitivity using an Astograph with continuous capsaicin inhalation, and compared the results with those obtained using intermittent inhalation. We showed the clinical applicability of testing cough sensitivity (0.156-80 microM capsaicin; five or more coughs, 1 minute of continuous inhalation at each concentration) using this method. We compared cough sensitivity among patients with pure cough variant asthma who did not develop bronchial asthma after an observation period of at least 1 year, patients with bronchial asthma and healthy individuals.

RESULTS

The continuous cough sensitivity test using the Astograph was reproducible and reliable. Cough sensitivity in patients with pure cough variant asthma was significantly higher than that in healthy individuals.

CONCLUSIONS

The cough sensitivity of patients with cough variant asthma is not necessarily identical to that of healthy individuals.