Provocative dose of methacholine causing a 20% drop in FEV1 should be used to interpret methacholine challenge tests with modern nebulizers

A new tidal breathing measurement device detects bronchial obstruction during methacholine challenge test

PURPOSE

Bronchial hyperresponsiveness (BHR), a hallmark of bronchial asthma, is typically diagnosed through a methacholine inhalation test followed by spirometry, known as the methacholine challenge test (MCT). While spirometry relies on proper patients' cooperation and precise execution of forced breathing maneuvers, we conducted a comparative analysis with the portable nanomaterial-based sensing device, SenseGuard™, to non-intrusively assess tidal breathing parameters.

MATERIALS AND METHODS

In this prospective study, 37 adult participants with suspected asthma underwent sequential spirometry and SenseGuard™ measurements after inhaling increasing methacholine doses.

RESULTS

Among the 37 participants, 18 were MCT responders, 17 were non-responders and 2 were excluded due to uninterpretable data. The MCT responders exhibited a significant lung function difference when comparing the change from baseline to maximum response. This was evident through a notable decrease in forced expiratory volume in 1 ​s (FEV1) levels in spirometry, as well as in prominent changes in tidal breathing parameters as assessed by SenseGuard™, including the expiratory pause time (Trest) to total breath time (Ttot) ratio, and the expiratory time (Tex) to Ttot ratio. Notably, the ratios Trest/Ttot (∗p ​= ​0.02), Tex/Ttot (∗p ​= ​0.002), and inspiratory time (Tin) to Tex (∗p ​= ​0.04) identified MCT responders distinctly, corresponding to spirometry (∗p ​< ​0.0001).

CONCLUSIONS

This study demonstrates that tidal breathing assessment using SenseGuard™ device reliably detects clinically relevant changes of respiratory parameter during the MCT. It effectively distinguishes between responders and non-responders, with strong agreement to conventional spirometry-measured FEV1. This technology holds promise for monitoring clinical respiratory changes in bronchial asthma patients pending further studies.

Severe bronchial hyperresponsiveness along with house dust mite allergy indicates persistence of asthma in young children

BACKGROUND

Significant risk factors for persistence of asthma later in life are family history of allergies, early allergic sensitization and bronchial hyperresponsiveness (BHR). The evolution of BHR in young children without allergic sensitization and with house dust mite allergy (HDM) was investigated.

METHODS

In this retrospective analysis, electronic charts of 4850 young children with asthma and wheezy bronchitis between 2005 and 2018 were reviewed in order to study all patients ≤6 years with BHR assessed by methacholine provocation tests (MCT) at least once (n = 1175). Patients with more than two follow-up measurements were divided in group 1 (no allergic sensitization; n = 110) and group 2 (HDM allergy; n = 88). Additionally, skin prick test, exhaled nitrite oxide (eNO), and asthma treatment were analyzed.

RESULTS

Forty-seven patients of group 1 aged median 4.3 years and 48 patients of group 2 aged median 4.7 years showed initially severe BHR <0.1 mg. At follow-up, patients with HDM were more likely to show persistence of severe BHR than non-sensitized patients (severe BHR group 1: n = 5 (10.6%) vs. group 2: n = 21 (43.8%), p < .001). In addition, 89.4% of group 1 had mild to moderate or no BHR, compared to only 56.2% of group 2. There was a significant difference in eN0 (median group 1: 9 ppb vs. group 2: 26 ppb, p < .001), at last follow-up. Age, sex, and asthma therapy had no effect on BHR.

CONCLUSION

In young children without sensitization BHR normalizes, whereas HDM allergy indicates a persistence of asthma beyond infancy.

Epithelial cell responses to rhinovirus identify an early-life-onset asthma phenotype in adults

BACKGROUND

The study of pathogenic mechanisms in adult asthma is often marred by a lack of precise information about the natural history of the disease. Children who have persistent wheezing (PW) during the first 6 years of life and whose symptoms start before age 3 years (PW+) are much more likely to have wheezing illnesses due to rhinovirus (RV) in infancy and to have asthma into adult life than are those who do not have PW (PW-).

OBJECTIVE

Our aim was to determine whether nasal epithelial cells from PW+ asthmatic adults as compared with cells from PW- asthmatic adults show distinct biomechanistic processes activated by RV exposure.

METHODS

Air-liquid interface cultures derived from nasal epithelial cells of 36-year old participants with active asthma with and without a history of PW in childhood (10 PW+ participants and 20 PW- participants) from the Tucson Children's Respiratory Study were challenged with a human RV-A strain (RV-A16) or control, and their RNA was sequenced.

RESULTS

A total of 35 differentially expressed genes involved in extracellular remodeling and angiogenesis distinguished the PW+ group from the PW- group at baseline and after RV-A stimulation. Notably, 22 transcriptomic pathways showed PW-by-RV interactions; the pathways were invariably overactivated in PW+ patients, and were involved in Toll-like receptor- and cytokine-mediated responses, remodeling, and angiogenic processes.

CONCLUSIONS

Asthmatic adults with a history of persistent wheeze in the first 6 years of life have specific biomolecular alterations in response to RV-A that are not present in patients without such a history. Targeting these mechanisms may slow the progression of asthma in these patients.

Methacholine challenges: comparison of different tidal breathing challenge methods

Tidal-breathing methacholine challenges are now recommended by guidelines, to avoid the bronchoprotective effects of deep inhalation. This study compared different tidal breathing methacholine challenge methods; assessed the agreement between tidal dosimetric and continuous output challenges; and assessed challenge repeatability with different methods.

15 asthma patients performed dosimetric challenges and a continuous-output breath-actuated challenge, all ≥3 days apart. All subjects had a pre-bronchodilator forced expiratory volume in 1 s (FEV₁) ≥65% predicted, and a cumulative dose causing a 20% reduction in FEV₁ (PD₂₀) <1.2 mg.

Of the dosimetric challenges, one method increased methacholine concentration (standard dosimetric challenge), and one adjusted nebuliser output time to increase dose (adjusted dosimetric challenge). The adjusted dosimetric and continuous output challenges were performed twice on separate days to assess for repeatability. All challenges were matched for dose at each dose step. The mean PD₂₀ ratio of the standard dosimetric challenge to the adjusted dosimetric challenge was 0.90 (95% CI 0.66–1.23, p=0.49) and intraclass correlation coefficient (ICC) was 0.82. Repeated adjusted dosimetric challenges had an ICC 0.62 for PD₂₀. Repeated continuous output challenges had an ICC 0.74 for PD₂₀. The adjusted dosimetric and continuous output challenges correlated (r=0.69, p=0.0043; ICC 0.65), but PD₂₀ was higher for the adjusted dosimetric challenge (mean PD₂₀ ratio 2.31, 95% CI 1.57–3.40; p=0.0004).

Tidal dosimetric methacholine challenge using adjustment of nebuliser output produces results with good repeatability. The results of this adjusted dosimetric method differed from the continuous output method, underscoring that the results of different methacholine challenge methodologies may not be directly comparable.

Tidal breathing challenges are now the preferred method to administer a methacholine challenge. This study reports a tidal dosimetric methacholine challenge method that adjusts nebuliser output, which can be used to obtain results with good repeatability.https://bit.ly/3fX0F3f

Elevated Th17 cell frequencies and Th17/Treg ratio are associated with airway hyperresponsiveness in asthmatic children

Introduction: The elevation of T helper (Th)17 cell frequencies and the imbalance of Th17/regulatory T (Treg) cells occur in asthma pathogenesis. Airway hyperresponsiveness (AHR) is a cardinal feature of asthma, and Th17 responses can promote AHR. We hypothesized that changes in Th17 cells and the Th17/Treg ratio correlate with AHR in asthmatic children.Methods: Twenty asthmatic children and twenty healthy children were included in the study. The peak expiratory flow (PEF) % pred, forced expiratory volume in 1 s (FEV₁) % pred and the FEV₁/forced vital capacity (FVC) ratio were measured in all subjects. Methacholine challenge test (MCT) was performed in asthmatic children. Flow cytometric analysis was used to determine the proportions of Th17 and Treg cells in peripheral blood mononuclear cells. ELISA was used to assess serum levels of interleukin (IL)-17A and IL-10.Results: Th17 cell frequencies (2.272 ± 0.207% in asthmatics, 1.193 ± 0.131% in controls, P < 0.01) and Th17/Treg ratios (0.371 ± 0.0387 in asthmatics, 0.183 ± 0.020 in controls, P < 0.01) were significantly increased in asthmatic children compared to controls. In asthmatic children, the MCT grade had positive correlations with the Th17 cell frequencies [r = 0.718, P < 0.01], serum IL-17A level [r = 0.753, P < 0.01] and Th17/Treg ratio [r = 0.721, P < 0.01], while the log₁₀PD20-FEV₁ value was negatively correlated with the Th17 cell frequencies [r = -0.654, P < 0.01], serum IL-17A level [r = -0.652, P < 0.01] and Th17/Treg ratio [r = -0.625, P < 0.01].Conclusion: Th17 cell, IL-17A and Th17/Treg ratio were positively correlated with AHR in asthmatic children. It may be helpful to monitor Th17 cells and the Th17/Treg ratio as indicators of AHR in clinical practice.

Concurrence of elevated FeNO and airway hyperresponsiveness in nonasthmatic adolescents

OBJECTIVES

The aim of this study was to investigate airway responsiveness and eosinophil and neutrophil inflammatory markers in clinically confirmed nonasthmatic adolescents with elevated fractional exhaled nitric oxide (FeNO), a marker of type-2 inflammation in the airways.

METHODOLOGY

A total of 959 subjects from a general population, aged 12 to 15 years, answered a standardised questionnaire and underwent FeNO measurements at a screening visit at school. Adolescents without asthma, who had elevated FeNO (FeNO₁₀₀  > 15 ppb) (n = 19), and control subjects, with low FeNO (FeNO₁₀₀  < 5 ppb) and without reported symptoms of asthma or allergy (n = 28), participated in a follow-up study where FeNO₅₀ , airway responsiveness to methacholine (PD₂₀ ), blood eosinophil counts, and serum neutrophil lipocalin (HNL) and myeloperoxidase (MPO) levels were measured. Questionnaire follow-ups were performed 4 and 16 years later.

RESULTS

Airway responsiveness (PD₂₀ : 6.94 [1.87, 11.39] vs 11.42 [6.33, 59.4] µmol; P < .05) and blood eosinophil counts (0.31 [0.20, 0.44] vs 0.13 [0.1, 0.22] 10⁹ /L; P < .001) (geometric mean [95% CI]) were higher among cases than controls. A significant correlation between blood eosinophils and FeNO was found (rho = 0.41; P = .005). In contrast, serum HNL and MPO were lower in cases than controls (P < .05 both), and there was a negative correlation between HNL and FeNO (r = -0.31; P = .04). At both follow-ups, a higher proportion of subjects reported allergic symptoms compared with baseline (P = .02, P = .01).

CONCLUSIONS

Elevated FeNO in nonasthmatic adolescents was associated with airway hyperresponsiveness, elevated blood eosinophil counts, and lower systemic activation of neutrophils.

FEV1 recovery following methacholine challenge in asthma: Variability and comparison of methods

BACKGROUND

Methacholine challenges have been used in clinical trials to assess therapeutic effects and potential adverse reactions of interventions on pulmonary function in a sensitive population, such as in subjects with asthma. Here, we evaluate the variability of the methacholine challenge recovery model, and compare the results obtained for both incremental and bolus challenge methods.

METHODS

The extent, time course and variability of change in forced expiratory volume in 1 s (FEV₁) following repeated methacholine challenges in subjects with mild asthma were investigated in an open-label, four-period, fixed-sequence, two-method, replicate crossover study. At Visits 1 and 2, subjects underwent an incremental challenge using doubling doses of methacholine until a ≥20% decrease in FEV₁ was observed; at Visits 3 and 4, subjects underwent a bolus challenge, inhaling a single dose of methacholine calculated from the cumulative dose established during Visit 1.

RESULTS

A total of 19 subjects were included in the study. Both the mean FEV₁ area under the curve (FEV₁ AUC_0-tz) and mean maximum reductions in FEV₁ (absolute and relative) 120 min post-challenge values were higher for the incremental challenges than the bolus challenges, with no reported difference between repetitions of the same methodology. FEV₁ AUC_0-tz decrease 120 min post challenge demonstrated an intra-subject coefficient of variation (CV) of 47.2% (incremental) and 78.3% (bolus), suggesting considerable between-visit variability. The mean absolute, and similarly relative, maximum reductions in FEV₁ compared with post-diluent baseline values demonstrated lower intra-subject variability (incremental 21.16%, bolus 40.67%) than the FEV₁ AUC_0-tz-based endpoint. There was a trend towards faster recovery following the bolus challenge than with the incremental challenge. The provocative dose of methacholine inducing a ≥20% decrease in FEV₁ resulted in a between-group mean difference of 27.20% in the incremental challenge periods, with a high intra-subject CV of 80.64%, demonstrating considerable variability.

CONCLUSION

Maximum reduction in FEV₁ had the lowest variability. There was little difference between repetitions of the same methodology, as indicated by overlapping confidence intervals. There was a trend towards faster recovery following bolus challenge than with the incremental challenge. The results of this trial could be of value when designing future clinical trials using the methacholine challenge methodology.

Use of a vibrating mesh nebulizer for allergen challenge

Background

Allergen inhalation tests are a valuable research tool. The allergen dose producing an early asthmatic response (EAR) can be predicted from methacholine responsiveness and allergen skin test endpoint (STE). The Wright^® jet nebulizer, which is both inefficient and increasingly difficult to obtain, has been used historically. We assessed the Solo^® vibrating mesh nebulizer as an alternative for allergen and methacholine challenges.

Methods

Eighteen mild atopic asthmatics completed the study. Doubling concentration allergen prick skin tests were performed to determine the STE in allergen units/mL. The Wright^® protocol was used to measure the methacholine provocation dose causing a 20% forced expired volume in one second (FEV₁) fall (PD₂₀) (μg) and the allergen PD₂₀ (units). The Solo^® protocol (0.5 mL nebulized to completion, tidal breathing inhalation) was used to determine both methacholine PD₂₀ and allergen PD₂₀. The nebulizer order was randomized and separated by ≥ 2 weeks.

Results

All data were log transformed. The allergen PD₂₀, predicted from the methacholine PD₂₀ and the STE, was within 2 doubling doses of the PD₂₀ measured with the Wright^® and 2.64 doubling doses of that measured with Solo^®. The Wright^® allergen PD₂₀ correlated with the Wright^® methacholine PD₂₀ (r = 0.74) and the STE (r = 0.78) and more strongly with the product of the two (Wright^® methacholine PD₂₀ × STE, r = 0.91, p < 0.00001). The Solo^® allergen PD₂₀ showed similar relationships with the Solo^® methacholine PD₂₀ (r = 0.61), the STE (r = 0.75) and the product of the two (Solo^® methacholine PD₂₀ × STE, r = 0.83, p < 0.00002). The Wright^® and the Solo^® methacholine geometric mean PD₂₀s were not significantly different (49.3 and 54.5 μg respectively, p = 0.62). The Wright^® allergen PD₂₀ was slightly but significantly lower than the Solo^® allergen PD₂₀ (geometric means 6.7 and 10.5 units respectively, p = 0.003).

Conclusion

The Solo^® allergen PD₂₀ showed the same relationship with methacholine responsiveness and STE as did the Wright^®. The Solo^® allergen PD₂₀ was slightly but significantly higher than the Wright^® allergen PD₂₀. The Solo^® vibrating mesh nebulizer was well tolerated and is an acceptable alternative for allergen challenge.

Trial registration clinicaltrials.gov: NCT03491358

Bronchial hyper-responsiveness: a technical update

Background

Bronchial hyper-responsiveness (BHR) is often regarded as a 'hallmark' of asthma, and bronchoprovocation testing is frequently performed to support a diagnosis of asthma. The European Respiratory Society (ERS) and American Thoracic Society (ATS) have recently updated their technical standards and guidelines for performing methacholine challenge testing (MCT), the most commonly performed clinical test of BHR.

Aims

To review the updated guidelines and discuss the various changes and their potential impact on clinicians.

Methods

We performed a systematic review of references identified using Medline and hand searches of identified articles.

Results

The new ERS and ATS guidelines recommend that MCT be performed using tidal breathing, not deep inspirations with breath holding, that results be reported as the PD20 (cumulative dose causing a 20% fall in forced expiratory volume in 1 s [FEV1]), rather than PC20 (concentration causing a 20% fall in FEV1), and that manufacturers of nebulizers and other delivery systems provide performance characteristics to allow calculation of PD20 values. Our preliminary survey found that the new guidelines are only slowly being adopted.

Conclusions

Clinicians should be aware that recommended BHR testing methods, particularly for MCT, have changed. As a result, they should anticipate that test outcomes will increasingly be reported in terms of PD20, which will facilitate longitudinal assessment of their patients. Compliance with the new guidelines will increase the sensitivity of MCT in mild and asymptomatic asthmatics.

A Dose-Response Study Examining the Use of Methacholine Challenge to Demonstrate Local Therapeutic Equivalence of the Salmeterol Component of Generic Inhaled Fluticasone Propionate/Salmeterol Combination Products

Background: Asthma is widely treated using inhaled corticosteroid/long-acting beta agonist (LABA) combinations, for example, fluticasone propionate/salmeterol (FPS) dry powder inhaler, marketed as Advair^® Diskus^®. Some regulators require generics to demonstrate local (lung) therapeutic equivalence (LTE) for each component of the FPS reference, ideally with a dose-response within the approved FPS dose range. We sought to develop a methacholine challenge (MeCh) LTE methodology for assessing the LABA (salmeterol) component of FPS. Methods: Forty-six patients with asthma received single doses of albuterol (active control; 90 or 180 μg), FPS (100/50 or 200/100 μg), and placebo on 5 separate study days. Spirometry and MeCh were performed 1, 6, and 10 hours after study drug inhalation. Primary endpoint was provocative concentration of methacholine producing a 20% fall in forced expiratory volume in 1 second (PC₂₀). Study entry required screening PC₂₀ ≤8 mg/mL, with a greater than fourfold increase (and PC₂₀ ≤128 mg/mL) after 180 μg albuterol. Results: Both albuterol (90 and 180 μg) and FPS (100/50 and 200/100 μg) significantly increased PC₂₀ compared with placebo (sustained 6 and 10 hours postdose with FPS but not albuterol). The dose-response slopes (95% confidence interval) estimated 1 hour after treatment were 0.374 (-0.068 to 0.815) and 0.310 (-0.135 to 0.754) between low and high doses of albuterol and FPS, respectively, both nonsignificant. Slopes were shallower than those available in the literature for albuterol and formoterol, but similar to those for salmeterol. Conclusions: These data confirm that the bronchoprotective effect of FPS lasts longer than that of albuterol. The shallow dose-response slope we observed for albuterol is contrary to previous reports, probably due to the measurement of PC₂₀ beginning at 1 hour postdose. The results suggest that use of MeCh to assess LTE for salmeterol formulations may be more difficult to accomplish than it is for albuterol and formoterol products.

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.

Recent advances in aerosolised drug delivery

Pulmonary route is extensively studied for the diagnosis and treatment of pulmonary and extra pulmonary disease conditions such as asthma, tuberculosis, emphysema, and bronchitis. Formulation design, inhalation device and particle size play key role in determining the aerosol performance. The lack of desired clinical outcome along with the problem regarding efficacy or any adverse drug effect may arise due to improper training and education in use of the device to control the actuation and aerosol inhalation. This review summarizes the difference in the mechanistic features of current marketed aerosol delivery devices with respect to mechanism of aerosol generation with possible advancements in the aerosol design. The delivery options in the pulmonary route and its merits together with the limitations are also discussed. An update is provided regarding the current research and clinical outcome of the use of inhalational technology.

Club Cell Secretory Protein Deficiency Leads to Altered Lung Function

RATIONALE

CC16 (club cell secretory protein-16), a member of the secretoglobin family, is one of the most abundant proteins in normal airway secretions and has been described as a serum biomarker for obstructive lung diseases.

OBJECTIVES

To determine whether low CC16 is a marker for airway pathology or is implicated in the pathophysiology of progressive airway damage in these conditions.

METHODS

Using human data from the birth cohort of the Tucson Children's Respiratory Study, we examined the relation of circulating CC16 levels with pulmonary function and responses to bronchial methacholine challenge from childhood up to age 32 years. In wild-type and CC16-/- mice, we set out to comprehensively examine pulmonary physiology, inflammation, and remodeling in the naive airway.

MEASUREMENTS AND MAIN RESULTS

We observed that Tucson Children's Respiratory Study participants in the lowest tertile of serum CC16 had significant deficits in their lung function and enhanced airway hyperresponsiveness to methacholine challenge from 11 years throughout young adult life. Similarly, CC16-/- mice had significant deficits in lung function and enhanced airway hyperresponsiveness to methacholine as compared with wild-type mice, which were independent of inflammation and mucin production. As compared with wild-type mice, CC16-/- mice had significantly elevated gene expression of procollagen type I, procollagen type III, and α-smooth muscle actin, areas of pronounced collagen deposition and significantly enhanced smooth muscle thickness.

CONCLUSIONS

Our findings support clinical observations by providing evidence that lack of CC16 in the lung results in dramatically altered pulmonary function and structural alterations consistent with enhanced remodeling.

Direct bronchoprovocation test methods: history 1945-2018

INTRODUCTION

Bronchoprovocation inhalation challenge tests with direct acting stimuli (e.g. methacholine) are widely used clinically to aid in the diagnosis of asthma. Areas covered: The history of direct challenges with histamine and muscarinic agonists is reviewed. This began with parenteral administration of stimuli with responses monitored clinically and by VC, progressing to inhalation dose-response challenges monitored by FEV₁ and FEV₁/VC ratio, both (the challenge method and the technology to measure FEV₁) developed by Robert Tiffeneau in the mid-1940s. Careful standardization of methods has become appreciated albeit after-the-fact. Recent guidelines recommend standardizing the methacholine PD₂₀ at 400 μg above which a methacholine challenge is considered negative.

CONCLUSIONS

The methacholine inhalation test is highly sensitive for a diagnosis of current asthma when symptoms under evaluation are clinically current and when methacholine is inhaled without deep inhalations. Under these circumstances, a methacholine PD₂₀ > 400 μg excludes current asthma with reasonable certainty. PD₂₀ values >25 μg and ≤400 μg will have a variable specificity and positive predictive value for asthma which increases the lower the PD₂₀ and the higher the pre-test probability for a diagnosis of asthma. A PD₂₀ ≤25 μg has high specificity and low sensitivity for asthma.

Dose omission to shorten methacholine challenge testing: clinical consequences of the use of a 10% fall in FEV1 threshold

Introduction

In methacholine challenge testing (MCT), skipping a methacholine dose is suggested if FEV₁ falls by < 5%. Using a larger threshold may further shorten test duration, but data supporting this hypothesis is lacking. We evaluated the safety and consequences of using a 10% FEV₁ fall as threshold to skip the next dose of methacholine in patients undergoing MCT.

Methods

We reviewed MCTs performed in our center in 2017–2018. A ≤ 10% FEV₁ fall allowed the omission of the next methacholine dose. Patients of interest were those in which a dose was skipped after a previous FEV₁ fall outside the usual range (5–10%, termed “skip_5–10%”). Adverse events [AE; mild: > 1 nebulized salbutamol dose (2.5 mg) to reach basal FEV₁, palpitations; severe: hypoxemia and/or need for medical attention or intervention] were compared in the skip_5–10% group and others. Regression analysis was used to identify predictors of AE.

Results

208 MCTs were analysed (135 males, age 52 ± 15 years). Skip_5–10% occurred 111 times in 90 tests. Prevalence of AE was 5% and all were mild. Patients who developed AEs had lower FEV₁, FVC and FEV₁/FVC ratio, and higher lung volume values (all p < 0.05), but similar prevalence of skip_5–10% (36 vs. 44%, p = 0.64). Overall, MCTs in which at least one skip_5–10% occurred had a lower mean number of doses (3.1 ± 0.6 vs. 3.5 ± 1.3 doses, p = 0.007). Baseline residual volume was independently related to the development of AEs (OR 1.05, 95% CI 1.01–1.10, p = 0.01), but not the presence of a skip_5–10%, even when the skipped dose directly led to the reaching of PC₂₀ (OR 5.40, 95% CI 0.73–39.22, p = 0.10).

Conclusion

Omitting a methacholine dose based on a ≤ 10% fall in FEV₁ occurs frequently and has the potential to shorten test duration. AE are rare, but patients with worse baseline lung function and gas trapping are at increased risk of mild side effects.

Alternaria sensitisation at age 6 years is associated with subsequent airway hyper-responsiveness in non-asthmatics

In the non-selected birth cohort Tucson Children's Respiratory Study, early sensitisation to Alternaria was associated with increased airway hyper-responsiveness (AHR) into adult life among non-asthmatics. The increase in AHR was of a similar magnitude to that seen for Alternaria sensitised asthmatics and was primarily evident among those who were overweight or obese. In contrast, there was no significant association between early sensitisation to aeroallergens other than Alternaria and AHR among non-asthmatics. Why this group of Alternaria sensitised individuals without asthma demonstrated increased AHR of a magnitude similar to asthmatics is unknown and requires further investigation.

Methacholine challenge test: Comparison of tidal breathing and dosimeter methods in children

INTRODUCTION

Methacholine Challenge Test (MCT) is used to confirm, assess the severity and/or rule out asthma. Two MCT methods are described as equivalent by the American Thoracic Society (ATS), the tidal breathing and the dosimeter methods. However, the majority of adult studies suggest that individuals with asthma do not react at the same PC₂₀ between the two methods. Additionally, the nebulizers used are no longer available and studies suggest current nebulizers are not equivalent to these. Our study investigates the difference in positive MCT tests between three methods in a pediatric population.

METHODS

A retrospective, chart review of all MCT performed with spirometry at the Montreal Children's Hospital from January 2006 to March 2016. A comparison of the percentage positive MCT tests with three methods, tidal breathing, APS dosimeter and dose adjusted DA-dosimeter, was performed at different cutoff points up to 8 mg/mL.

RESULTS

A total of 747 subjects performed the tidal breathing method, 920 subjects the APS dosimeter method, and 200 subjects the DA-dosimeter method. At a PC₂₀ cutoff ≤4 mg/mL, the percentage positive MCT was significantly higher using the tidal breathing method (76.3%) compared to the APS dosimeter (45.1%) and DA-dosimeter (65%) methods (P < 0.0001).

CONCLUSION

The choice of nebulizer and technique significantly impacts the rate of positivity when using MCT to diagnose and assess asthma. Lack of direct comparison of techniques within the same individuals and clinical assessment should be addressed in future studies to standardize MCT methodology in children.

Standardizing dose in dosimetric bronchial challenge tests

Recent technical recommendations on bronchial challenge testing aim at standardized assessment of provocative dose of causing 20% decrease in FEV1 (PD20). The aim of this study was to investigate the effect of mode of nebulization on the output of a computerized dosimeter (APS) and to compare PD20 obtained by two different dosimetric systems in vivo. The output of the APS system was tested during continuous nebulization, and using simulated breaths, for intermittent actuations with four different durations. Using output data, a modified methacholine challenge protocol was applied for APS and compared with a standard set-up using Spira dosimeter in 14 asthmatic patients attending duplicate methacholine challenges using both systems, within median (range) 3 (1-6) days apart. The calculated output (mg min^-1 ) with all the intermittent mode settings was significantly higher (P<0·001) than in the continuous mode, and in the intermittent mode, the output was dependent of the pulse duration. The PD20 values assessed with the APS and Spira systems were significantly correlated (r = 0·69; P<0·007), without systematic difference in the geometric means (P = 0·10). A moderate to good agreement was found for assessment of significant hyperresponsiveness. The results suggest that in dosimetric systems for bronchial challenge tests, the output of the nebulizer is dependent on the mode of nebulization, and this should be considered when standardizing the dose between devices and protocols. As long as the delivered dose is determined for the specified nebulization mode of the protocol, it may be possible to obtain comparable results between different devices.

Realising the potential of various inhaled airway challenge agents through improved delivery to the lungs

Inhaled airway challenges provoke bronchoconstriction in susceptible subjects and are a pivotal tool in the diagnosis and monitoring of obstructive lung diseases, both in the clinic and in the development of new respiratory medicines. This article reviews the main challenge agents that are in use today (methacholine, mannitol, adenosine, allergens, endotoxin) and emphasises the importance of controlling how these agents are administered. There is a danger that the optimal value of these challenge agents may not be realised due to suboptimal inhaled delivery; thus considerations for effective and reproducible challenge delivery are provided. This article seeks to increase awareness of the importance of precise delivery of inhaled agents used to challenge the airways for diagnosis and research, and is intended as a stepping stone towards much-needed standardisation and harmonisation in the administration of inhaled airway challenge agents.

Methacholine Challenge Testing: A Novel Method for Measuring PD20

BACKGROUND

New guidelines for methacholine challenge testing recommend reporting the test outcome as dose rather than concentration. Jet nebulizers have historically been used for methacholine challenge testing, but much of the weight loss, often (incorrectly) referred to as aerosol output, is actually evaporation. The Wright nebulizer is well characterized and still widely used, but its availability is unclear, and it is nondisposable. We developed a novel method using a vibrating mesh nebulizer (Solo). This method was compared with the standard 2-min tidal breathing method using the Wright nebulizer. Repeatability within and between nebulizers was also tested.

METHODS

Fifteen patients with mild asthma completed four methacholine challenges (two with the Solo vibrating mesh nebulizer and two with the Wright jet nebulizer). Challenges with the same nebulizer were 24 h apart, and challenges between nebulizers were separated by 1 week. Standard 2-min tidal breathing methods were used with the Wright nebulizer. For the Solo nebulizer, the tidal breathing method was modified by nebulizing to completion 0.5 mL of doubling concentrations of methacholine at 5-min intervals.

RESULTS

Geometric mean methacholine doses required to cause a 20% fall in FEV₁ were similar (96 vs 110 μg; P > .05); methacholine concentrations that caused a 20% fall in FEV₁ were significantly lower with the vibrating mesh nebulizer (0.48 vs 4.4 mg/mL; P < .001). Repeatability of methacholine doses required to cause a 20% fall in FEV₁ within and between nebulizers was excellent (intraclass correlation coefficient > 0.92).

CONCLUSIONS

We have developed a novel, simple, repeatable method for conducting methacholine challenges using new nebulizer technology. Importantly, the method meets recommendations set out in the new guidelines.

TRIAL REGISTRY

ClinicalTrials.gov; No.: 02965482; URL: www.clinicaltrials.gov.

Methacholine Challenge: Comparison of Airway Responsiveness Produced by a Vibrating Mesh Nebulizer Versus a Jet Nebulizer

BACKGROUND

The latest methacholine challenge testing (MCT) guidelines published by the European Respiratory Society recommend the characterization of nebulizers before their use in clinics and research. Such investigations are necessary for accurately determining the provocative dose of methacholine causing a 20% fall in FEV₁ (PD₂₀) delivered by a given device. The standard English Wright (Wright) jet nebulizer recommended in the 1999 guidelines by the American Thoracic Society has become difficult to obtain and possesses some characteristics that complicate the calculation of dose delivery from this device (e.g. evaporation). Our objective was to determine if the Aerogen^® Solo (Solo) vibrating mesh nebulizer provides similar methacholine challenge test results compared to the currently used Wright jet nebulizer.

METHODS

Sixty mild-to-moderate asthmatics were studied across three research sites in a randomized crossover study. Both methacholine challenges were completed at least 24 hours apart within a 2-week period. Testing with the Wright device was performed as per the 2-minute tidal breathing protocol. The Solo study arm followed the same procedure except for a shorter inhalation time of 1 minute. The provocative concentration of methacholine causing a 20% fall in FEV₁ (PC₂₀) and the methacholine PD₂₀ were calculated following each methacholine challenge.

RESULTS

The geometric mean methacholine PC₂₀ values for the Solo and the Wright differed statistically (0.65 mg/mL vs. 2.58 mg/mL, respectively, p < 0.00001) and clinically. Between-nebulizer geometric mean methacholine PD₂₀ results are comparable by clinical standards [81.7 μg (Solo) vs. 64.7 μg (Wright)], although the slight difference in dose was statistically significant (p = 0.018).

CONCLUSIONS

The comparability of PD₂₀ values between the Solo and the Wright validates the importance of reporting airway responsiveness to methacholine in terms of dose and not concentration, as stressed in the latest testing guidelines. This finding along with several benefits associated with the Solo make it a promising nebulizer for performing MCT.

The effect of glycopyrronium and indacaterol, as monotherapy and in combination, on the methacholine dose-response curve of mild asthmatics: a randomized three-way crossover study

BACKGROUND

Methacholine dose-response curves illustrate pharmacologic bronchoprotection against methacholine-induced airway hyperresponsiveness and can be used to quantitate changes in airway sensitivity (position), reactivity (slope), and maximal responsiveness following drug administration. Our objective was to determine the influence of single-dose glycopyrronium (long-acting muscarinic antagonist) and indacaterol (ultra-long acting β₂ agonist), as monotherapy and in combination, on the methacholine dose-response curve of mild asthmatics and to compare these findings with a non-asthmatic control curve.

METHODS

This was a randomized, double blind, double dummy, three-way crossover study. For asthmatic participants (n = 14), each treatment arm included a baseline methacholine challenge, drug administration, and repeat methacholine challenges at 1, 24, and 48 h. Non-asthmatic control participants (n = 15) underwent a single methacholine challenge and did not receive any study treatment. Methacholine dose-response curves were graphed as the percent fall in forced expiratory volume in 1 s (FEV₁) for each methacholine concentration administered. Best-fit curves were then generated. Differences in airway reactivity were calculated through linear regression. Changes in airway sensitivity were assessed as the shift in the provocative concentration of methacholine causing a 20% fall in FEV₁.

RESULTS

Compared to baseline, all treatments significantly reduced airway sensitivity to methacholine at 1 h post-dose (indacaterol ~1.5 doubling concentrations; glycopyrronium ~5 doubling concentrations; combination ~5 doubling concentrations). Bronchoprotection at 24 and 48 h remained significant with glycopyrronium and combination therapy only. Airway reactivity was not influenced by indacaterol whereas glycopyrronium significantly reduced airway reactivity at all time-points (p = 0.003-0.027). The combination significantly decreased slope at 1 (p = 0.021) and 24 (p = 0.039) hours only. The non-asthmatic control and 1-h glycopyrronium curves are nearly identical. Only the non-asthmatic control and 1-h post-combination therapy curves appeared to generate a true response plateau (three data points within 5%), which occurred at a 14% fall in FEV₁.

CONCLUSIONS

Methacholine dose-response curves differentiate the bronchoprotective mechanisms triggered by different classes of asthma medications. Assessment of bronchoprotection using methacholine dose-response curves may be useful during clinical development of respiratory medications when performing superiority, equivalence, or non-inferiority trials.

TRIAL REGISTRATION

clinicaltrials.gov ( NCT02953041 ). Retrospectively registered on October 24th 2016.

ERS technical standard on bronchial challenge testing: general considerations and performance of methacholine challenge tests

This international task force report updates general considerations for bronchial challenge testing and the performance of the methacholine challenge test. There are notable changes from prior recommendations in order to accommodate newer delivery devices. Rather than basing the test result upon a methacholine concentration (provocative concentration (PC20) causing a 20% fall in forced expiratory volume in 1 s (FEV1)), the new recommendations base the result upon the delivered dose of methacholine causing a 20% fall in FEV1 (provocative dose (PD20)). This end-point allows comparable results from different devices or protocols, thus any suitable nebuliser or dosimeter may be used, so long as the delivery characteristics are known. Inhalation may be by tidal breathing using a breath-actuated or continuous nebuliser for 1 min (or more), or by a dosimeter with a suitable breath count. Tests requiring maximal inhalations to total lung capacity are not recommended because the bronchoprotective effect of a deep breath reduces the sensitivity of the test.

Airway Hyperresponsiveness in Asthma: Measurement and Clinical Relevance

Airway hyperresponsiveness is a characteristic feature of asthma, and its measurement is an important tool in its diagnosis. With a few caveats, methacholine bronchial provocation by a 2-minute tidal breathing method is highly sensitive; a negative test result (PC₂₀ > 16 mg/mL, PD₂₀ > 400 μg) rules out current asthma with reasonable certainty. A PC₂₀ value of less than 1 mg/mL/PD₂₀ value of less than 25 μg is highly specific (ie, diagnostic) but quite insensitive for asthma. For accurate interpretation of the test results, it is important to control and standardize technical factors that have an impact on nebulizer performance. In addition to its utility to relate symptoms such as cough, wheeze, and shortness of breath to variable airflow obstruction (ie, to diagnose current asthma), the test is useful to make a number of other clinical assessments. These include (1) evaluation of patients with occupational asthma, (2) evaluation of patients with exercise-induced respiratory symptoms, (3) evaluation of novel asthma medications, (4) evaluation of relative potency of inhaled bronchodilators, (5) as a biomarker to adjust anti-inflammatory therapy to improve clinical outcomes, and (6) in the evaluation of patients with severe asthma to rule out masqueraders such as laryngeal dysfunction. The actual mechanism of altered smooth muscle behavior in asthma that is assessed by direct (eg, methacholine) or indirect (eg, allergen) bronchial provocation remains one of the most fundamental questions related to asthma that needs to be determined. The test is underutilized in clinical practice.

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.

Bronchial hyperresponsiveness

BACKGROUND

Bronchial hyperresponsiveness (BHR) is often regarded as a 'hallmark' of asthma and bronchoprovocation testing is frequently performed to support a diagnosis of asthma. However, BHR is also found in a spectrum of other lung diseases and can be provoked by a variety of specific stimuli.

AIMS

To review the pathophysiology of BHR, discuss various methods of testing for BHR and describe the epidemiology of BHR in a variety of previously studied populations.

METHODS

We performed a systematic review of references identified using Medline and hand searches of identified articles. Because of space limitations, we have included those reports that seem most representative of the overall BHR literature.

RESULTS

BHR can be induced by a variety of stimuli that trigger a number of different but overlapping physiological mechanisms. Bronchoprovocation testing can be performed using a variety of stimuli, various protocols and differing test criteria, yielding results that may be discordant. Elevated rates of BHR have been reported in studies of smokers, chronic obstructive pulmonary disease patients, atopics, athletes, exposed workers and the general population.

CONCLUSIONS

Due to the prevalence of BHR in a spectrum of clinical patients and working populations, clinicians should be aware that BHR is not specific for asthma. When performed correctly, the greatest clinical value of BHR testing is to rule out suspected asthma in patients in whom testing is negative. Assessment of BHR also provides insights into the pathological mechanisms of airway disease.