Indirect challenge tests: Airway hyperresponsiveness in asthma: its measurement and clinical significance

Thoracic Society of Australia and New Zealand position statement: The safe clinical use of sputum induction for bio-sampling of the lower airways in children and adults

Sputum induction is widely used in clinical settings for collection of biological samples from the lower airways. However, in recent years sputum induction has been associated with serious adverse events and even death. This position statement was commissioned by the Thoracic Society of Australia and New Zealand to address major adverse events of two deaths associated with sputum induction that have occurred in Australia in 2021, and outlines best practice for the safe use of sputum induction. The statement resulted from systematic literature searches by a multi-disciplinary group including respiratory physicians, nurses and physiotherapists (paediatric and adults focused). Consumers had input to an advanced draft of the position statement. The position statement covers indications for sputum induction, informed consent, scope of practice of personnel administering the procedure, infection control considerations, details about the sputum induction procedure, safety considerations and risk assessment in clinical settings.

What is the Best Way to Diagnose Possible Asthma Patients with Negative Bronchodilator Reversibility Tests?

Objective

The best method and strategy for the diagnosis of asthma remains unclear, especially in patients with negative bronchodilator reversibility test (BDRT). In our study, we aimed to investigate the diagnostic yield of peak expiratory flow (PEF) variability for this patient group.

Methods

A total of 50 patients with suspected asthma, all with negative BDR test, were included in the study. Demographic information and symptoms were recorded and PEF variability was monitored for 2 weeks. Metacolinbronchial provocation test (mBPT) was performed. Asthma was diagnosed when PEF variability ≥20% and/or positive mBPT was observed.

Results

30 of 50 patients were diagnosed with asthma. After 1 month, 17 patients were evaluated for treatment outcomes. The sensitivity and specificity of PEF variability for different cut-off values (≥20%, >15% and >10%) were 61.5-83.3, 88.5-62.5 and 100-16.7, respectively. One of the most important findings of our study was the absence of variable airflow limitation or airway hyper reactivity in 39% patients with a previous diagnosis of asthma. Multiple logistic regression analysis revealed that a low baseline FEF25-75 value was an independent predictive factor for the diagnosis of asthma (p= 0.05).

Conclusion

The most efficient diagnostic test for asthma is still unclear due to many factors. Our study is one of the few studies on this subject. Although current diagnostic recommendations generally recommend a PEF variability of 10% for the diagnosis of asthma, this threshold may not be appropriate for the BDR-negative patient group. Our results suggest using a threshold value of <15% for PEF variability when excluding asthma and ≥20% when confirming the diagnosis of asthma in patients with clinically suspected but unproven reversibility. Furthermore, FEF25-75 is considered to be an important diagnostic parameter that should be included in diagnostic recommendations for asthma.

The role of bronchial challenge test in guiding therapy in preschool children with atypical recurrent respiratory symptoms

OBJECTIVE

This retrospective observational cohort study aimed to assess the real-life application of bronchial challenge test (BCT) in the management of preschool children presenting with atypical recurrent respiratory symptoms (ARRS).

METHODS

We included children aged 0.5-6 years referred to a pediatric-pulmonology clinic who underwent BCT using methacholine or adenosine between 2012 and 2018 due to ARRS. BCT was considered positive based on spirometry results and/or wheezing, desaturation, and tachypnea reactions. We collected data on demographics, BCT results, pre-BCT and post-BCT treatment changes, and 3-6 months post-BCT compliance and symptom control. The primary outcome measure was the change in treatment post-BCT (step-up or step-down).

RESULTS

A total of 228 children (55% males) with a mean age of 4.2 ± 0.6 years underwent BCT (52% adenosine-BCT, 48% methacholine-BCT). Children referred for methacholine were significantly younger compared with adenosine (3.6 ± 1.2 vs. 4.2 ± 1.2 years, p < .01). Methacholine and adenosine BCTs were positive in 95% and 61%, respectively. Overall, changes in management were observed in 122 (53.5%) children following BCT, with 83 (36.4%) being stepped up and 37 (17%) being stepped down. Significantly more children in the methacholine group were stepped up compared with the adenosine group (46% vs. 28%, p = .004). During the follow-up assessment, we observed a clinical improvement in 119/162 (73.4%) of the children, with nearly 87% being compliant.

CONCLUSION

This study demonstrates the importance of BCT in the management of preschool children presenting to pediatric pulmonary units with ARRS. The change in treatment and subsequent clinical improvement observed highlight the added value of BCT to the pulmonologist.

Asthma and exercise-induced bronchoconstriction in athletes: Diagnosis, treatment, and anti-doping challenges

Athletes often experience lower airway dysfunction, such as asthma and exercise-induced bronchoconstriction (EIB), which affects more than half the athletes in some sports, not least in endurance sports. Symptoms include coughing, wheezing, and breathlessness, alongside airway narrowing, hyperresponsiveness, and inflammation. Early diagnosis and management are essential. Not only because untreated or poorly managed asthma and EIB potentially affects competition performance and training, but also because untreated airway inflammation can result in airway epithelial damage, remodeling, and fibrosis. Asthma and EIB do not hinder performance, as advancements in treatment strategies have made it possible for affected athletes to compete at the highest level. However, practitioners and athletes must ensure that the treatment complies with general guidelines and anti-doping regulations to prevent the risk of a doping sanction because of inadvertently exceeding specified dosing limits. In this review, we describe considerations and challenges in diagnosing and managing athletes with asthma and EIB. We also discuss challenges facing athletes with asthma and EIB, while also being subject to anti-doping regulations.

Relationship between early life asthma and chronic airway disease in adult life - in search for disease trajectories over the life span- the RELATE study based on the Kongsberg cohort

BACKGROUND

Chronic airway disease in adults may have its origin in early life. The purpose of this study is to investigate the long-term prognosis of severe childhood asthma in search for an association between asthma in early life and obstructive lung disease in adulthood.

METHODS

This study is based on the Kongsberg cohort, which includes approximately 5000 children with severe asthma with a 4-month stay at the asthma care facility in Kongsberg, Norway during the years 1950 to 1979. An on average 60-year observational study based on a follow-up examination will be performed including questionnaires, blood samples, and tests of lung function and bronchial responsiveness. Blood samples will be stored in a biobank. In addition, we will conduct further analyses of the cohort based on nationwide register data, including socio-economic parameters and mortality.

DISCUSSION

Chronic airway disease is associated with substantial burden for both the individual patient and society. Our knowledge of early life origins of chronic airway disease later in life has been increasing in recent decades but is still limited. By exploring early life risk factors for chronic airway disease in adulthood, we may gain insights paving the way for future reduction in the burden of chronic airway diseases.

Fat mass index and airway hyperresponsiveness in Korean adults

OBJECTIVE

Airway hyperresponsiveness (AHR) is associated with asthma and obesity, which is defined as a high body mass index. Body mass mainly comprises fat mass (FM) and muscle mass (MM), which are independent of each other. We investigated the effect of changes in FM over time on the development of asymptomatic AHR in adults.

METHODS

This long-term longitudinal study included adults who were underwent health checkups at the Seoul National University Hospital Gangnam Center. The participants underwent two methacholine bronchial provocation tests with a follow-up period (between the first and second tests) of more than 3 years and bioelectrical impedance analysis (BIA) at all visits. FM index (FMI; FM normalized for height) and MM index (MMI; MM normalized for height) were calculated using BIA.

RESULTS

The study included 328 adult participants (61 women and 267 men). The mean number of BIA measurements was 6.96 and the follow-up duration was 6.69 years. In total, 13 participants showed a positive conversion of AHR. Multivariate analysis indicated that a high rate of change in FMI ([g/m²]/year), not MMI, was significantly associated with the risk of AHR development (P = 0.037) after adjustment for age, sex, smoking status, and FEV1 predicted.

CONCLUSION

A rapid gain of FM over time may be a risk factor for developing AHR in adults. Prospective studies are needed to confirm our results and evaluate the role of FM reduction in preventing AHR development in obese adults.

Efficacy of biologic therapy on airway hyperresponsiveness in asthma

Airway hyperresponsiveness refers to an exaggerated bronchial constrictor response to a given exogenous inhaled agent and is governed by airway smooth muscle along with mucosal inflammation in asthma. In recent years, the advent of biologics and antialarmins has transformed severe asthma treatment in terms of reducing oral-corticosteroid-requiring exacerbations and improving disease control, asthma quality of life, and spirometry-measured lung function. In contrast, there have been comparatively fewer studies investigating the efficacy of biologics in airway hyperresponsiveness. In this focused review, we summarize the existing evidence base in this area regarding omalizumab, mepolizumab, benralizumab, and tezepelumab.

Cut-off value for exercise-induced bronchoconstriction based on the features of the airway obstruction

The current cut-off value for diagnosing exercise-induced bronchoconstriction (EIB) in adults—percent fall in FEV₁ (ΔFEV₁) ≥ 10% after exercise challenge test (ECT)—has low specificity and weak evidences. Therefore, this study aimed to identify the cut-off value for EIB that provides the highest diagnostic sensitivity and specificity. Participants who underwent the ECT between 2007 and 2018 were categorized according to ΔFEV₁: definite EIB (ΔFEV₁ ≥ 15%), borderline (10% ≤ ΔFEV₁ < 15%), and normal (ΔFEV₁ < 10%). Distinct characteristics of the definite EIB group were identified and explored in the borderline EIB group. A receiver operating characteristic curve was plotted to determine the optimal cut-off value. Of 128 patients, 60 were grouped as the definite EIB group, 23 as the borderline group, and 45 as the normal group. All participants were men, with a median age of 20 years (interquartile range [IQR:] 19–23 years). The definite EIB group exhibited wheezing on auscultation (P < 0.001), ΔFEV₁/FVC ≥ 10% (P < 0.001), and ΔFEF_25–75% ≥ 25% (P < 0.001) compared to other groups. Eight (8/23, 34.8%) patients in the borderline group had at least one of these features, but the trend was more similar to that of the normal group than the definite EIB group. A cut-off value of ΔFEV₁ ≥ 13.5% had a sensitivity of 98.5% and specificity of 93.5% for EIB. Wheezing on auscultation, ΔFEV₁/FVC ≥ 10%, and ΔFEF_25–75% ≥ 25% after ECT may be useful for the diagnosis of EIB, particularly in individuals with a ΔFEV₁ of 10–15%. For EIB, a higher cut-off value, possibly ΔFEV₁ ≥ 13.5%, should be considered as the diagnostic criterion.

The use of the mannitol test as an outcome measure in asthma intervention studies: a review and practical recommendations

BACKGROUND

The mannitol test is an indirect bronchial challenge test widely used in diagnosing asthma. Response to the mannitol test correlates with the level of eosinophilic and mast cell airway inflammation, and a positive mannitol test is highly predictive of a response to anti-inflammatory treatment with inhaled corticosteroids. The response to mannitol is a physiological biomarker that may, therefore, be used to assess the response to other anti-inflammatory treatments and may be of particular interest in early phase studies that require surrogate markers to predict a clinical response. The main objectives of this review were to assess the practical aspects of using mannitol as an endpoint in clinical trials and provide the clinical researcher and respiratory physician with recommendations when designing early clinical trials.

METHODS

The aim of this review was to summarise previous uses of the mannitol test as an outcome measure in clinical intervention studies. The PubMed database was searched using a combination of MeSH and keywords. Eligible studies included intervention or repeatability studies using the standard mannitol test, at multiple timepoints, reporting the use of PD₁₅ as a measure, and published in English.

RESULTS

Of the 193 papers identified, 12 studies met the inclusion criteria and data from these are discussed in detail. Data on the mode of action, correlation with airway inflammation, its diagnostic properties, and repeatability have been summarised, and suggestions for the reporting of test results provided. Worked examples of power calculations for dimensioning study populations are presented for different types of study designs. Finally, interpretation and reporting of the change in the response to the mannitol test are discussed.

CONCLUSIONS

The mechanistic and practical features of the mannitol test make it a useful marker of disease, not only in clinical diagnoses, but also as an outcome measure in intervention trials. Measuring airway hyperresponsiveness to mannitol provides a novel and reproducible test for assessing efficacy in intervention trials, and importantly, utilises a test that links directly to underlying drivers of disease.

The Usefulness of FEF25-75 in Predicting Airway Hyperresponsiveness to Mannitol

Background and Objective

Despite the usefulness of airway hyperresponsiveness (AHR) testing in diagnosing and monitoring asthma, it is challenging to perform in a real-world setting. Forced expiratory flow between 25% and 75% of vital capacity (FEF_25-75), a pulmonary measurement that can be obtained easily during routine spirometry, represents the status of medium-sized and small airways. However, the performance of FEF_25-75 in predicting AHR has not been well elucidated. Therefore, we investigated whether FEF_25-75 can predict AHR to mannitol.

Methods

We performed a retrospective cohort study of 428 patients who visited a single clinic due to cough, wheezing, or dyspnea. All patients underwent spirometry with a mannitol provocation test. We compared the area under the curve (AUC) of the percentage of the predicted values of FEF_25-75 (FEF_25-75 %pred) with that of forced expiratory volume in 1 second (FEV₁%pred), FEV₁/forced vital capacity (FVC), and FEF_25-75/ FVC for predicting AHR.

Results

The rate of AHR to mannitol was 20.3%. In the overall study population, the AUC of FEF_25-75 %pred for predicting AHR (0.772; 95% confidence interval [CI], 0.729-0.811) was significantly higher than that of FEV₁%pred (0.666; 95% CI, 0.619-0.710; p < 0.001), FEV₁/FVC (0.741; 95% CI, 0.697-0.782; p = 0.047), and FEF_25-75/FVC (0.741, 95% CI = 0.696-0.782, p = 0.046). The sensitivity, specificity, positive predictive value, and negative predictive value of FEF_25-75 %pred <81% for predicting AHR in the overall study population were 77.0% (95% CI = 66.8-85.4%), 63.9% (95% CI = 58.6-69.0), 35.3%, and 91.6%, respectively. When we restricted the study group to subjects with normal lung function, the results were similar.

Conclusion

Our results indicate that FEF_25-75 %pred can be used as a surrogate for predicting AHR in patients with respiratory symptoms.

Ultra-high-resolution computed tomography shows changes in the lungs related with airway hyperresponsiveness in a murine asthma model

In vivo presentation of airway hyper-responsiveness (AHR) at the different time points of the allergic reaction is not clearly understood. The purpose of this study was to investigate how AHR manifests in the airway and the lung parenchyma in vivo following exposure to different stimuli and in the early and late phases of asthma after allergen exposure. Ovalbumin (OVA)-induced allergic asthma model was established using 6-week female BALB/c mice. Enhanced pause was measured with a non-invasive method to assess AHR. The dynamic changes of the airway and lung parenchyma were evaluated with ultra-high-resolution computed tomography (128 multi-detector, 1024 × 1024 matrix) for 10 h. While the methacholine challenge showed no grossly visible changes in the proximal airway and lung parenchyma despite provoking AHR, the OVA challenge induced significant immediate changes manifesting as peribronchial ground glass opacities, consolidations, air-trapping, and paradoxical proximal airway dilatations. After resolution of immediate response, multiple episodes of AHRs occurred with paradoxical proximal airway dilatation and peripheral air-trapping in late phase over a prolonged time period in vivo. Understanding of airflow limitation based on the structural changes of asthmatic airway would be helpful to make an appropriate drug delivery strategy for the treatment of asthma.

Exercise-induced alterations in phospholipid hydrolysis, airway surfactant, and eicosanoids and their role in airway hyperresponsiveness in asthma

The mechanisms responsible for driving endogenous airway hyperresponsiveness (AHR) in the form of exercise-induced bronchoconstriction (EIB) are not fully understood. We examined alterations in airway phospholipid hydrolysis, surfactant degradation, and lipid mediator release in relation to AHR severity and changes induced by exercise challenge. Paired induced sputum (n = 18) and bronchoalveolar lavage (BAL) fluid (n = 11) were obtained before and after exercise challenge in asthmatic subjects. Samples were analyzed for phospholipid structure, surfactant function, and levels of eicosanoids and secreted phospholipase A₂ group 10 (sPLA₂-X). A primary epithelial cell culture model was used to model effects of osmotic stress on sPLA₂-X. Exercise challenge resulted in increased surfactant degradation, phospholipase activity, and eicosanoid production in sputum samples of all patients. Subjects with EIB had higher levels of surfactant degradation and phospholipase activity in BAL fluid. Higher basal sputum levels of cysteinyl leukotrienes (CysLTs) and prostaglandin D₂ (PGD₂) were associated with direct AHR, and both the postexercise and absolute change in CysLTs and PGD₂ levels were associated with EIB severity. Surfactant function either was abnormal at baseline or became abnormal after exercise challenge. Baseline levels of sPLA₂-X in sputum and the absolute change in amount of sPLA₂-X with exercise were positively correlated with EIB severity. Osmotic stress ex vivo resulted in movement of water and release of sPLA₂-X to the apical surface. In summary, exercise challenge promotes changes in phospholipid structure and eicosanoid release in asthma, providing two mechanisms that promote bronchoconstriction, particularly in individuals with EIB who have higher basal levels of phospholipid turnover.

Does Bilevel Noninvasive Ventilation Have a Bronchodilating Effect and Alter Respiratory Mechanics in Asthmatic Individuals After Bronchoprovocation? Randomized, Crossover Study

Background: Noninvasive ventilation (NIV) has an additional important effect that does not occur with medicinal therapy: a reduction in the work of breathing. Understanding the mechanical effects of these therapies is of considerable importance and can affect clinical decision making. Objective: Evaluate the effects of NIV compared to albuterol on lung function and respiratory mechanics in asthmatic adolescents and young adults after bronchoprovocation and determine the effects of a hypertonic saline solution on lung function respiratory mechanics. Methods: A randomized crossover study was conducted involving individuals with a diagnosis of asthma. Evaluations were performed with optoelectronic plethysmography (OEP) and spirometry at baseline, after the bronchial provocation test with 4.5% saline solution and after the intervention. The order of the procedures (bilevel NIV and albuterol) was randomized, with the participants crossing over to the other treatment after a 1-week washout period. Inspiratory positive airway pressure (IPAP) 12 and expiratory positive airway pressure (EPAP) 8 cmH₂O were set for 10 minutes and the dose of albuterol was 400 μg. Results: Forty individuals were included in the study (mean age: 21.6 ± 4 years; 24 females). The recovery of FEV₁% was 87.9% (80.8 ± 35 to 101.1 ± 46.1, p < 0.05) after NIV and 95.9% (84.4 ± 42.4 to 110.3 ± 44.3, p < 0.05) after albuterol. Inspiratory capacity (IC; L) reduced 12% to 15% after bronchoprovocation, with 100% recovery using NIV (2.1 ± 0.7 to 2.42.4 ± 0.6, p < 0.05) and 107.6% using albuterol (2.2 ± 0.8 to 2.8 ± 1.1, p < 0.05). Regarding OEP variables, tidal volume had greater participation in the thoracic compartment. NIV led to an increase in minute volume and a return to the baseline value, which did not occur with albuterol. Conclusion: NIV recovered FEV₁ and improves signs of hyperinflation by improving IC. Bronchoprovocation with a hypertonic solution reduced FEV₁ by 20% and reduced IC. NIV led to a faster recovery of minute volume and reduced the contraction velocity of the muscles of the rib cage compared to albuterol, although the effects on lung function were less intense.

Cardiopulmonary exercise testing in patients with asthma: What is its clinical value?

Asthma is one of the most common respiratory disorders, characterized by fully or largely reversible airflow limitation. Asthma symptoms can be triggered or magnified during exertion, while physical activity limitation is often present among asthmatic patients. Cardiopulmonary exercise testing (CPET) is a dynamic, non-invasive technique which provides a thorough assessment of exercise physiology, involving the integrative assessment of cardiopulmonary, neuromuscular and metabolic responses during exercise. This review summarizes current evidence regarding the utility of CPET in the diagnostic work-up, functional evaluation and therapeutic intervention among patients with asthma, highlighting its potential role for thorough patient assessment and physician clinical desicion-making.

Assessing paediatric exercise-induced bronchoconstriction using electromyography

BACKGROUND

Asthma is one of the most common chronic diseases in childhood, occurring in up to 10% of all children. Exercise-induced bronchoconstriction (EIB) is indicative of uncontrolled asthma and can be assessed using an exercise challenge test (ECT). However, this test requires children to undergo demanding repetitive forced breathing manoeuvres. We aimed to study the electrical activity of the diaphragm using surface electromyography (EMG) as an alternative measure to assess EIB.

METHODS

Forty-two children suspected of EIB performed an ECT wearing a portable EMG amplifier. EIB was defined as a fall in FEV 1 of more than 13%. Children performed spirometry before exercise, and at 1, 3 and 6 min after exercise until the nadir FEV1 was attained and after the use of a bronchodilator. EMG measurements were obtained between spirometry measurements.

RESULTS

Twenty out of 42 children were diagnosed with EIB. EMG peak amplitudes measured at the diaphragm increased significantly more in children with EIB; 4.85 μV (1.82-7.84), compared to children without EIB; 0.20 μV (-0.10-0.54), (p<0.001) at the lowest FEV 1 post-exercise. Furthermore, the increase in EMG peak amplitude could accurately distinguish between EIB and non-EIB using a cut-off of 1.15 μV (sensitivity 95%, specificity 91%).

CONCLUSION

EMG measurements of the diaphragm are strongly related to the FEV1 and can accurately identify EIB. EMG measurements are a less invasive, effort-independent measure to assess EIB and could be an alternative when spirometry is not feasible.

Diagnostic value of bronchoprovocation challenge with adenosine monophosphate versus exercise testing in early diagnosis of asthma

Background

Airway hyperresponsiveness (AHR) is a characteristic feature of bronchial asthma and is diagnosed using direct and indirect bronchoprovocation tests. The diagnosis of AHR is a challenge in symptomatic patients with a normal baseline prebronchodilator spirometry and postbronchodilator spirometry. Exercise-induced asthma or exercise-induced bronchoconstriction (EIB) is a distinct form of AHR. There is no single test that is sufficient to exclude AHR in symptomatic military personnel with normal spirometry. This study was conducted to compare the diagnostic value of indirect bronchoprovocation test using inhaled adenosine monophosphate (AMP) and exercise challenge test (ECT) in the diagnosis of EIB.

Methods

A crossover study was conducted with consecutive sampling of patients presenting with symptoms suggestive of asthma and with normal spirometry results who were subjected to both ECT and bronchoprovocation test using inhaled AMP on separate days.

Results

Forty participants were recruited (the mean age: 25 yrs, 100% male). The commonest presentation was breathlessness on exercise (55%). With exercise alone, 40% tested positive for AHR, while with AMP alone, the positivity increased to 53%, and the difference was statistically significant (p= 0.03). Exercise alone failed to detect 8 cases that tested positive for AHR by inhaled AMP challenge.

Conclusion

Indirect bronchoprovocation test using inhaled AMP may be used to diagnose AHR in conditions in which exercise challenge testing is not available or the patient is unable to complete ECT.

Diagnostic comparison of methacholine and mannitol bronchial challenge tests for identifying bronchial hyperresponsiveness in asthma: a systematic review and meta-analysis

OBJECTIVE

Bronchial hyperresponsiveness (BHR) is a representative feature of asthma. Although methacholine and mannitol are commonly used for bronchial challenge tests, the optimal roles of the two agents for assessing BHR remain unclear. We compared the diagnostic performance of methacholine and mannitol in bronchial challenge tests.

METHODS

A systematic literature search was performed using MEDLINE, EMBASE, and the Cochrane Central Register. The sensitivity, specificity, diagnostic odds ratio (DOR), and a hierarchical summary of the receiver-operating characteristic curve (HSROC) of the two agents for detecting BHR in asthma were pooled using meta-analysis. A meta-regression analysis was used to identify potential sources of heterogeneity within the selected studies.

RESULTS

We identified six studies comprising 565 patients. The pooled sensitivity, specificity, and DOR of methacholine were 0.61 (95%CI, 0.44-0.76), 0.93 (95%CI, 0.70-0.99), and 23.47 (95% CI, 2.51-219.89), respectively. The pooled sensitivity, specificity, and diagnostic odds ratio of mannitol were 0.50 (95%CI, 0.28-0.73), 0.97 (95% CI, 0.94-0.99), and 35.22 (95% CI, 8.82-140.62), respectively. The area under the HSROC for mannitol was higher than that for methacholine (0.97 vs. 0.81, p < 0.01). Considerable between-study heterogeneity was present for sensitivity and specificity in studies of both index tests. Univariate meta-regression analysis revealed that age and sex of the study participants were probable sources of heterogeneity for specificity in studies of methacholine.

CONCLUSION

Although mannitol showed better diagnostic performance than methacholine for identifying BHR in asthma, substantial between-study heterogeneity necessitates caution when interpreting the data.

The impact of reflexology and homeopathy added to conventional asthma treatment on markers of airway inflammation - a randomised study

Background

Asthma is a common chronic airway disease associated with hyperresponsiveness and airway inflammation. Anti-inflammatory medication especially inhaled corticosteroids are important for control of airway inflammation, decrease of airway hyperresponsiveness and lung function variability, reduce asthma symptoms, and improve lung function as well as quality of life. Most studies investigating the influence of complementary and alternative medicine (CAM) in asthma measure clinical effectiveness, but only few evaluate the impact on markers of airway inflammation.

Objective

The aim of this study was to investigate the effect of reflexology and homeopathy added to conventional treatment on different markers of airway inflammation in asthma.

Methods

Eighty-four patients with asthma were randomized to receive conventional treatment alone or conventional treatment with addition of homeopathy or reflexology in a single center, investigator blinded, controlled, one-year trial. During the study period, patients regularly consulted their general practitioner for evaluation and asthma treatment. At randomization, and after 6 and 12 months, methacholine challenge test and measurement of exhaled nitric oxide were performed. Blood samples were collected for eosinophil count and measurement of serum eosinophil cationic protein.

Results

No significant differences between groups for any of the inflammatory markers were demonstrated. Methacholine responsiveness improved in all three groups but improvements were not statistically significant within and between groups.

Conclusions

This randomized controlled study of reflexology and homeopathy failed to show significant improvement on selected markers of inflammation and airway hyperresponsiveness in asthma.

Exercise-induced bronchoconstriction in elite or endurance athletes:: Pathogenesis and diagnostic considerations

OBJECTIVE

To review the pathogenesis and evaluation of exercise-induced bronchoconstriction pertaining to the elite or endurance athlete, as well as propose a diagnostic algorithm based on the current literature.

DATA SOURCES

Studies were identified using Ovid MEDLINE and reference lists of key articles.

STUDY SELECTIONS

Randomized controlled trials were selected when available. Systematic reviews and meta-analyses of peer-reviewed literature were included, as were retrospective studies and observational studies of clinical interest.

RESULTS

Exercise-induced bronchoconstriction (EIB) is the physiologic entity in which exercise induces acute narrowing of the airways and occurs in patients both with and without asthma. It may present with or without respiratory symptoms, and the underlying cause is likely attributable to environment stressors to the airway encountered during exercise. These include the osmotic effects of inhaled dry air, temperature variations, autonomic nervous system dysregulation, sensory nerve reactivity, and airway epithelial injury. Deposition of allergens, particulate matter, and gaseous pollutants into the airway also contribute. Elite and endurance athletes are exposed to these stressors more frequently and in greater duration than the general population.

CONCLUSION

A greater awareness of EIB among elite and endurance athletes is needed, and a thorough evaluation should be performed if EIB is suspected in this population. We propose an algorithm to aid in this evaluation. Symptoms should not be solely relied on for diagnosis but should be taken into the context of bronchoprovocative challenges, which should replicate the competitive environment as closely as possible. Further research is needed to validate these tests' predictive values.

Airway epithelium-shifted mast cell infiltration regulates asthmatic inflammation via IL-33 signaling

Asthma is a heterogeneous syndrome that has been subdivided into physiologic phenotypes and molecular endotypes. The most specific phenotypic manifestation of asthma is indirect airway hyperresponsiveness (AHR), and a prominent molecular endotype is the presence of type 2 inflammation. The underlying basis for type 2 inflammation and its relationship to AHR are incompletely understood. We assessed the expression of type 2 cytokines in the airways of subjects with and without asthma who were extensively characterized for AHR. Using quantitative morphometry of the airway wall, we identified a shift in mast cells from the submucosa to the airway epithelium specifically associated with both type 2 inflammation and indirect AHR. Using ex vivo modeling of primary airway epithelial cells in organotypic coculture with mast cells, we show that epithelial-derived IL-33 uniquely induced type 2 cytokines in mast cells, which regulated the expression of epithelial IL33 in a feed-forward loop. This feed-forward loop was accentuated in epithelial cells derived from subjects with asthma. These results demonstrate that type 2 inflammation and indirect AHR in asthma are related to a shift in mast cell infiltration to the airway epithelium, and that mast cells cooperate with epithelial cells through IL-33 signaling to regulate type 2 inflammation.

Factors Associated with Positive Adenosine Challenge Test in Young Children with Suspected Asthma

Background: To investigate the predictive factors associated with positive adenosine monophosphate challenge using the auscultation method (AMP-PCW) test results. Methods: This is a prospective study of young children with suspected asthma who underwent AMP-PCW test. Patients with a positive AMP-PCW test were compared with those with a negative AMP-PCW. A multivariate logistic regression model was performed to identify the independent determinants of positive AMP-PCW. Results: A total of 159 patients completed the AMP-PCW test. The median age was 53 months. In total, 54.0% of patients had a positive AMP-PCW. The prevalence of atopic dermatitis and family history of asthma and allergy were significantly higher among the positive AMP-PCW group (P = 0.04, P = 0.02, and P = 0.007, respectively), as were the prevalences of elevated immunoglobulin E (IgE), peripheral blood eosinophils percentage (P = 0.003, P < 0.001, respectively), and number of emergency department (ED) visits/hospitalizations before AMP-PCW test (P = 0.006). A significant inverse correlation exists between peripheral blood eosinophils percentage and serum IgE levels with the AMP end-point concentrations (r = -0.302, P = 0.001, and r = -0.312, P = 0.001, respectively). In multivariate logistic regression model, peripheral blood eosinophils percentage, IgE levels, and the number of ED visits/hospitalizations before the AMP-PCW test were found as independent predictors for positive AMP-PCW test result. Conclusions: Our results suggest that bronchial responsiveness to AMP-PCW is related to proxy markers of airway inflammation (elevated eosinophils and IgE levels) and clinical exacerbation of asthma before the test. This may support the role of AMP-PCW in detecting inflammatory changes and monitoring their trend among young children with suspected asthma.

The Visual Analog Scale detects exercise-induced bronchoconstriction in children with asthma

Objective: Exercise-induced bronchoconstriction (EIB) is a specific morbidity of childhood asthma and an important sign of uncontrolled asthma. The occurrence of EIB is insufficiently identified by the Childhood Asthma Control Test (C-ACT) and Asthma Control Test (ACT). This study aimed to (1) evaluate the Visual Analog Scale (VAS) for dyspnea as a tool to detect EIB in asthmatic children and (2) assess the value of combining (C-)ACT outcomes with VAS scores. Methods: We measured EIB in 75 asthmatic children (mean age 10.8 years) with a standardized exercise challenge test (ECT) performed in cold and dry air. Children and parents reported VAS dyspnea scores before and after the ECT. Asthma control was assessed by the (C-)ACT. Results: Changes in VAS scores (ΔVAS) of children and parents correlated moderately with fall in forced expiratory volume in 1 second (FEV₁), respectively r_s=0.57 (p < .001) and r_s=0.58 (p < .001). At a ΔVAS cutoff value of ≥3 in children, sensitivity and specificity for EIB were 80% and 79% (AUC 0.82). Out of 38 children diagnosed with EIB, 37 had a (C-)ACT score of ≤19 and/or a ΔVAS of ≥3, corresponding with a sensitivity of 97% and a negative predictive value of 96%. Conclusion: This study shows that the VAS could be an effective additional tool for diagnosing EIB in children. A reported difference in VAS scores of ≥3 after a standardized ECT combined with low (C-)ACT scores was highly effective in detecting and excluding EIB.

Laser-capture microdissection of murine lung for differential cellular RNA analysis

The lung tissue contains a heterogeneous milieu of bronchioles, epithelial, airway smooth muscle (ASM), alveolar, and immune cell types. Healthy bronchiole comprises epithelial cells surrounded by ASM cells and helps in normal respiration. In contrast, airway remodeling, or plasticity, increases surrounding of bronchial epithelium during inflammation, especially in asthmatic condition. Given the profound functional difference between ASM, epithelial, and other cell types in the lung, it is imperative to separate and isolate different cell types of lungs for genomics, proteomics, and molecular analysis, which will improve the diagnostic and therapeutic approach to treat cell-specific lung disorders. Laser capture microdissection (LCM) is the technique generally used for the isolation of specific cell populations under direct visual inspection, which plays a crucial role to evaluate cell-specific effect in clinical and preclinical setup. However, maintenance of tissue RNA quality and integrity in LCM studies are very challenging tasks. It is obvious to believe that the major factor affecting the RNA quality is tissue-fixation method. The prime focus of this study was to address the RNA quality factors within the lung tissue using the different solvent system to fix tissue sample to obtain high-quality RNA. Paraformaldehyde and Carnoy's solutions were used for fixing the lung tissue and compared RNA integrity in LCM captured lung tissue samples. To further confirm the quality of RNA, we measured cellular marker genes in collected lung tissue samples from control and mixed allergen (MA)-induced asthmatic mouse model using qRT-PCR technique. RNA integrity number showed a significantly better quality of RNA in lung tissue samples fixed with Carnoy's solution compared to paraformaldehyde solution. Isolated RNA from MA-induced asthmatic murine lung epithelium, smooth muscle, and granulomatous foci using LCM showed a significant increase in remodeling gene expression compared to control which confirm the quality and integrity of isolated RNA. Overall, the study concludes tissue fixation solvent can alter the quality of RNA in the lung and the outcome of the results.

Bronchoprovocation Testing in Asthma: An Update

Bronchial hyperresponsiveness (BHR) is defined as a heightened bronchoconstrictive response to airway stimuli. It complements the cardinal features in asthma, such as variable or reversible airflow limitation and airway inflammation. Although BHR is considered a pathophysiologic hallmark of asthma, it should be acknowledged that this property of the airway is dynamic, because its severity and even presence can vary over time with disease activity, triggers or specific exposure, and with treatment. In addition, it is important to recognize that there is a component that is not reflective of a specific disease entity.

A sputum 6-gene signature predicts future exacerbations of poorly controlled asthma

BACKGROUND

Improved diagnostic tools for predicting future exacerbation frequency in asthmatic patients are required. A sputum gene expression signature of 6 biomarkers (6-gene signature [6GS], including Charcot-Leyden crystal galectin [CLC]; carboxypeptidase 3 [CPA3]; deoxyribonuclease 1-like 3 [DNASE1L3]; alkaline phosphatase, liver/bone/kidney [ALPL]; CXCR2; and IL1B) predicts inflammatory and treatment response phenotypes in patients with stable asthma. Recently, we demonstrated that azithromycin (AZM) add-on treatment in patients with uncontrolled moderate-to-severe asthma significantly reduced asthma exacerbations (AMAZES clinical trial).

OBJECTIVES

We sought to test whether the 6GS predicts future exacerbation and inflammatory phenotypes in a subpopulation of AMAZES and to test the effect of AZM therapy on 6GS expression and prognostic capacity.

METHODS

One hundred forty-two patients (73 placebo-treated and 69 AZM-treated patients) had sputum stored for quantitative PCR of 6GS markers at baseline and after 48 weeks of treatment. Logistic regression and receiver operating characteristic and area under the curve (AUC) determination were performed on baseline measures, and in an exploratory analysis the predictive value of the 6GS was compared with conventional biomarkers for exacerbation and inflammatory phenotypes.

RESULTS

The 6GS significantly predicted all future exacerbation phenotypes tested. Calculated AUCs for the 6GS were significantly greater than AUCs for peripheral blood eosinophil counts, sputum neutrophil counts, and combined sputum eosinophil and neutrophil counts. 6GS AUCs were also numerically but not significantly greater than those for fractional exhaled nitric oxide values and sputum eosinophil counts. AZM treatment altered neither 6GS expression nor the predictive capacity of the 6GS for future exacerbation phenotypes. The 6GS was a significant predictor of airway inflammatory phenotype in this population.

CONCLUSION

We demonstrate that a sputum gene signature can predict future exacerbation phenotypes of asthma, with the greatest biomarker performance in identifying those who would experience frequent severe exacerbations. AZM therapy did not modify 6GS expression or biomarker performance, suggesting the therapeutic action of AZM is independent of 6GS-related inflammatory pathways.

ERS technical standard on bronchial challenge testing: pathophysiology and methodology of indirect airway challenge testing

Recently, this international task force reported the general considerations for bronchial challenge testing and the performance of the methacholine challenge test, a "direct" airway challenge test. Here, the task force provides an updated description of the pathophysiology and the methods to conduct indirect challenge tests. Because indirect challenge tests trigger airway narrowing through the activation of endogenous pathways that are involved in asthma, indirect challenge tests tend to be specific for asthma and reveal much about the biology of asthma, but may be less sensitive than direct tests for the detection of airway hyperresponsiveness. We provide recommendations for the conduct and interpretation of hyperpnoea challenge tests such as dry air exercise challenge and eucapnic voluntary hyperpnoea that provide a single strong stimulus for airway narrowing. This technical standard expands the recommendations to additional indirect tests such as hypertonic saline, mannitol and adenosine challenge that are incremental tests, but still retain characteristics of other indirect challenges. Assessment of airway hyperresponsiveness, with direct and indirect tests, are valuable tools to understand and to monitor airway function and to characterise the underlying asthma phenotype to guide therapy. The tests should be interpreted within the context of the clinical features of asthma.

Exhaled nitric oxide and mannitol test to predict exercise-induced bronchoconstriction

BACKGROUND

Exercise-induced bronchoconstriction (EIB) is diagnosed via exercise challenge on a treadmill, but such testing requires complex equipment and sufficient health-care resources. The fraction of exhaled nitric oxide (FeNO) test and mannitol bronchial provocation test (BPT) may serve as a surrogate for exercise testing.

METHODS

We compared the diagnostic utilities of the FeNO test and mannitol BPT in predicting EIB in asthmatic children. We retrospectively analyzed data from 60 asthmatic children aged 6-16 years. We compared the exercise BPT results, FeNO levels, and mannitol BPT data.

RESULTS

All subjects were divided into exercise-positive (n = 41) or -negative (n = 19) BPT groups. Of the 41 exercise-positive patients, 32 were mannitol BPT positive and nine were mannitol BPT negative. Of the 19 exercise-negative patients, nine and 10, respectively, were mannitol BPT positive and BPT negative. The maximum % forced expiratory volume in 1 s (FEV₁ ) decrease after exercise was positively correlated with FeNO (r = 0.556, P < 0.001), and with mannitol response-dose ratio (RDR; r = 0.416, P = 0.001). The receiver operating characteristic (ROC) curve for FeNO to discriminate between asthmatic subjects with and without EIB had an area under the curve (AUC) of 0.771 (95%CI: 0.643-0.870). The discriminatory ROC curve for mannitol RDR had an AUC of 0.763 (95%CI: 0.633-0.864). The AUC of FeNO and mannitol RDR did not differ significantly.

CONCLUSIONS

EIB significantly correlated with both FeNO and mannitol BPT data. Given that both methods similarly predicted EIB in asthmatic children, the simpler and safer FeNO test alone may be a clinically useful diagnostic tool.

The efficacy and safety of mannitol challenge in a workplace setting for assessing asthma prevalence

OBJECTIVE

There is no standard definition of asthma for epidemiological purposes; most surveys use symptoms and bronchial hyperresponsiveness. Few studies tested mannitol challenge test (MCT) in occupational settings. We sought to determine efficacy and safety of MCT in detecting subjects with asthma symptoms in the workplace.

METHODS

In this cross-sectional study we recruited 908 workers in 2 universities; they underwent a respiratory questionnaire, spirometry, skin prick tests, and MCT.

RESULTS

Eight hundred and eleven subjects completed the study; 11.1% had a positive MCT; 8.14% had asthma. MCT had low sensitivity (35.4-61.9%) but high specificity (90.2-94.9%) to detect symptomatic individuals. The most prevalent symptom was wheezing in the last 12 months. Twenty-four of those with a positive MCT (26.7%) had no positive replies to the questions on asthma symptoms. Among subjects with a positive MCT, 71.9% achieved 95% of baseline FEV₁ after 15 minutes of salbutamol recovery treatment. Nine subjects (1.1%) had adverse events that prevented the test from being completed.

CONCLUSIONS

MCT has high specificity but low sensitivity to detect symptomatic subjects in the workplace. It may detect subjects with hyperresponsiveness but no symptoms, who could be at risk of developing airway diseases. The test is safe and well tolerated.

Nonspecific Bronchoprovocation Test

Bronchial asthma is a disease characterized by the condition of airway hyper-responsiveness, which serves to produce narrowing of the airway secondary to airway inflammation and/or various spasm-inducing stimulus. Nonspecific bronchoprovocation testing is an important method implemented for the purpose of diagnosing asthma; this test measures the actual degree of airway hyper-responsiveness and utilizes direct and indirect bronchoprovocation testing. Direct bronchoprovocation testing using methacholine or histamine may have superior sensitivity as these substances directly stimulate the airway smooth muscle cells. On the other hand, this method also engenders the specific disadvantage of relatively low specificity. Indirect bronchoprovocation testing using mannitol, exercise, hypertonic saline, adenosine and hyperventilation serves to produce reactions in the airway smooth muscle cells by liberating mediators with stimulation of airway inflammatory cells. Therefore, this method has the advantage of high specificity and also demonstrates relatively low sensitivity. Direct and indirect testing both call for very precise descriptions of very specific measurement conditions. In addition, it has become evident that challenge testing utilizing each of the various bronchoconstrictor stimuli requires distinct and specific protocols. It is therefore important that the clinician understand the mechanism by which the most commonly used bronchoprovocation testing works. It is important that the clinician understand the mechanism of action in the testing, whether direct stimuli (methacholine) or indirect stimuli (mannitol, exercise) is implemented, when the testing is performed and the results interpreted.

Hypertonic saline inhibits airway smooth muscle contraction by inhibiting Ca2+ sensitization

The effects of hypertonic solution on airway smooth muscle (ASM) contraction and the underlying mechanisms are largely unknown. We found that hypertonic saline (HS) inhibited acetylcholine (ACh)-induced contraction of ASM from the mouse trachea and human bronchi. In single mouse ASM cells (ASMCs), ACh induced an increase in intracellular Ca²⁺ that was further enhanced by 5% NaCl, indicating that the HS-induced inhibition of ASM contraction was not mediated by a decrease in cytosolic Ca²⁺ . The Rho-associated kinase (ROCK) inhibitor Y-27632 relaxed ACh-induced precontraction of mouse tracheal rings. However, such inhibition was not observed after the relaxation induced by 5% NaCl. Moreover, the incubation of mouse tracheal rings with 5% NaCl decreased ACh-induced phosphorylation of myosin light chain 20 and myosin phosphatase target subunit 1. These data indicate that HS inhibits the contraction of ASM by inhibiting Ca²⁺ sensitization, not by decreasing intracellular Ca²⁺ .

Cellular Na+ handling mechanisms involved in airway smooth muscle contraction (Review)

A decrease in bronchial diameter is designated as bronchoconstriction (BC) and impedes the flow of air through the airway. Asthma is characterized by inflammation of the airways, reversible BC and nonspecific hyperreactivity. These last two symptoms are dependent on airway smooth muscle. Stimuli that trigger contraction can be characterized as chemical (neurotransmitters, cytokines and terpenoids) and physical (volume inspired, air pressure). Both stimuli activate signaling pathways by acting on membrane proteins and facilitating the passage of ions through the membrane, generating a voltage change and a subsequent depolarization. Na⁺ plays an important role in preserving the resting membrane potential; this ion is extracted from the cells by the Na⁺/K⁺ ATPase (NKA) or introduced into the cytoplasm by the Na⁺/Ca²⁺ exchanger (NCX). During depolarization, Na⁺ appears to accumulate in specific regions beneath the plasma membrane, generating local concentration gradients which determine the handling of Ca²⁺. At rest, the smooth muscle has a basal tone that is preserved by the continuous adjustment of intracytoplasmic concentrations of Ca²⁺ and Na⁺. At homeostasis, the Na⁺ concentration is primarily dependent on three structures: the NKA, the NCX and non-specific cation channels (NSCC). These three structures, their functions and the available evidence of the probable role of Na⁺ in asthma are described in the present review.

Airway hyperresponsiveness to mannitol and methacholine and exhaled nitric oxide in children with asthma

OBJECTIVE

Asthma is characterized by airway hyperresponsiveness (AHR), inflammation, and obstruction. AHR to stimuli that indirectly cause bronchial smooth muscle (BSM) contractions via release of endogenous mediators is thought to better reflect airway inflammation than AHR to stimuli that act directly on BSM. Fractional exhaled nitric oxide (FeNO) is a useful parameter for noninvasive clinical airway inflammation assessments. Accordingly, this study aimed to examine the relationships of mannitol and methacholine challenge test outcomes with FeNO and the influence of inhaled corticosteroid treatment in children with asthma.

METHODS

One hundred thirty-four asthmatic children (89 males; ages: 5-17 years, median: 9 years) underwent spirometry, FeNO measurement, serum total/specific IgE testing, and blood eosinophil count. All subjects were challenged with mannitol dry powder (MDP; AridolH, Pharmaxis, Australia) and methacholine at 7-day intervals. Data of steroid-treated and steroid-naïve children were compared.

RESULTS

Positive responses to MDP and methacholine challenge tests were observed in 74.6% and 67.2% of total subject group, respectively, and 72 children had positive response to both challenge tests. The median FeNO level, response-dose ratio (RDR) of PC₂₀ methacholine, and RDR of PD₁₅ MDP were significantly higher in the steroid-treated group than in the steroid-naïve group (p < 0.001, 0.226, and 0.004, respectively). FeNO levels associated significantly with PD₁₅ MDP and RDR PD₁₅ MDP in total subject populations (p = 0.016 and 0.003, respectively); however, a significant correlation between FeNO and RDR PD₁₅ MDP was observed only in the steroid-naïve group.

CONCLUSIONS

Compared with AHR to methacholine, AHR to MDP more closely reflected the level of FeNO in steroid-naïve asthmatic children.

Risk and safety requirements for diagnostic and therapeutic procedures in allergology: World Allergy Organization Statement

One of the major concerns in the practice of allergy is related to the safety of procedures for the diagnosis and treatment of allergic disease. Management (diagnosis and treatment) of hypersensitivity disorders involves often intentional exposure to potentially allergenic substances (during skin testing), deliberate induction in the office of allergic symptoms to offending compounds (provocation tests) or intentional application of potentially dangerous substances (allergy vaccine) to sensitized patients. These situations may be associated with a significant risk of unwanted, excessive or even dangerous reactions, which in many instances cannot be completely avoided. However, adverse reactions can be minimized or even avoided if a physician is fully aware of potential risk and is prepared to appropriately handle the situation. Information on the risk of diagnostic and therapeutic procedures in allergic diseases has been accumulated in the medical literature for decades; however, except for allergen specific immunotherapy, it has never been presented in a systematic fashion. Up to now no single document addressed the risk of the most commonly used medical procedures in the allergy office nor attempted to present general requirements necessary to assure the safety of these procedures. Following review of available literature a group of allergy experts within the World Allergy Organization (WAO), representing various continents and areas of allergy expertise, presents this report on risk associated with diagnostic and therapeutic procedures in allergology and proposes a consensus on safety requirements for performing procedures in allergy offices. Optimal safety measures including appropriate location, type and required time of supervision, availability of safety equipment, access to specialized emergency services, etc. for various procedures have been recommended. This document should be useful for allergists with already established practices and experience as well as to other specialists taking care of patients with allergies.

Comparison of diagnostic validity of mannitol and methacholine challenges and relationship to clinical status and airway inflammation in steroid-naïve asthmatic patients

OBJECTIVES

The purpose of this study was to demonstrate and compare the diagnostic validity of two bronchial challenges and to investigate their correlation with patient clinical status, atopy and inflammation markers.

METHODS

Eighty-eight patients, 47 women and 41 men, mean age 38.56 ± 16.73 years who presented with asthma related symptoms and were not on any anti-asthma medication, were challenged with mannitol and methacholine on separate days. Medical history regarding asthmatic symptoms, physical examination, skin prick tests and FeNO levels were also assessed. The clinical diagnosis of asthma was based on bronchodilator reversibility test.

RESULTS

Sixty-seven patients were diagnosed with asthma and 21 without asthma. Both methacholine (P < 0.014) and mannitol (P < 0.000) challenges were significant in diagnosing asthma. The positive/negative predictive value was 93.33%/41.86% for methacholine, 97.72%/45.45% for mannitol and 97.05%/45.45%. for both methods assessed together. Worthy of note that 22% of asthmatics had both tests negative. There was a negative correlation between PC20 of methacholine and the FeNO level P < 0.001, and positive with the PD15 of mannitol P < 0.001 and the pre-test FEV₁% pred P < 0.005, whereas PD15 of mannitol was negatively correlated with the FeNO level P < 0.001. Furthermore, dyspnea was the only asthmatic symptom associated with FeNO level P < 0.035 and the positivity of mannitol P < 0.014 and methacholine P < 0.04.

CONCLUSIONS

Both challenge tests were equivalent in diagnosing asthma. Nevertheless, specificity appeared to be slightly higher in mannitol challenge.

Stability of FeNO and airway hyperresponsiveness to mannitol in untreated asthmatics

OBJECTIVE

Airway hyperresponsiveness and airway inflammation are important hallmarks of asthma and are useful in asthma diagnosing, monitoring and treatment. The aim of the study was to assess whether two commonly used clinical tests, the mannitol challenge and Fraction of exhaled NO (FeNO), were stable clinical indicators over time in stable untreated asthmatics.

METHODS

54 non-smoking, asthma patients not treated with steroids were enrolled in the study and assessed at baseline and a median of 6 months later. At baseline and follow-up, FeNO and airway hyperesponsiveness to mannitol were measured, and asthma control was assessed with the Asthma Control Questionnaire (ACQ).

RESULTS

A total of 41 subjects completed both visits. Mean (SD) FEV1% at baseline was 94.1% (17.7) and at re-examination 94.6% (19.7) (ns). The ACQ score was unchanged from baseline (Mean (SD): 0.90 (± 0.73)) to follow-up 0.90 (± 0.74) (ns), as was the FEV₁% (94.1% (±17.1%) vs 94.6% (19.7%)(ns) indicating that patients were clinically stable during follow-up. The response to mannitol was unchanged at follow-up (Geometric mean (CI) of Response Dose Ratio (RDR) to mannitol: 0.026(0.013-0.046) vs 0.026(0.012-0.050) (ns). There was a slight decrease in FeNO at follow-up (25.5 ppb (19.7-32.9) to 21.9 ppb (17.1-28.2) (p < 0.001).

CONCLUSIONS

In steroid-free non-smoking asthmatics with constant symptom scores and lung function, airway responsiveness to mannitol remained at the same level over a period of months, while a minor change in exhaled FeNO was reported. These results suggest that mannitol is a stable, reliable marker of clinical disease activity.

Physical Activity in School-Aged Children with Asthma in an Urban City of Taiwan

BACKGROUND

It has been reported that physical activity is limited in children with asthma. The aims of this study were to compare and quantify the physical activity levels between asthmatic children and their healthy peers. Factors associated with limitation of physical activity in asthmatic children were also investigated.

METHODS

A total of 120 asthmatic children and 262 age-matched healthy controls were enrolled in this study. Clinical phenotype including severity and lung function were obtained from medical records. A questionnaire addressing physical activity, asthma diagnosis, symptoms, parental health beliefs, physician's advice and, community resources was accomplished by children and their parents. The physical activity levels of children with and without asthma were compared. Factors that might limit the activity level were analyzed.

RESULTS

Children with asthma were less active than their peers. The significant difference was between normal controls and moderate-to-severe asthmatic children, but not children with mild asthma. Among children with asthma, physical activity was associated with the severity level but not parental health beliefs, physician's advice, or the convenience for physical activity. Children with moderate or severe persistent asthma were more likely to be inactive.

CONCLUSION

Children with asthma had a lower level of physical activity, particularly those with moderate-to-severe asthma. To achieve an appropriate level of physical activity, improvement of asthma management and control is considered important.

Stepping down from combination asthma therapy: The predictors of outcome

BACKGROUND

Stepping down from combination asthma therapy (inhaled corticosteroids (ICS) + long-acting β2 agonists (LABA)) is often avoided due to fear of exacerbations, which may lead to overmedication in well-controlled asthma. A better knowledge about the predictors of outcome might encourage clinicians to start stepping down more often than previously.

METHODS

In 55 subjects with well controlled asthma and combination therapy, LABAs were discontinued first, followed by ICS dose halving, and then cessation, in six weeks' intervals. The ability of Juniper's asthma control questionnaire (ACQ), ambulatory peak flow monitoring, spirometry, and hypertonic saline challenge to predict the outcomes of medication reductions were assessed.

RESULTS

The proportions of subjects experiencing an exacerbation at each step were: 4 out of 55 subjects (7%) after LABA cessation, 4 out of 25 subjects (16%) after ICS dose halving, and 21 out of 46 subjects (46%) after ICS cessation. All exacerbations could be managed on an outpatient basis. There were 126 step-downs altogether. ACQ score < 0.29 (likelihood ratio 2.30 (1.05-5.05)), ACQ without spirometry < 0.15 (2.17 (0.96-4.90)) and FEV1 > 96% of predicted (2.18 (1.03-4.61)) predicted a successful outcome after step-down. Cough responsiveness to saline, bronchoconstrictive responsiveness to saline, and peak flow variation were not associated with the outcome.

CONCLUSION

Combination therapy can often be reduced in controlled asthma but total cessation of ICSs must be carefully considered. Simple investigations, namely asthma control assessment by validated questionnaire and spirometry, help to predict the outcome of stepping down.

TRIAL REGISTRY

The study was registered in ClinicalTrials.gov database (https://clinicaltrials.gov, KUH5801124).

Does airway hyperresponsiveness monitoring lead to improved asthma control?

The current guidelines recommend an approach to asthma management based on asthma control, rather than asthma severity. Although several specific questionnaires have been developed and control criteria have been established based on clinical guidelines, the evaluation of asthma control is still not optimal. In general, these indicators provide adequate assessment of current control, but they are more limited when estimating future risk. There is much evidence demonstrating the persistence of airway inflammation and airway hyperresponsiveness (AHR) in patients with total control. Therefore, the objective of this review was to analyse the possible role of AHR monitoring as an instrument for assessing asthma control. We will evaluate its capacity as an indicator for future risk, both for estimating the possibility of clinical deterioration and loss of lung function or exacerbations. Furthermore, its relationship with inhaled corticosteroid treatment will be analysed, while emphasizing its capacity for predicting response and adjusting dosage, as well as information about the capability of AHR for monitoring treatment. Last of all, we will discuss the main limitations and emerging opportunities of AHR as an assessment instrument for asthma control.

'Indirect' challenges from science to clinical practice

Indirect challenges act to provoke bronchoconstriction by causing the release of endogenous mediators and are used to identify airway hyper-responsiveness. This paper reviews the historical development of challenges, with exercise, eucapnic voluntary hyperpnoea (EVH) of dry air, wet hypertonic saline, and with dry powder mannitol, that preceded their use in clinical practice. The first challenge developed for clinical use was exercise. Physicians were keen for a standardized test to identify exercise-induced asthma (EIA) and to assess the effect of drugs such as disodium cromoglycate. EVH with dry air became a surrogate for exercise to increase ventilation to very high levels. A simple test was developed with EVH and used to identify EIA in defence force recruits and later in elite athletes. The research findings with different conditions of inspired air led to the conclusion that loss of water by evaporation from the airway surface was the stimulus to EIA. The proposal that water loss caused a transient increase in osmolarity led to the development of the hypertonic saline challenge. The wet aerosol challenge with 4.5% saline, provided a known osmotic stimulus, to which most asthmatics were sensitive. To simplify the osmotic challenge, a dry powder of mannitol was specially prepared and encapsulated. The test pack with different doses and an inhaler provided a common operating procedure that could be used at the point of care. All these challenge tests have a high specificity to identify currently active asthma. All have been used to assess the benefit of treatment with inhaled corticosteroids. Over the 50 years, the methods for testing became safer, less complex, and less expensive and all used forced expiratory volume in 1 sec to measure the response. Thus, they became practical to use routinely and were recommended in guidelines for use in clinical practice.

Breathing-related changes of respiratory resistance in vocal cord dysfunction

Vocal cord dysfunction induced by exercise in children with uncontrolled asthma was identified by laryngoscopy. The paradoxical adduction of the vocal cords was also indicated by the breathing-related changes of the forced oscillation respiratory resistance showing prominent increase during inspiration and a large positive difference between inspiration and expiration. The breathing-related changes of respiratory resistance offer thus a useful first-line technique to diagnose vocal cord dysfunction.

Asthma Control Test and Bronchial Challenge with Exercise in Pediatric Asthma

BACKGROUND

Poor asthma control can lead to exercise-induced bronchoconstriction (EIB), but the relationship between subjective disease control and EIB is unclear. No studies have compared asthma control test (ACT) scores of children with those of their parents regarding EIB. We assessed whether ACT scores predict the occurrence of EIB in two age groups. We also evaluated ACT scores and objective measures as explanatory variables for airway response to exercise.

METHODS

Patients (71, aged <12 years; 93, aged ≥12 years) and their parents completed an ACT questionnaire separately. Current therapy, skin prick testing, and spirometry at baseline and after exercise were assessed. EIB was defined as a fall in forced expiratory volume in 1 s (FEV1) of at least 12% from baseline. Sensitivity and specificity for cut-off values of ACT scores predictive of EIB were plotted, and the area under curve (AUC) was described.

RESULTS

Atopy and current therapy were similarly frequent. EIB was observed in 23.9% of children aged <12 years and in 33.3% of children aged ≥12 years. EIB occurrence in subjects previously scored as having full control (25), partial control (20-24), and no control (<20) varied according to the age group and responders. Percentages of EIB cases increased as ACT scores decreased in children aged ≥12 years alone (child ACT scores, 25: 21.9%, 20-24: 31.1%, <20: 62.5%, p = 0.017). Plots for ACT scores as predictors of EIB yielded low non-significant AUC values in children aged <12 years; in contrast, moderate AUC values emerged in children aged ≥12 years (child: 0.67, p = 0.007; parent: 0.69, p = 0.002). Sensitivity of ACT scores below 20 as a predictor of EIB was low in older children (child: 32.3%, parent: 22.6%), whereas specificity was high (child: 90.3%, parent: 93.5%). Multiple regression analysis with percent fall in FEV1 as dependent variable included FEV1/FVC%, ACT child score, and gender in the prediction model (r = 0.42, p = 0.000).

CONCLUSION

ACT scores are a more effective means of excluding than confirming EIB in asthmatic patients aged ≥12 years; their predictive value decreases in younger patients. ACT scores together with lung function may help to predict airway response to exercise. New tools for pediatric asthma assessment may optimize this association.

Association of asthma and anxiety: A nationwide population-based study in Taiwan

BACKGROUND

Few studies have investigated the bidirectional relationship between asthma and anxiety; we sought to investigate asthma and anxiety in a large national sample.

METHODS

Cases were identified from Taiwan's National Health Insurance Research Database with a new primary diagnosis of asthma (ICD-9:493) aged more than 15 years between 2000 and 2007. Case status required the presence of any inpatient diagnosis of asthma and/or at least one year diagnosis of asthma in outpatient service. These 22,797 cases were compared to 22,797 sex-, age-, residence- and insurance premium-matched controls and both groups were followed until the end of 2008 for instances of anxiety, defined as ICD-9 codes 300.0, 300.01, 300.02, 300.2, 300.21, 300.23, 300.3. Competing risk adjusted Cox regression analyses were applied, adjusting for sex, age, residence, insurance premium, prednisone use, Charlson comorbidity index, cardiovascular disease, diabetes, depression disorder, and hospital admission days for any disorder. The effect of asthma on the risk of panic disorder and the effect of anxiety disorder on the risk of later asthma were also examined as competing risk adjusted Cox regression analyses

RESULTS

Of the 45,594 subjects, 2792 were ascertained as having anxiety during a mean (SD) follow-up period of 5.3 (2.5) years. Asthma, females, older age, rural residence, depression disorder, and prednisone use were independent risks on anxiety in the fully adjusted model. Anxiety, older age, rural residence, and prednisone use were independent risks on asthma in the fully adjusted model.

LIMITATIONS

The severity of asthma and anxiety disorder, the duration of prednisone treatment and adherence, stressful life events, smoking, family history and relationship were not evaluated.

CONCLUSIONS

Bidirectional relationship between asthma and anxiety disorder was confirmed in this population, in dependent of a number of potential confounding factors.

The TRPV1 receptor agonist capsaicin is an ineffective bronchoprovocant in an experimental model of feline asthma

OBJECTIVES

Airway hyper-responsiveness (AHR), a key feature of feline asthma, can be measured using bronchoprovocation testing. Limitations of both direct and indirect bronchoprovocants evaluated to date in experimental feline asthma have led to a search for a more specific indirect bronchoprovocant (ie, one which relies on existing inflammatory cells or activated neural pathways in diseased but not healthy airways). We hypothesized that capsaicin, a transient receptor potential cation channel subfamily V member 1 agonist, would lead to dose-responsive increases in airway resistance as measured by ventilator-acquired pulmonary mechanics in experimentally asthmatic cats.

METHODS

Five cats induced to have asthma using Bermuda grass allergen (BGA) were studied. Twenty-four hours after aerosol challenge of BGA, cats were anesthetized and underwent neuromuscular blockade for ventilator-acquired pulmonary mechanics. Cats were monitored with pulse oximetry for hemoglobin desaturation. Parameters recorded on a breath-by-breath basis on the ventilator included airway resistance (Raw) and compliance. Saline at baseline and 10-fold increasing concentrations of capsaicin (0.4-4000.0 µM) were aerosolized for 30 s and data collected for 4 mins between doses. The intended endpoint of the study was a doubling in baseline airway resistance, halving of compliance or oxygen desaturation <75%.

RESULTS

All cats completed the trial, reaching the highest dose of capsaicin without reaching any of the aforementioned endpoints. No biologically significant alteration in any other pulmonary mechanics parameter was noted.

CONCLUSIONS AND RELEVANCE

Capsaicin does not appear to be an effective bronchoprovocant in a feline asthma model.

Asthma risk factors

BACKGROUND

Bronchial asthma is one of the most common chronic diseases in childhood, with a current prevalence of 6% to 9%, but a prevalence that is increasing at an alarming rate. Asthma is a complex genetic disorder with strong environmental influence. It imposes a growing burden on our society in terms of morbidity, quality of life, and healthcare costs. Despite large-scale efforts, only a few asthma genes have been confirmed, suggesting that the genetic underpinning of asthma is highly complex.

METHODS

A review of the literature was performed regarding atopic and nonatopic asthma risk factors, including environmental risk factors and genetic studies in adults and children.

RESULTS

Several environmental risk factors have been identified to increase the risk of developing asthma such as exposure to air pollution and tobaccos smoke as well as occupational risk factors. In addition atopy, stress, and obesity all can increases the risk for asthma in genetically susceptible persons.

CONCLUSION

Asthma represents a dysfunctional interaction with our genes and the environment to which they are exposed, especially in fetal and early infant life. The increasing prevalence of asthma in all age groups indicate that our living environment and immunity are in imbalance with each other reacting with airway inflammation to the environmental exposures and often non-harmful proteins, such as allergens causing the current "asthma and allergy epidemic." Because of the close relationship between asthma and chronic rhinosinusitis, it is important that otolaryngologists have a good understanding of asthma, the etiologic factors associated with disease, and its evaluation and management.