Reproducibility of non-specific bronchial challenge in adults: implications for design, analysis and interpretation of clinical and epidemiological studies

Mechanisms of airway hyper-responsiveness in asthma: the past, present and yet to come

Airway hyper-responsiveness (AHR) has long been considered a cardinal feature of asthma. The development of the measurement of AHR 40 years ago initiated many important contributions to our understanding of asthma and other airway diseases. However, our understanding of AHR in asthma remains complicated by the multitude of potential underlying mechanisms which in reality are likely to have different contributions amongst individual patients. Therefore, the present review will discuss the current state of understanding of the major mechanisms proposed to contribute to AHR and highlight the way in which AHR testing is beginning to highlight distinct abnormalities associated with clinically relevant patient populations. In doing so we aim to provide a foundation by which future research can begin to ascribe certain mechanisms to specific patterns of bronchoconstriction and subsequently match phenotypes of bronchoconstriction with clinical phenotypes. We believe that this approach is not only within our grasp but will lead to improved mechanistic understanding of asthma phenotypes and we hoped to better inform the development of phenotype-targeted therapy.

Anti-oxidant N-acetylcysteine diminishes diesel exhaust-induced increased airway responsiveness in person with airway hyper-reactivity

BACKGROUND

Inhalation of diesel exhaust (DE) at moderate concentrations causes increased airway responsiveness in asthmatics and increased airway resistance in both healthy and asthmatic subjects, but the effect of baseline airway responsiveness and anti-oxidant supplementation on this dynamic is unknown.

OBJECTIVES

We aimed to determine if changes in airway responsiveness due to DE are attenuated by thiol anti-oxidant supplementation, particularly in those with underlying airway hyper-responsiveness.

METHODS

Participants took N-acetylcysteine (600 mg) or placebo capsules three times daily for 6 days. On the last of these 6 days, participants were exposed for 2 h to either filtered air (FA) or DE (300 μg/m(3) of particulate matter smaller than 2.5 microns). Twenty-six non-smokers were studied under each of three experimental conditions (filtered air with placebo, diesel exhaust with placebo, and diesel exhaust with N-acetylcysteine) using a randomized, double-blind, crossover design, with a 2-week washout between conditions. Methacholine challenge was performed pre-exposure (baseline airway responsiveness) and post-exposure (effect of exposure).

RESULTS

Anti-oxidant supplementation reduced baseline airway responsiveness in hyper-responsive individuals by 20% (p = 0.001). In hyper-responsive individuals, airway responsiveness increased 42% following DE compared with FA (p = 0.03) and this increase was abrogated with anti-oxidant supplementation (diesel exhaust with N-acetylcysteine vs. filtered air with placebo, p = 0.85).

CONCLUSIONS

Anti-oxidant (N-acetylcysteine) supplementation protects against increased airway responsiveness associated with DE inhalation and reduces need for supplement bronchodilators in those with baseline airway hyper-responsiveness. Individuals with variants in genes of oxidative stress metabolism when exposed to DE are protected from increases in airway responsiveness if taking anti-oxidant supplementation.

Randomised placebo-controlled study of the effect of paracetamol on asthma severity in adults

OBJECTIVE

To investigate the effect of regular paracetamol on bronchial hyper-responsiveness (BHR) and asthma control in adult asthma.

SETTING

Single research-based outpatient clinic.

PARTICIPANTS

94 adults with mild-to-moderate asthma received randomised treatment; 85 completed the study. Key inclusion criteria were age 18-65 years, forced expiratory volume in 1 s (FEV1) >70% predicted, provocation concentration of methacholine causing a 20% reduction in FEV1 (PC20) between 0.125 and 16 mg/mL. Key exclusion criteria included an asthma exacerbation within the previous 2 months, current regular use of paracetamol, use of high-dose aspirin or non-steroidal anti-inflammatory drugs, current or past cigarette smoking >10 pack-years.

INTERVENTIONS

In a 12-week randomised, double-blind, placebo-controlled, parallel-group study, participants received 12 weeks of 1 g paracetamol twice daily or placebo twice daily.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome variable was BHR, measured as the PC20 at week 12. Secondary outcome variables included FEV1, fractional exhaled nitric oxide (FeNO) and asthma control questionnaire (ACQ) score.

RESULTS

At 12 weeks, the mean (SD) logarithm base two PC20 was 1.07 (2.36) in the control group (N=54) and 0.62 (2.09) in the paracetamol group (N=31). After controlling for baseline PC20, the mean difference (paracetamol minus placebo) was -0.48 doubling dose worsening in BHR in the paracetamol group (95% CI -1.28 to 0.32), p=0.24. There were no statistically significant differences (paracetamol minus placebo) in log FeNO (0.09 (95% CI -0.097 to 0.27)), FEV1 (-0.07 L (95% CI -0.15 to 0.01)) or ACQ score (-0.04 (95% CI -0.27 to 0.18)).

CONCLUSIONS

There was no significant effect of paracetamol on BHR and asthma control in adults with mild-to-moderate asthma. However, the study findings are limited by low power and the upper confidence limits did not rule out clinically relevant adverse effects.

TRIAL REGISTRATION

Australia New Zealand Clinical Trials Registry Number: NZCTR12609000551291.

Variability of methacholine bronchoprovocation and the effect of inhaled corticosteroids in mild asthma

BACKGROUND

The methacholine challenge test quantifies airway hyper-responsiveness, which is measured by the provocative concentration of methacholine causing a 20% decrease in forced expiration volume in 1 second (PC20). The dose-response effect of inhaled corticosteroids (ICS) on PC20 has been inconsistent and within-patient variability of PC20 is not well established.

OBJECTIVE

To determine the effect of high- vs low-dose ICS on PC20 and within-patient variability in those with repeated measurements of PC20.

METHODS

A randomized, double-masked, crossover trial was conducted in patients with asthma on controller medications with PC20 of 8 mg/mL or lower (n = 64) to evaluate the effect of high-dose (1,000 μg/d) vs low-dose (250 μg/d) fluticasone for 4 weeks on PC20. In addition, the variability of PC20 was assessed in participants who underwent 2 or 3 PC20 measurements on the same dose of ICS (n = 27) over a 4-week interval.

RESULTS

Because there was a significant period effect, dose comparison of the change in PC20 was assessed in the first treatment period. There was no significant difference in the change in PC20 for high- vs low-dose ICS (39% vs 30% increase, respectively; P = .87). The within- and between-participant variances for log PC20 were 0.84 and 0.96, respectively, with an intra-class correlation of 0.53, and 37% of participants had more than 2 doubling dose changes in PC20 in those with repeated measurements.

CONCLUSION

The effect of ICS on PC20 is not dose dependent at fluticasone levels of 250 and 1,000 μg/d. Interpersonal variability for PC20 is large. A lack of precise measurements should be taken into account when interpreting any change in PC20.

Bronchial hyperresponsiveness in an adult population in Helsinki: decreased FEV1 , the main determinant

Introduction

Bronchial hyperresponsiveness (BHR) elevates the risk for development of respiratory symptoms and accelerates the decline in forced expiratory volume in the first second (FEV₁). We thus aimed to assess the prevalence, determinants and quantity of BHR in Helsinki.

Objectives

This study involved 292 randomly selected subjects age 26–66 years, women comprising 58%.

Methods

Following a structured interview, a spirometry, a bronchodilation test, and a skin-prick test, we assessed a bronchial challenge test with inhaled histamine using a dosimetric tidal breathing method. Results included the provocative dose inducing a decrease in FEV₁ by 15% (PD₁₅FEV₁) and the dose-response slope. For statistical risk factor-analyses, the severity of BHR was considered; PD₁₅ values ≤1.6 mg (BHR) and ≤0.4 mg [moderate or severe BHR (BHR_ms)] served as cut-off levels.

Results

BHR presented in 21.2% and BHR_ms in 6.2% of the subjects. FEV₁ < 80% of predicted [odds ratio (OR) 4.09], airway obstruction (FEV₁/forced vital capacity < 88% of predicted) (OR 4.33) and history of respiratory infection at age <5 (OR 2.65) yielded an increased risk for BHR as ORs in multivariate analysis. For BHR_ms, the determinants were decreased FEV₁ below 80% of predicted (OR 27.18) and airway obstruction (OR 6.16). Respiratory symptoms and asthma medication showed a significant association with BHR.

Conclusions

Of the adult population of Helsinki, 21% showed BHR to inhaled histamine. The main determinants were decreased FEV₁ and airway obstruction. Quantitative assessment of BHR by different cut-off levels provides a tool for characterization of phenotypes of airway disorders in epidemiologic and clinical studies.

Please cite this paper as: Juusela M, Pallasaho P, Sarna S, Piirilä P, Lundbäck B and Sovijärvi A. Bronchial hyperresponsiveness in an adult population in Helsinki: decreased FEV₁, the main determinant. Clin Respir J 2013; 7: 34–44.

Steroid sparing effects of intranasal corticosteroids in asthma and allergic rhinitis

BACKGROUND

Treating allergic rhinitis may have a downstream anti-inflammatory effect on the lower airways. We conducted a dose ranging study in asthma and persistent allergic rhinitis to evaluate if intranasal corticosteroids exhibit a sparing effect on the dose of inhaled corticosteroid.

METHODS

Twenty five participants were randomized to receive two weeks of 100 microg/day (Low dose) or 500 microg/day (High dose) of inhaled fluticasone propionate both with intranasal placebo; or inhaled fluticasone 100 microg/day with intranasal fluticasone 200 microg/day (Combined) in a double-blind cross-over fashion.

RESULTS

Low dose fluticasone produced a shift of 1.20 doubling-dilutions (95% CI, 0.63, 1.77); Combined fluticasone, 1.79 doubling-dilutions (95% CI, 0.77, 2.80) and high dose fluticasone, 2.01 doubling-dilutions (95% CI, 1.42, 2.61) in methacholine PC(20) from respective baselines. There was a significant difference between high and low doses: 0.82 doubling dilutions (95%CI, 0.12, 1.50) but not between combined and low dose 0.58 doubling dilutions (95% CI, -0.78, 1.95). Combined treatment alone produced improvements in peak nasal inspiratory flow (P < 0.001), rhinitis quality of life (P = 0.004) and nasal NO (P = 0.01); reduced blood eosinophil count (P = 0.03), and serum eosinophil cationic protein (P = 0.02). All treatments significantly improved tidal NO, FEV(1) and asthma quality of life.

CONCLUSIONS

High-dose fluticasone was superior to low dose fluticasone for methacholine PC20, demonstrating room for further improvement. Combined treatment was not significantly different from low dose fluticasone and we could not demonstrate a steroid sparing effect on methacholine PC20. Combined treatment alone produced improvements in upper airway outcomes and suppressed systemic inflammation but not adrenal function.

Effect of oral magnesium supplementation on measures of airway resistance and subjective assessment of asthma control and quality of life in men and women with mild to moderate asthma: a randomized placebo controlled trial

BACKGROUND

Epidemiological data shows low dietary magnesium(Mg) may be related to incidence and progression of asthma.

OBJECTIVE

To determine if long term(6.5 month) treatment with oral Mg would improve asthma control and increase serum measures of Mg status in men and women with mild-to-moderate asthma.

SUBJECTS

55 males and females aged 21 to 55 years with mild to moderate asthma according to the 2002 National Heart, Lung, and Blood Institute(NHLBI) and Asthma Education and Prevention Program(NAEPP) guidelines and who used only beta-agonists or inhaled corticosteroids(ICS) as asthma medications were enrolled.

DESIGN

Subjects were randomly assigned to consume 340 mg(170 mg twice a day) of Mg or a placebo for 6.5 months.

MEASUREMENTS

Multiple measures of Mg status including serum, erythrocyte, urine, dietary, ionized and IV Mg were measured.

OBJECTIVE

markers of asthma control were: methacholine challenge test(MCCT) and pulmonary function test(PFT) results. Subjective validated questionnaires on asthma quality of life(AQLQ) and control(ACQ) were completed by participants. Markers of inflammation, including c-reactive protein(CRP) and exhaled nitric oxide(eNO) were determined.

RESULTS

The concentration of methacholine required to cause a 20% drop in forced expiratory volume in in minute(FEV(1)) increased significantly from baseline to month 6 within the Mg group. Peak expiratory flow rate(PEFR) showed a 5.8% predicted improvement over time(P = 0.03) in those consuming the Mg. There was significant improvement in AQLQ mean score units(P < 0.01) and in overall ACQ score only in the Mg group(P = 0.05) after 6.5 months of supplementation. Despite these improvements, there were no significant changes in any of the markers of Mg status.

CONCLUSION

Adults who received oral Mg supplements showed improvement in objective measures of bronchial reactivity to methacholine and PEFR and in subjective measures of asthma control and quality of life.

Bronchial hyperresponsiveness in a population of north Finland with no previous diagnosis of asthma or chronic bronchitis assessed with histamine and methacholine tests

OBJECTIVES

To assess the prevalence of bronchial hyperresponsiveness (BHR) in a population of north Finland among subjects with no previous diagnosis of asthma or chronic bronchitis by using histamine and methacholine challenges. The agreement between the methods was also evaluated.

STUDY DESIGN

An epidemiological study assessing the prevalence of BHR measured with 2 direct dosimetric challenge methods. METHODS; Seventy-nine randomly selected subjects (21-73 years) were studied; 67% had respiratory or allergic symptoms. The baseline spirometry was normal or showed mild obstruction. Bronchial challenges to methacholine and histamine were performed on each subject in a randomized order. Provocative doses inducing the decrease of FEV1 by 15% and 20% (PD15FEV1 and PD20FEV1) and dose response ratios (DDR) were calculated for both tests. RESULTS; BHR with the methacholine test (PD20FEV1 < or = 2.6 mg) was found in 20% and with the histamine test (PD15FEV1 < or = 1.6 mg) in 28% of subjects; the agreement was 80% (kappa 0.45; 95% CI 0.23-0.68). In staging the severity of BHR the methods had a good agreement (weighted kappa 0.64; CI 95% 0.46-0.82). Prevalence of BHR fulfilling the criteria of the both methods was 14%.

CONCLUSIONS

The findings suggest that the prevalence of BHR in the population of north Finland with no previous diagnosis of asthma or chronic bronchitis is at least 14%, probably around 20%, assessed by histamine and methacholine challenge methods. The methods have a good agreement to be used for classifying the severity of BHR.

Problems in using incidence to analyze risk factors in follow-up studies

The most common practice to analyze epidemiological follow-up studies is to analyze risk factors of new, i.e. incident, cases of disease. However, analysis of incidence assumes that diseases exist in true dichotomies, which is unlikely to be true. It has also recently been shown that in many typical situations it is very difficult to separate the association between risk factors of disease at baseline and during follow-up using analyses of incidence. Situation is especially problematic for diseases that have large misclassification and low incidence, like asthma. We suggest that reliance on analysis of incidence may be a major obstacle into discovering causes of such disease. Only with greater attention into how to define and how to analyze prospective studies are we likely to learn sufficiently of risk factors of such disease to finally arrive at means for their prevention.

Effect of aspirin on airway inflammation and pulmonary function in patients with persistent asthma

BACKGROUND

Aspirin can cause bronchoconstriction in some asthmatic patients through increased production of proinflammatory mediators, particularly leukotrienes. However, recent in vivo evidence has suggested that aspirin also triggers the production of lipoxins, which act as natural antagonists of prostaglandins and leukotrienes. Aside from patients with known aspirin-sensitive asthma, physicians have avoided the use of aspirin in asthmatic patients in general because it was believed that this agent might precipitate worsening of their condition.

OBJECTIVE

We sought to establish the effect of aspirin on pulmonary inflammation and function in patients with persistent asthma.

METHODS

After withdrawal of their usual anti-inflammatory medication, patients with mild-to-moderate persistent asthma undertook double-blind, randomized, crossover treatment with 75 mg/d aspirin and placebo for 3 weeks each. Treatment evaluation included histamine challenge, spirometry, impulse oscillometry, total and alveolar exhaled nitric oxide measurement, and serum thromboxane B2 and 15-epilipoxin A4 levels.

RESULTS

Fifteen patients completed the trial. Compared with placebo, there were no differences in histamine PC(20) values (0.17 doubling-dilution shift; 95% CI, -0.38 to 0.73; P = 1), exhaled nitric oxide levels (0.95-fold change; 95% CI, 0.45-2.00; P = 1), or any other inflammatory, spirometric, or oscillometry measurements. Aspirin led to a significant decrease in thromboxane B2 levels (17.53-fold difference; 95% CI, 5.46-56.49; P < .001). Baseline 15-epilipoxin A4 levels were increased at 4.88 ng/mL, and there was no increase with aspirin versus placebo (0.99-fold difference; 95% CI, 0.79-1.24; P = 1).

CONCLUSION

In this preliminary study of 15 patients, low-dose aspirin did not lead to increased 15-epilipoxin A4 synthesis or alter inflammatory markers in patients with mild-to-moderate persistent asthma.

Bronchial responsiveness in bakery workers: relation to airway symptoms, IgE sensitization, nasal indices of inflammation, flour dust exposure and smoking

BACKGROUND

Bronchial hyperresponsiveness (BHR) is common in bakery workers. The relation between bronchial responsiveness measured with a tidal breathing method and smoking, airway symptoms, IgE-sensitization, nasal indices of inflammation and flour dust exposure have been studied with bronchial responsiveness expressed as a continuous outcome.

MATERIAL AND METHODS

Bakery workers (n = 197) were subjected to interviews, questionnaires, allergy tests, workplace dust measurements and bronchial metacholine provocation. Eosinophil cationic protein (ECP) and alpha(2)-macroglobulin were measured in nasal lavage. Bronchial responsiveness was expressed as slope(conc), a measurement based on regressing the per cent reduction in FEV(1) at each provocation step.

RESULTS

BHR expressed as slope(conc) was associated with smoking (P = 0.009), asthma symptoms at work (P = 0.001), and occupational IgE sensitization (P = 0.048). After adjusting for baseline lung function the association between BHR and IgE sensitization was no longer present. We demonstrated an association between nasal ECP and BHR (slope(conc) < 3: P = 0.012), but not to alpha(2)-macroglobulin in nasal lavage. No association was seen between BHR and current exposure level of flour dust, number of working years in a bakery or a history of dough-making.

CONCLUSION

BHR is related to baseline lung function, work-related asthma symptoms, smoking and nasal eosinophil activity, but not to occupational IgE sensitization and current flour dust exposure when measured with metacholine provocation. The slope(conc) expression seems to be a useful continuous outcome in bronchial responsiveness testing.

An in vivo and in vitro comparison of inhaled steroid delivery via a novel vortex actuator and a conventional valved holding chamber

BACKGROUND

Valved holding chambers improve delivery of inhaled corticosteroids to the lung but are bulky in design. A novel compact vortex actuator device has therefore been developed.

OBJECTIVES

To compare the in vitro and in vivo performance of a novel compact vortex actuator (the Neohaler [NH]) vs a conventional small-volume valve holding chamber (the AeroChamber Plus [AP].

METHODS

Seventeen asthmatic patients completed the study per protocol, receiving 4 weeks each of 100 microg/d (50-microg formulation) or 400 microg/d (100-microg formulation) of hydrofluoroalkane beclomethasone dipropionate via the NH or AP devices in a randomized crossover, double-blind, double-dummy, placebo-controlled design. The doubling dilution (dd) shift in methacholine provocation concentration that caused a decrease in forced expiratory volume in 1 second of 20% (primary outcome) was used to evaluate anti-inflammatory effects and adrenal function to measure systemic exposure. The fine particle (<4.7 tm) dose was evaluated using an Andersen Cascade Impactor.

RESULTS

A total of 100 microg of hydrofluoroalkane beclomethasone dipropionate via the NH and AP produced 0.95-dd (95% confidence interval [CI], 0.44-1.45; P = .006) and 0.45-dd (95% CI, -0.16 to 1.06; P = .83) improvements from baseline in methacholine provocation concentration that caused a decrease in forced expiratory volume in 1 second of 20%, respectively, with no statistically significant difference between devices: 0.50 dd (95% CI, -0.25 to 1.24; P = .18). At 400 microg/d, 1.08-dd (95% CI, 0.49-1.67; P = .006) and 0.85-dd (95% CI, 0.32-1.39; P = .02) improvements were found for the NH and AP, respectively, with a 0.23-dd difference (95% CI, -0.28 to 0.74; P = .36) between devices. No adrenal suppression occurred with either device. The in vitro fine particle dose was 39.1 microg for the NH and 39.0 microg for the AP with the 100-microg formulation and 26.0 g and 25.2 microg, respectively, with the 50-microg formulation.

CONCLUSIONS

Delivering hydrofluoroalkane beclomethasone dipropionate via the NH and AP attenuates asthmatic airway inflammation to a comparable degree and produces a similar in vitro fine particle dose profile.

Intensity of bronchial hyperresponsiveness and asthma relapse risk in the young adult

BACKGROUND

The evolution of asthma starting in childhood varies and depends on a series of factors (atopy, allergens, and environmental irritants, etc). Treatment may influence the evolution of the disease and even cause the symptoms to disappear. However, there remains a risk of relapse years later.

OBJECTIVES

To assess the role of bronchial hyperresponsiveness in asthma relapse in young adulthood in patients with symptoms that disappeared after treatment prescribed in childhood.

MATERIAL AND METHODS

To determine the evolution of asthma and patients' personal opinions, 78 patients were sent a questionnaire several years after having been discharged without symptoms in the previous 2 years, and without the need for medication. The methacholine test was used to evaluate bronchial hyperresponsiveness at discharge. The 40 patients who correctly completed the questionnaire were divided into three groups according to the methacholine dose required to obtain a 20 % decrease in forced expiratory volume in 1 second (PD20): group 1 (15 patients), < 1000microg; group 2 (10 patients) between 1001 and 2000 microg; and group 3 (15 patients) > 2100 microg. The mean age at discharge was 16 years (range 13-25 years) versus 26 years at the time of response (range 18-33 years), with a similar distribution in all three groups. Age at disease onset, with estimation of severity, age at the first visit and at the start of treatment, and respiratory function were evaluated.

RESULTS

Thirty of the interviewed patients considered themselves to be cured. Seven of the patients (three in group 1, one in group 2, and three in group 3) did not consider themselves to be cured, although their symptoms were minimal and they rarely used medication. Health status was described as "regular" with sporadic symptoms by one patient in each group. No correlation with methacholine response was observed.

CONCLUSION

No relationship was found between the degree of bronchial hyperresponsiveness and the risk of relapse in young adults who suffered asthma in childhood.