Monitoring asthma therapy using indirect bronchial provocation tests

Asthma in elite athletes - do they have Type 2 or non-Type 2 disease? A new insight on the endotypes among elite athletes

Asthma and exercise-induced bronchoconstriction are highly prevalent in elite athletes compared with the general population. Some athletes have classic asthma with allergic sensitization; however, it seems that a proportion of athletes develop asthma as a result of several years of intensive training. It leads us to believe that asthma in athletes consists of at least two distinct endotypes - classic early-onset, Type 2 mediated asthma, and asthma with later onset caused by exercise which might be classified as non-Type 2 asthma. The purpose of this review is to evaluate the current literature on asthma in athletes focusing on inflammation and examine if asthma in athletes could be characterized as either Type 2- or non-Type 2 asthma.

Bronchial Provocation Testing for the Identification of Exercise-Induced Bronchoconstriction

Exercise-induced bronchoconstriction (EIB) occurs in patients with asthma, children, and otherwise healthy athletes. Poor diagnostic accuracy of respiratory symptoms during exercise requires objective assessment of EIB. The standardized tests currently available are based on the assumption that the provoking stimulus to EIB is dehydration of the airway surface fluid due to conditioning large volumes of inhaled air. "Indirect" bronchial provocation tests that use stimuli to cause endogenous release of bronchoconstricting mediators from airway inflammatory cells include dry air hyperpnea (eg, exercise and eucapnic voluntary hyperpnea) and osmotic aerosols (eg, inhaled mannitol). The airway response to different indirect tests is generally similar in patients with asthma and healthy athletes with EIB. Furthermore, the airway sensitivity to these tests is modified by the same pharmacotherapy used to treat asthma. In contrast, pharmacological agents such as methacholine, given by inhalation, act directly on smooth muscle to cause contraction. These "direct" tests have been used traditionally to identify airway hyperresponsiveness in clinical asthma but are less useful to diagnose EIB. The mechanistic differences between indirect and direct tests have helped to elucidate the events leading to airway narrowing in patients with asthma and elite athletes, while improving the clinical utility of these tests to diagnose and manage EIB.

Impulse oscillometry and free-running tests for diagnosing asthma and monitoring lung function in young children

BACKGROUND

Separating individuals with viral-induced wheezing from those with asthma is challenging, and there are no guidelines for children under 6 years of age. Impulse oscillometry, however, is feasible in 4-year-old children.

OBJECTIVE

To explore the use of impulse oscillometry in diagnosing and monitoring asthma in young children and evaluating treatment response to inhaled corticosteroid (ICS).

METHODS

A total of 42 children (median age 5.3 years, range 4.0-7.9 years) with physician-diagnosed asthma and lability in oscillometry were followed for 6 months after initiation of ICS treatment. All children performed the 6-minute free-running test and impulse oscillometry at 3 time points. After the baseline, they attended a second visit when they had achieved good asthma control and a third visit approximately 60 days after the second visit. A positive ICS response was defined as having greater than 19 points in asthma control test and no hyperreactivity on the third visit.

RESULTS

In total, 38 of 42 children responded to ICS treatment. Exercise-induced increases of resistance at 5 Hz decreased after ICS treatment (61% vs 18% vs 13.5%, P < .001), and running distance during the 6-minute test was lengthened (800 m vs 850 m vs 850 m, P = .001). Significant improvements in childhood asthma control scores occurred between the baseline and subsequent visits (21 vs 24 vs 24, P < .001) and acute physicians' visits for respiratory symptoms (1, (0-6) vs 0, (0-2), P = .001). Similar profiles were observed in children without aeroallergen sensitization and among those under 5 years of age.

CONCLUSION

Impulse oscillometry is a useful tool in diagnosing asthma and monitoring lung function in young children.

Comparison of methacholine and mannitol challenges: importance of method of methacholine inhalation

Background

Direct inhalation challenges (e.g. methacholine) are stated to be more sensitive and less specific for a diagnosis of asthma than are indirect challenges (e.g. exercise, non-isotonic aerosols, mannitol, etc.). However, data surrounding comparative sensitivity and specificity for methacholine compared to mannitol challenges are conflicting. When methacholine is inhaled by deep total lung capacity (TLC) inhalations, deep inhalation inhibition of bronchoconstriction leads to a marked loss of diagnostic sensitivity when compared to tidal breathing (TB) inhalation methods. We hypothesized that deep inhalation methacholine methods with resulting bronchoprotection may be the explanation for conflicting sensitivity/specificity data.

Methods

We reviewed 27 studies in which methacholine and mannitol challenges were performed in largely the same individuals. Methacholine was inhaled by dosimeter TLC methods in 13 studies and by tidal breathing in 14 studies. We compared the rates of positive methacholine (stratified by inhalation method) and mannitol challenges in both asthmatics and non-asthmatics.

Results

When methacholine was inhaled by TLC inhalations the prevalence of positive tests in asthmatics, 60.2% (548/910), was similar to mannitol, 58.9% (537/912). By contrast, when methacholine was inhaled by tidal breathing the prevalence of positive tests in asthmatics 83.1% (343/413) was more than double that of mannitol, 41.5% (146/351). In non-asthmatics, the two methacholine methods resulted in positive tests in 18.8% (142/756) and 16.2% (27/166) by TLC and TB inhalations respectively. This compares to an overall 8.3% (n = 76) positive rate for mannitol in 913 non-asthmatics.

Conclusion

These data support the hypothesis that the conflicting data comparing methacholine and mannitol sensitivity and specificity are due to the method of methacholine inhalation. Tidal breathing methacholine methods have a substantially greater sensitivity for a diagnosis of asthma than either TLC dosimeter methacholine challenge methods or mannitol challenge. Methacholine challenges should be performed by tidal breathing as per recent guideline recommendations. Methacholine (more sensitive) and mannitol (more specific) will thus have complementary diagnostic features.

Urinary and exhaled biomarkers of exercise-induced bronchoconstriction in atopic asthmatic children

BACKGROUND

Exercise-induced bronchoconstriction (EIB) reflects poor asthma control. Assessing noninvasive biomarkers associated with EIB could help to monitor patients in the pediatric age.

AIMS

To test exhaled and urinary biomarkers for assessing EIB in atopic asthmatic children.

METHODS

In 45 atopic patients (11.1 ± 1.8 years, 25 males) we measured the fractional exhaled nitric oxide (FE_NO ), its alveolar (CaNO), and bronchial (J'awNO) components corrected for the trumpet shape of the airways and axial NO diffusion (TMAD), concentrations of urinary adenosine and 8-hydroxy-2'-deoxyguanosine (8-OxodG), blood eosinophils count, total immunoglobulin E , skin prick tests, and baseline spirometry before a treadmill exercise challenge. Forty healthy control subjects participated solely to baseline measurements.

RESULTS

Patients yielded higher FE_NO and urinary adenosine concentrations than healthy controls. After the challenge, 18 patients (40%) had EIB; these patients had higher levels of CaNO, CaNO TMAD, and urinary adenosine than patients without EIB. Baseline spirometry, FE _NO , JawNO, JawNO TMAD, urinary 8-OxodG, allergy, and blood eosinophil counts were found similar in both groups. In multiple linear regression, the fall in FEV ₁ was explained by CaNO TMAD, urinary adenosine and blood eosinophil count, whereas the fall in FEF _25-75 was explained by CaNO TMAD and blood eosinophil count. Both CaNO TMAD ≥10.5 ppb and urinary adenosine ≥406 nmol/mmol Cr predicted a fall in FEV ₁ ≥10%, while only CaNO TMAD ≥10.5 ppb predicted a fall in FEF _25-75 ≥26%.

CONCLUSION

Concentrations of peripheral airway NO are complementary with urinary adenosine for assessing EIB and promising tools of asthma control in pediatric patients with the atopic phenotype.

The correlation of adenosine challenge test results with subsequent clinical course among young children with suspected asthma: a retrospective cohort study

AIM

Our aim was to evaluate the correlation of Adenosine monophosphate challenge test (AMP-PCW) results with the patients' subsequent clinical course.

METHODS

We performed a 6-year retrospective cohort study of young children with suspected asthma who underwent AMP-PCW test.

RESULTS

Fifty four children were included in the study (median age, 50.5 months; range, 26-90). AMP-PCW was positive in 35 (65%) children. During the 3-year follow-up period, among 22 of 35 patients in the positive AMP-PCW group and among 17 of 19 in the negative AMP-PCW group-prophylactic therapy was not changed. Prophylactic therapy was initiated or its dose was escalated in 12 of 13 (92.3%) of the children with a positive AMP-PCW test compared to none of the children with a negative challenge test (P < 0.001). Prophylactic therapy was discontinued in only one (7.6%) of the children with a positive test as compared to two (100%) of the children with a negative test (P < 0.001). There were significantly fewer severe asthma exacerbations during a 3-year follow-up period after the challenge test as compared to the preceding 3-year period both in children with a positive (from 34 to 9 total events, P = 0.01) or a negative challenge test (from 16 to 0 events P = 0.01). The severity of airway hyper responsiveness was found to associate with the number of severe asthma exacerbations (P = 0.04) and with a diagnosis of asthma during the following 3 years (P = 0.02).

CONCLUSIONS

AMP-PCW test results correlates with the subsequent clinical course of young children with suspected asthma performing the test.

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.

Impact of detecting and treating exercise-induced bronchoconstriction in elite footballers

Our aim was to evaluate the prevalence of exercise-induced bronchoconstriction (EIB) in elite football players and assess subsequent impact of therapy on airway health and exercise performance. 97 male professional football players completed an airway health assessment with a eucapnic voluntary hyperpnoea (EVH) challenge to diagnose EIB. Players demonstrating a positive result (EVH+) were prescribed inhaler therapy depending on severity, including inhaled corticosteroids and inhaled short-acting β2-agonists, and underwent repeat assessment after 9 weeks of treatment. Eight players (EVH+ n=3, EVH- n=5) completed a peak oxygen uptake (V'O2peak) test at initial and follow-up assessment. Out of the 97 players, 27 (28%) demonstrated a positive EVH result. Of these, 10 had no prior history (37%) of EIB or asthma. EVH outcome was not predictable by respiratory symptoms. Seven (24%) of the 27 EVH+ players attended follow-up and demonstrated improved post-challenge spirometry (forced expiratory volume in 1 s pre-test -22.9±15.4%, post-test -9.0±1.6%; p=0.018). At follow-up V'O2peak improved by 3.4±2.9 mL·kg-1·min-1 in EVH+ players compared to 0.1±2.3 mL·kg-1·min-1 in EVH- players. Magnitude of inference analysis indicated treatment was possibly beneficial (74%) for exercise capacity. Elite football players have a high EIB prevalence. Treatment with inhaler therapy reduces EIB severity.

Differences and similarities between bronchopulmonary dysplasia and asthma in schoolchildren

BACKGROUND

The long-term respiratory characteristics of ex-preterm children with bronchopulmonary dysplasia (BPD) are not established. The objective of this study was to describe hallmarks of BPD at school age in comparison to children with atopic asthma.

METHODS

This study was a cross-sectional descriptive comparative study in a hospital-based setting. Thirty schoolchildren diagnosed with BPD (10.4 years/born at 26.6 weeks' gestation) and 30 age- and sex-matched children with asthma and sensitized to airborne allergens (IgE >0.35 kU_A /L) were analyzed. Measurements included fraction of exhaled nitric oxide (FENO, ppb), dynamic and static lung function, and bronchial provocation with methacholine (PD:20) and mannitol (PD:15), as well as an evaluation of respiratory symptoms using the asthma control test (C-ACT).

RESULTS

Lung function measures (FEV1% 77 vs 84, FEV1/FVC% 85 vs 91, FEF50% 61 vs 80) and carbon monoxide diffusion capacity (DLCO%, 81 vs 88) were all reduced in children with BPD compared to asthma (P values <0.042). FENO values were also significantly lower in children with BPD (12 vs 23, P = 0.019). The proportion of positive methacholine tests (74% vs 93%, P = 0.14) was comparable between BPD and asthma. However, less responsiveness towards mannitol (19% vs 61%, P = 0.007) and fewer self-reported symptoms (C-ACT, median 26 vs 24, P = 0.003) were found in the BPD group.

CONCLUSION

Respiratory hallmarks of BPD at school-age were reduced lung function, limited responsiveness towards indirectly acting mannitol but hyper-responsiveness towards direct acting methacholine and impairment in diffusion capacity. Children with BPD displayed less evidence of airway inflammation compared with atopic asthma.

Eucapnic Voluntary Hyperpnea: Gold Standard for Diagnosing Exercise-Induced Bronchoconstriction in Athletes?

In athletes, a secure diagnos is of exercise-induced bronchoconstriction (EIB) is dependent on objective testing. Evaluating spirometric indices of airflow before and following an exercise bout is intuitively the optimal means for the diagnosis; however, this approach is recognized as having several key limitations. Accordingly, alternative indirect bronchoprovocation tests have been recommended as surrogate means for obtaining a diagnosis of EIB. Of these tests, it is often argued that the eucapnic voluntary hyperpnea (EVH) challenge represents the ‘gold standard’. This article provides a state-of-the-art review of EVH, including an overview of the test methodology and its interpretation. We also address the performance of EVH against the other functional and clinical approaches commonly adopted for the diagnosis of EIB. The published evidence supports a key role for EVH in the diagnostic algorithm for EIB testing in athletes. However, its wide sensitivity and specificity and poor repeatability preclude EVH from being termed a ‘gold standard’ test for EIB.

Effect of once-daily generic ciclesonide on exhaled nitric oxide in atopic children with persistent asthma

BACKGROUND

Ciclesonide (CIC) is an effective inhaled corticosteroid for treating asthmatic children. However, its effect on airway inflammation assessed by the fraction of exhaled nitric oxide (FENO) in children with persistent asthma is virtually unknown. We aimed to assess the effect of once-daily generic CIC, 80 or 160 μg, on FENO, lung function, asthma control and bronchial hyperresponsiveness, in atopic children with persistent asthma.

METHODS

This was a 12-week, randomised, double-blind, parallel-group study. Sixty children with mild-to-moderate persistent asthma were recruited. Changes in FENO, asthma control score, lung function (FEV1) and bronchial hyperresponsiveness to methacholine (BHR) were used to assess the effects of both CIC doses. Non-normally distributed variables were log-transformed to approximate normality, and parametric tests were used for comparisons within and between groups at baseline and after 12 weeks of treatment.

RESULTS

In the CIC 80 μg group, FENO decreased from 45.0 ppb (95% CI 37.8-53.7) to 32.7 ppb (95% CI 21.0-47.3) at the end of study (P=0.021), whereas in the CIC 160 μg group, FENO decreased from 47.3 ppb (95% CI 40.4-55.3) to 30.5 ppb (95% CI 24.1-38.7) (P<0.001). The difference between groups in FENO at the end of study was not significant (P=0.693). There was a significant improvement of asthma control with both CIC doses but there was no significant change in BHR or FEV1 in either group.

CONCLUSION

Once-daily generic ciclesonide (80 μg or 160 μg), for 12 weeks, is effective to improve airway inflammation and asthma control in atopic children with persistent asthma.

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.

Exhaled nitric oxide and other exhaled biomarkers in bronchial challenge with exercise in asthmatic children: current knowledge

The fractional concentration of exhaled nitric oxide (FENO), a known marker of atopic-eosinophilic inflammation, may be used as a surrogate to assess exercise-induced bronchoconstriction (EIB) in asthmatic children. The predictive value of baseline FENO for EIB appears to be influenced by several factors, including age, atopy, current therapy with corticosteroids and measurement technique. Nonetheless, FENO cut-off values appear to be able to rule out EIB. FENO levels decrease during EIB, apparently through neural mechanisms rather than by decreased airway-epithelial surface. Partition of FENO into proximal and peripheral contributions of the respiratory tract may improve our understanding on NO exchange during exercise and help to screen subjects prone to EIB. Other biomarkers of inflammation and oxidative stress contained in exhaled gases and exhaled breath condensate (EBC) may shed light on the pathophysiology of EIB. Exhaled breath temperature is a promising real-time measurement whose routine use for assessing EIB warrants further investigation.

Where to from here for exercise-induced bronchoconstriction: the unanswered questions

The role of epithelial injury is an unanswered question in those with established asthma and in elite athletes who develop features of asthma and exercise-induced bronchorestriction (EIB) after years of training. The movement of water in response to changes in osmolarity is likely to be an important signal to the epithelium that may be central to the onset of EIB. It is generally accepted that the mast cell and its mediators play a major role in EIB and the presence of eosinophils is likely to enhance EIB severity.

Airway hyperresponsiveness in asthma: mechanisms, clinical significance, and treatment

Airway hyperresponsiveness (AHR) and airway inflammation are key pathophysiological features of asthma. Bronchial provocation tests (BPTs) are objective tests for AHR that are clinically useful to aid in the diagnosis of asthma in both adults and children. BPTs can be either “direct” or “indirect,” referring to the mechanism by which a stimulus mediates bronchoconstriction. Direct BPTs refer to the administration of pharmacological agonist (e.g., methacholine or histamine) that act on specific receptors on the airway smooth muscle. Airway inflammation and/or airway remodeling may be key determinants of the response to direct stimuli. Indirect BPTs are those in which the stimulus causes the release of mediators of bronchoconstriction from inflammatory cells (e.g., exercise, allergen, mannitol). Airway sensitivity to indirect stimuli is dependent upon the presence of inflammation (e.g., mast cells, eosinophils), which responds to treatment with inhaled corticosteroids (ICS). Thus, there is a stronger relationship between indices of steroid-sensitive inflammation (e.g., sputum eosinophils, fraction of exhaled nitric oxide) and airway sensitivity to indirect compared to direct stimuli. Regular treatment with ICS does not result in the complete inhibition of responsiveness to direct stimuli. AHR to indirect stimuli identifies individuals that are highly likely to have a clinical improvement with ICS therapy in association with an inhibition of airway sensitivity following weeks to months of treatment with ICS. To comprehend the clinical utility of direct or indirect stimuli in either diagnosis of asthma or monitoring of therapeutic intervention requires an understanding of the underlying pathophysiology of AHR and mechanisms of action of both stimuli.

Past, present and future uses of methacholine testing

Methacholine challenge testing is a valuable diagnostic and research tool used by clinicians to assist in the diagnosis of asthma, and by researchers to understand disease pathophysiology and assess novel therapeutic efficacy. The use of methacholine challenge in asthma relates to its direct effect on airway smooth muscle (i.e., bronchoconstriction) as a measure of airway hyperresponsiveness, a cardinal feature of asthma. Airway hyperresponsiveness has been documented in other airway disorders, including chronic obstructive pulmonary disease, cystic fibrosis and allergic rhinitis; however, there is little clinical application of methacholine challenge in these conditions as a diagnostic or disease management tool. The authors will review the aspects of methacholine challenge testing, as they relate to asthma, and point out its usefulness in clinical research. A brief review of past (historical) uses and speculation as to the future uses of methacholine challenge will also be discussed.

Bronchoprovocation testing in asthma

This article covers the relationships between BHR and airway inflammation. Recent evidence suggests that various commonly used bronchoprovocation challenges (BPCs) differ in their potential to serve as inflammatory biomarkers. The response to direct stimuli depends on the smooth muscle's response to the chemical, whereas in indirect challenges, the reaction is caused by the smooth muscle's responsiveness to the mediators induced by the stimuli. The information obtained from studies with BPC has provided insights into the pathogenesis and pathophysiology of asthma, and the relationships between airway inflammation and bronchial hyper-responsiveness.

Diagnostic exercise challenge testing

This article reviews the diagnostic challenge methods-both exercise and surrogate-for diagnosis of exercise-induced bronchoconstriction (EIB) and EIB with known asthma. Indirect challenges that release the entire repertoire of mediators representative of EIB and asthma are more specific for diagnosis and are recommended over direct challenges such as methacholine challenge, which are sensitive but nonspecific. Self-reported history and empiric therapeutic trials are not adequate for diagnosis of EIB with or without known asthma. Objective pulmonary function documentation with bronchodilator reversibility or exercise or surrogate challenge are optimal for diagnosis of EIB or EIB with known asthma. Such objective pulmonary function documentation is optimal for the proper management and healthy lifestyle of the exercising athlete or individual.

Knowledge, attitude and skills before and after a module on pharmaceutical promotion in a Nepalese medical school

BACKGROUND

Pharmaceutical promotion is widespread and can impact prescribing by health professionals. Little research has been conducted on interactions between medical students and the pharmaceutical industry. Teaching about pharmaceutical promotion is inadequate. A survey showed that many schools spend only about two hours teaching this important topic while others spend around six hours. Recently a manual on understanding and responding to promotion has been published by Health Action International (HAI) and the World Health Organization (WHO). From April to August 2011 the department of Clinical Pharmacology at KIST Medical College, Lalitpur, Nepal conducted a module on pharmaceutical promotion for second year students based on the manual. The module used active learning strategies such as brainstorming sessions, role plays and group activities. The study worked on the hypothesis that a module on pharmaceutical promotion will be effective in improving the knowledge, attitude and skills of medical students regarding pharmaceutical promotion. The impact of the module on knowledge, attitude and skills was tested using a retrospective-pre questionnaire. The scores according to gender and method of financing of medical education before and after the module were compared using appropriate non-parametric tests.

RESULTS

Eighty-seven of the 100 second year students (87%) participated in the study. 47 were females (54%) and 39 (44.83%) were males and one did not state the gender. Seventy-seven students (88.5%) were self-financing while 9 were scholarship students. The median knowledge, attitude and skills score before the module were 9, 13 and 6 respectively while the overall score was 28. The scores increased significantly to 16, 15 and 14 respectively after the module while the overall score increased to 45. The median attitude scores and total scores were significantly higher among females both before and after the module. The scores did not vary with method of financing of medical education. All scores increased significantly at the end of the module.

CONCLUSIONS

The nine hour module held over a period of four months was effective in improving respondents' knowledge, attitudes and skills about pharmaceutical promotion. The module was not resource intensive and used resources already available in the institution. Similar modules can be considered in other medical and health profession schools in Nepal, South Asia and other developing countries.

Bronchial provocation testing: the future

PURPOSE OF REVIEW

Performing a bronchial provocation test (BPT) using a direct or indirect stimulus to identify bronchial hyper-responsiveness (BHR) reduces the possibility of over and under-diagnosis of asthma based on history and symptoms. This review discusses some long-held beliefs of BPTs to include or exclude a diagnosis of asthma or exercise-induced bronchoconstriction (EIB).

RECENT FINDINGS

A high frequency of negative methacholine tests has been reported in 240 patients given a diagnosis of asthma at the end of the study, many of whom had documented EIB. This suggests that a negative methacholine test should not be relied upon to rule out asthma. Further, a positive methacholine test alone should be interpreted with caution as it may reflect airway injury rather than asthma or EIB. Mannitol, an indirect stimulus, identified a similar prevalence of BHR to methacholine and identified more patients than a single exercise test in three studies. However, neither mannitol nor methacholine identified all patients with EIB. Mannitol has a higher specificity for a physician diagnosis of asthma than methacholine.

SUMMARY

It is likely that both a direct test and an indirect test result may be required in some patients in order to confirm or exclude a diagnosis of asthma with certainty.

Mannitol as an indirect bronchoprovocation test for the 21st century

OBJECTIVES

To review mannitol challenge data and advocate the approval of this testing modality in the United States.

DATA SOURCES

A literature review was performed using the MEDLINE database for English-language articles published between January 1, 1993, and July 31, 2009, using the following keywords: mannitol bronchoprovocation test, inhaled mannitol, inhaled mannitol and asthma, and inhaled mannitol and exercise-induced asthma.

STUDY SELECTION

Trials were selected that established the effect of mannitol as a bronchoprovocation challenge, explored mannitol's mechanism of action, and compared mannitol to other accepted bronchoprovocation challenges.

RESULTS

Mannitol has demonstrated the ability to detect airway hyperreactivity in individuals. The mechanism of action is through the release of mast cell mediators. The sensitivity and specificity compare well with other indirect challenge testing methods.

CONCLUSION

Mannitol is a polyol sugar that can be converted to a powdered form and encapsulated. Once encapsulated it can be inhaled and causes narrowing of the airways in susceptible individuals. Mannitol likely triggers the release of inflammatory and/or bronchospasm mediators, causing the smooth muscle of the airway to contract and resulting in airway narrowing. The magnitude of decrease in forced expiratory volume in 1 second and the dose of mannitol needed to provoke the airway response provide a readily measurable and clinically useful assessment of airway hyperreactivity. Mannitol challenge is an accepted testing method in Australia, Europe, and Korea. Acceptance of the mannitol challenge in the United States would complement existing methods for assessing bronchial hyperreactivity and likely improve patient care.

Assessment of inhaled corticosteroid treatment response in asthma using hypertonic histamine challenge-induced cough

BACKGROUND AND AIMS

Bronchial provocation tests may be utilised to monitor the efficacy of the corticosteroid treatment. Unfortunately, these measurements necessitate good patient cooperation during the spirometry. Coughing during such tests is related to the degree of the bronchoconstriction and occurs involuntarily, i.e. independent of patient cooperation. This study aimed to evaluate the utility of a hypertonic histamine challenge-induced cough in assessing the efficacy of inhaled corticosteroid treatment.

METHODS

A total of 16 steroid-naïve asthmatics and 10 non-asthmatic, symptomatic controls received 800-microg beclomethasone (Beclomet Easyhaler(R), Orion Ltd., Orion Pharma, Helsinki, Finland) via powder inhaler per day for 8 weeks. Videoed inhalation challenge with hypertonic histamine solution was performed before and after the treatment. Symptom questionnaire was completed before both challenges. The airway responsiveness to hypertonic histamine was expressed as the cumulative number of coughs divided by the final histamine concentration administered [coughs/concentration ratio (CCR)] and as the provocative concentration of histamine to induce a 20% fall in FEV(1)(PC(20)).

RESULTS

CCR [geometric mean; 95% confidence interval (CI)] of the asthmatic subjects decreased from 494 (209-1168) to 73.6 (29.8-182) coughs per mg/mL (P = 0.002). Their PC(20) levels were 1.31 (1.07-1.60) and 1.91 (1.33-2.74) mg/mL over the treatment period (P = 0.01). The symptom frequency also decreased significantly in the asthmatics (P = 0.039). There were no significant changes in PC(20) level, in CCR level or in symptom frequency in non-asthmatic subjects during the treatment.

CONCLUSIONS

Hypertonic histamine challenge-induced cough and PC(20) are sensitive measures in assessing the treatment effect in asthma. The cough response may be especially useful in subjects who cannot perform spirometry reliably.

Current and future use of the mannitol bronchial challenge in everyday clinical practice

OBJECTIVES

Asthma is a disease associated with inflammation, airway hyperresponsiveness (AHR) and airflow limitation. Clinical diagnosis and management of asthma often relies on assessment of lung function and symptom control, but these factors do not always correlate well with underlying inflammation. Bronchial challenge tests (BCTs) assess AHR, and can be used to assist in the diagnosis and management of asthma.

DATA SOURCE

Data presented at the symposium 'Use of inhaled mannitol for assessing airways disease' organised by the Allied Respiratory Professionals Assembly (9) of the European Respiratory Society (ERS) at the ERS Congress, Berlin 2008.

RESULTS

Indirect challenge tests such as exercise testing, hypertonic saline or adenosine 5'-monophosphate (AMP) are more specific though less sensitive than direct challenge tests (such as methacholine) for identifying patients with active asthma. Indirect BCTs may be used to diagnose exercise-induced bronchoconstriction or AHR consistent with active asthma, to evaluate AHR that will respond to treatment with anti-inflammatory drugs and to determine the effectiveness and optimal dosing of such therapy. An ideal indirect challenge test should be standardised and reproducible, and the test result should correlate with the degree of airway inflammation. The mannitol BCT provides a standardised and rapid point-of-need test to identify currently active asthma, and is clinically useful in the identification of patients with asthma who are likely to benefit from inhaled corticosteroid therapy.

CONCLUSION

In the future, mannitol BCT may be added to lung function and symptom assessment to aid in the everyday management of asthma.

Exercise-Induced Asthma Symptoms and Nighttime Asthma: Are They Similar to AHR?

Background. Asthma experienced during exercise and during the night is based on the presence of airway hyperresponsiveness (AHR). The aim of the present study was to examine whether AHR is a predictor of exercise-induced asthma (EIA) and nighttime symptoms. Material. We included 793 asthmatics subjects with symptoms and a positive asthma test. Results. Mean (SD) FEV1 was 93% (15), 71% had rhinitis, and 62% had atopy. Both EIA and nighttime symptoms were associated with AHR; however, when including other factors of importance in a multivariate analysis, logRDR was eliminated, whereas FEV1% pred (P < .001), smoking (P < .05), atopy (P < .001), sex (P < .001), and treatment (P < .01) were associated with having EIA while dyspnoea (P < .001), cough (P < .001), and eosinophils (P < .01) were associated with frequent night symptoms. The risk of having nighttime awakenings due to asthma was more than twofold higher among those with EIA symptoms than among those without symptoms (OR (CI95%) 2.77 (2.0–3.8) (P < .001)). In Conclusion. EIA and night symptoms are associated with AHR, but other factors of importance eliminated this close association. Night asthma is more closely associated with airway inflammation than AHR.

Diagnostic properties of inhaled mannitol in the diagnosis of asthma: a population study

BACKGROUND

A new indirect bronchial provocation test measuring airway responsiveness by using inhaled mannitol was recently introduced.

OBJECTIVE

The aim of this study was to examine the diagnostic properties of airway responsiveness to inhaled mannitol in the assessment of asthma in an unselected sample of young adults.

METHODS

Two hundred thirty-eight young adults randomly drawn from the nationwide civil registration list were challenged with inhaled, dry-powder mannitol. A respiratory specialist, blind to the test results, classified all 238 subjects with respect to the presence of asthma. The classification was based on respiratory symptoms, spirometric results, atopy, and fraction of exhaled nitric oxide values and response to inhaled beta(2)-agonists. On this basis, sensitivity, specificity, and predictive values were assessed to different cutoff values of the test. A receiver operating characteristic curve was constructed, and the accuracy of the test, defined as the area under the curve, was computed.

RESULTS

Fifty-one (21.4%) subjects had current asthma. Of 33 subjects with airway hyperresponsiveness to mannitol, 30 had current asthma. The specificity and sensitivity were 98.4% (95% CI, 96.2% to 99.4%) and 58.8% (95% CI, 50.7% to 62.6%), respectively. The positive predictive value (PPV) and negative predictive value (NPV) were 90.9% (95% CI, 78.4% to 96.8%) and 89.8 (95% CI, 87.7% to 90.7%), respectively. The area under the receiver operating characteristic curve was 0.89 (95% CI, 0.83-0.95).

CONCLUSIONS

In an unselected sample of young adults, bronchial provocation with inhaled dry-powder mannitol had a high diagnostic specificity for the diagnosis of asthma.

Unawareness and undertreatment of asthma: follow-up in a different geographic area in Denmark

BACKGROUND

Early detection and treatment of asthma is important to minimize morbidity and healthcare costs. The objective of this study was to investigate asthma awareness and management in a western society.

METHODS

In a random sample of 10 400 subjects aged 14-44 years, 686 (6.6%) reported symptoms of asthma in a standardized screening questionnaire. All 686 were evaluated by respiratory specialists and diagnosed by history, symptoms, lung function tests, bronchial challenges and allergy testing. Of these 686 participants, 69 (10%) had asthma alone, 205 (30%) had rhinitis alone and 217 (32%) had both asthma and rhinitis; 195 (28%) had nonasthmatic respiratory reports.

RESULTS

Awareness of asthma was found among 163 (57%) of the 286 asthmatics, and 204 (95%) had doctor-diagnosed rhinitis as well. In a multivariate regression analysis, comorbidity with rhinitis (beta = 0.489, P < 0.001), smoking (beta = -0.116, P < 0.01), doctor-diagnosed bronchitis (beta = 0.086, P < 0.05), and earlier emergency visits at hospital (beta = 0.147, P < 0.001) was significantly associated with awareness. A difference in awareness was found between those who had asthma and rhinitis (62.2%) and those who had asthma alone (40.6%) (P < 0.01). Inhaled corticosteroids (ICS) were used by 27% of those with asthma, including 12% who used both ICS and long-acting beta-agonist.

CONCLUSIONS

More than half of the persons with asthma were aware of their disorder; and the awareness was more likely in those with comorbidity of rhinitis. In general, asthma management was inadequate.

Provoked models of asthma: what have we learnt?

Asthma is a chronic inflammatory disease of the airways characterized by physiological abnormalities of variable airflow obstruction and airway hyperresponsiveness (AHR) to a wide variety of physical and inhaled chemical stimuli and the presence of symptoms. AHR is measured by challenging the airways with a variety of agonists and naturally occurring stimuli, which results in constriction of the airway smooth muscle, leading to airway narrowing and airflow limitation. There are two distinct mechanisms by which the airways can narrow to a constrictor stimulus and these are defined by the pathways they take to induce AHR. Direct stimuli are pharmacological agents administered exogenously (such as histamine or methacholine) that act 'directly' on specific receptors on the bronchial smooth muscle to cause constriction. The other mechanism by which the airway can narrow is via the inhalation of indirect stimuli, which include natural stimuli, such as allergen or exercise, and pharmacological agents such as adenosine monophosphate and hyper-osmotic agents (e.g. hypertonic saline or dry powder mannitol). These stimuli induce airway narrowing 'indirectly' by causing the endogenous release of mediators of bronchoconstriction from airway inflammatory cells. Provoked models of asthma have been extremely valuable in understanding the pathobiology of asthma, in aiding diagnosis, in helping to clarify the mechanisms of actions of effective drugs and in the development of new entities to treat asthma. Some provoked models are valuable clinically, particularly those that measure direct AHR, while others, particularly allergen challenge, have been used in animal models and in humans to study the mechanisms of allergen-induced airway inflammation and the associated physiological changes, as well in the development of new drugs for asthma. An emerging role for measurements of AHR is in the evaluation of the optimal treatment for patients with asthma.

8-Isoprostane in exhaled breath condensate and exercise-induced bronchoconstriction in asthmatic children and adolescents

BACKGROUND

Exercise-induced bronchoconstriction (EIB) in the asthmatic child is associated with persistent airway inflammation and poor disease control. EIB could arise partly from airway oxidative stress. Exhaled breath condensate (EBC) levels of 8-isoprostane (IsoP), which is a known marker of oxidative stress, might therefore be helpful for monitoring asthma noninvasively.

METHODS

We recruited 46 asthmatic children and adolescents 6 to 17 years of age (29 boys), all of whom underwent lung function testing, measurement of the fractional concentration of exhaled nitric oxide (FENO), and collection of EBCs for 8-IsoP measurement before and after exercise challenge. FENO was measured before exercise and 5 min and 20 min after exercise. Spirometry was repeated 1, 5, 10, 15, and 20 min after exercise.

RESULTS

Baseline 8-IsoP levels (but not baseline FENO levels) correlated with the fall in FEV(1) 5 min after exercise (r = - 0.47; p = 0.002). 8-IsoP levels measured after exercise remained unchanged from baseline levels; conversely, FENO levels decreased in parallel with the decline in FEV(1) at 5 min (r = 0.44; p = 0.002). The mean baseline 8-IsoP concentrations were higher in patients with EIB (n = 12) than in those without EIB (n = 34; 44.9 pg/mL [95% confidence interval (CI), 38.3 to 51.5] vs 32.3 pg/mL [95% CI, 27.6 to 37.0], respectively; p < 0.01). No difference was found in the mean baseline FENO between groups (with EIB group: 38.7 ppb; 95% CI, 24.5 to 61.1; without EIB group: 29.1 ppb; 95% CI, 22.0 to 38.4).

CONCLUSIONS

Increased 8-IsoP concentrations in EBC samples of asthmatic children and adolescents with EIB suggest a role for oxidative stress in bronchial hyperreactivity.

Provocative challenges to help diagnose and monitor asthma: exercise, methacholine, adenosine, and mannitol

PURPOSE OF REVIEW

To review bronchial provocations tests used in the measurement of bronchial hyperresponsiveness to help in the diagnosis of asthma.

RECENT FINDINGS

The bronchial provocations tests reviewed include exercise, methacholine, AMP and mannitol, with reference to methodology and monitoring of treatment.

SUMMARY

Methacholine is used for identifying bronchial hyperresponsiveness and to guide treatment. Exercise is used as a bronchial provocation test because demonstrating prevention of exercise-induced asthma is an indication for use of a drug. Both of these tests are being used to study tolerance to beta2 agonists. There is increasing use of eucapnic voluntary hyperpnea as a surrogate bronchial provocation test for exercise to identify exercise-induced asthma, particularly in athletes. For methacholine and AMP there is concern about the different breathing patterns used to inhale these aerosols and the impact they have on the cutoff point for identifying bronchial hyperresponsiveness. A new test that uses a kit containing prepacked capsules of different doses of mannitol and a delivery device is discussed. There is increasing interest in using tests that act indirectly by release of mediators because the bronchial hyperresponsiveness itself is an indicator of the presence of inflammation. Since treatment of inflammation leads to loss of bronchial hyperresponsiveness to indirect stimuli, these tests are well suited to identify success of treatment.

Methods used in clinical development of novel anti-asthma therapies

In recent years, it has become increasingly important to get as much as possible information on clinical efficacy already in the early phases of drug development. For proof of concept (POC) studies testing novel anti-inflammatory drugs in asthma, there are several validated exacerbation models, inducing various aspects of the airway inflammation and airway responsiveness. The choice of the appropriate asthma model depends on the drug's targets within the inflammatory process. For adequate assessment of the drug's anti-inflammatory potential, it is crucial to choose adequate (surrogate) biomarkers. Ideally, these should include measures of airway response, central and peripheral airway inflammation and airway hyperresponsiveness. Overall, there are validated non-invasive sampling techniques for the measurement of inflammatory markers in asthma that can be applied as outcome parameters in early clinical trials. If adequately implemented, these measurements can provide early indication of proof of pharmacological and potential therapeutic efficacy-even in first administration to humans.