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

Trend of Bronchial Hyperresponsiveness to Methacholine as a Cost Predictor of Mild-to-Moderate Asthma: A Twelve-Month Survey in Teenagers

Bronchial asthma is characterized by variable airflow obstruction, airway inflammation, and bronchial hyperresponsiveness (BHR) to non-specific stimuli. The role of underlying airway inflammation and of related long-lasting BHR has been suboptimally investigated in teenagers with mild-to-moderate asthma, as has the corresponding economic impact over time. The aim of the present study was to calculate the cost of mild-to-moderate atopic asthma in teenagers arising from their degree of persisting BHR over a twelve-month period.

METHODS

Patients aged 12-18 years with mild-to-moderate symptoms treated with fluticasone fumarate/vilanterol 92/22 mcg daily were retrospectively followed for 12 months. Usual spirometric parameters, BHR to methacholine (MCh), and resource consumption (visits, hospitalizations, systemic steroids and/or antibiotics courses, school days off) were assessed at recruitment (the index date) and after 6 and 12 months. Adherence to treatment was also calculated. The cost of asthma was calculated based on Italian tariffs and published papers. The trend over time in BHR and the association between response to MCh and total cost were investigated by using regression models adjusted for repeated measures.

RESULTS

106 teenagers (53 males, age 15.9 ± 1.6 years) were investigated. The annual cost of asthma proved significantly related to the BHR trend: every increment of a factor 10 in the response to MCh was associated with a saving of EUR 184.90 (95% CI -305.89 to -63.90). BHR was progressively optimized after 6 and 12 months in relation to the patients' compliance to treatment (≥70% of prescribed inhalation doses).

CONCLUSIONS

the usual spirometric parameters are largely insufficient to reflect the effects of underlying persistent inflammation in milder forms of asthma in teenagers. In terms of clinical governance, the periodic assessment of non-specific BHR is the appropriate procedure from this point of view. Non-specific BHR proves a reliable procedure for predicting and monitoring the economic impact of mild-to-moderate asthma in teenagers over time.

Polypharmacy Interactions Impacting Methacholine Challenge Testing for Asthma Assessment in Older People

Objective To investigate potential reasons for unusually high incidence of negative Methacholine Challenge Tests (MCT), following standardized MCT medication-hold protocol, in older people with physician-diagnosed asthma. Design An analysis of a longitudinal observational parent study of asthma. Setting Community-dwelling participants were evaluated in an outpatient clinic and at home. Participants Screening inclusion criteria for the parent study included 60 years of age or older, physician diagnosis of asthma, and a positive response to at least one of six asthma screening questions. Participants were enrolled in the study if they also demonstrate either: (1) a postbronchodilator administration response showing an increase of at least 12% and 200 mL in forced expiratory volume or an increase of at least 12% and 200 mL in forced vital capacity, or (2) an MCT result of PC20 ≤ 16 mg/mL (indicating bronchial hyper-responsiveness, MCT positive). Exclusion criteria included diagnosis of cognitive impairment or dementia, residing in a long-term care facility, more than 20 pack/ year smoking history or a history of smoking within the previous five years, inability to perform pulmonary function testing maneuvers, and a Prognostic Index score of greater than 10. Interventions Analysis of participant data for non-medication- and medication-exposure factors for association with negative MCT results. Results Anticholinergic burden and statin use were positively associated with negative MCT. Conclusion Medications not accounted for in medication-hold protocols, and concurrently in use, may impact clinical tests and outcomes.

Validation of the clinical utility of sGaw as a response variable in methacholine challenge testing

BACKGROUND AND OBJECTIVE

Airway hyperresponsiveness (AHR) is commonly assessed by a methacholine challenge test (MCT), during which a provocative concentration causing a 20% reduction in forced expiratory volume in 1 second (FEV₁ ) (PC₂₀ ) < 8 mg/ml is considered a positive response. However, a fall in specific airway conductance (sGaw) may also have clinical significance. The purpose of this study was to assess whether AHR determined by a provocative concentration causing a 40% reduction in sGaw (PC₄₀ ) < 8 mg/ml corresponds to a clinical diagnosis of asthma.

METHODS

We analysed the changes in spirometry, lung volumes and sGaw during MCT in 211 randomly selected patients being evaluated for AHR to support a clinical diagnosis of asthma.

RESULTS

The mean (SD) age of the group was 53 (15) years, with 141 women (67%). Overall lung function was normal, with FEV₁  = 92 (15) % predicted, total lung capacity = 97 (13) % predicted and sGaw = 0.19 (0.15-0.23) L/s/cm H₂ O/L, (median, 25-75 IQR). There were many more patients who responded by PC₄₀ only (n = 120) than who responded by PC₂₀ (n = 52). There was no significant difference in asthma diagnosis between the PC₂₀ (98%) and PC₄₀ (93%) groups, and we estimate 34% of patients with a diagnosis of asthma would have been classified as having no AHR if only the FEV₁ criterion was used.

CONCLUSION

Changes in sGaw during MCT indicate clinically significant AHR in support of a clinical diagnosis of asthma among patients being evaluated for asthma.

Characterization of Persistent Uncontrolled Asthma Symptoms in Community Members Exposed to World Trade Center Dust and Fumes

The destruction of the World Trade Center (WTC) towers on the 11th of September, 2001 released a vast amount of aerosolized dust and smoke resulting in acute and chronic exposures to community members as well as responders. The WTC Environmental Health Center (WTC EHC) is a surveillance and treatment program for a diverse population of community members, including local residents and local workers with WTC dust exposure. Many of these patients have reported persistent lower respiratory symptoms (LRS) despite treatment for presumed asthma. Our goal was to identify conditions associated with persistent uncontrolled LRS despite standard asthma management. We recruited 60 patients who were uncontrolled at enrollment and, after a three-month run-in period on high-dose inhaled corticosteroid and long acting bronchodilator, reassessed their status as Uncontrolled or Controlled based on a score from the Asthma Control Test (ACT). Despite this treatment, only 11 participants (18%) gained Controlled status as defined by the ACT. We compared conditions associated with Uncontrolled and Controlled status. Those with Uncontrolled symptoms had higher rates of upper airway symptoms. Many patients had persistent bronchial hyper-reactivity (BHR) and upper airway hyper-reactivity as measured by paradoxical vocal fold movement (PVFM). We found a significant increasing trend in the percentage of Controlled with respect to the presence of BHR and PVFM. We were unable to identify significant differences in lung function or inflammatory markers in this small group. Our findings suggest persistent upper and lower airway hyper-reactivity that may respond to standard asthma treatment, whereas others with persistent LRS necessitate additional diagnostic evaluation, including a focus on the upper airway.

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.

Older age and obesity are associated with increased airway closure in response to methacholine in patients with asthma

BACKGROUND AND OBJECTIVE

The reduction of forced expiratory volume in 1 s (FEV₁ ) in response to methacholine challenge in asthma may reflect two components: airway narrowing, assessed by the change in FEV₁ /forced vital capacity (FVC), and airway closure, assessed by the change in FVC. The purpose of this study was to determine the degree and determinants of airway closure in response to methacholine in a large group of asthmatic patients participating in studies conducted by the American Lung Association-Airways Clinical Research Centers (ALA-ACRC).

METHODS

We used the methacholine challenge data from participants in five studies of the ALA-ACRC to determine the closing index, defined as the contribution of airway closure to the decrease in FEV₁ , and calculated as %ΔFVC/%ΔFEV₁ .

RESULTS

There were a total of 936 participants with asthma, among whom the median closing index was 0.67 relative to that of a published healthy population of 0.54. A higher closing index was associated with increased age (10-year increments) (0.04, 95% CI = 0.02, 0.05, P < 0.005) and obesity (0.07, 95% CI = 0.03, 0.10, P < 0.001). There was no association between the closing index and asthma control.

CONCLUSION

Our findings confirm that airway closure in response to methacholine occurs in a large, diverse population of asthmatic participants, and that increased airway closure is associated with older age and obesity. These findings suggest that therapies targeting airway closure may be important in patients with a high closing index.

Systematic Approach to Asthma of Varying Severity

Asthma is a serious global health issue and asthma guidelines recommend a stepwise approach to management with goals to achieve control and minimize future risk. Prior to escalation of pharmacotherapy, steps to confirm accurate diagnosis as well as address comorbidities and triggers are critical to effective asthma management. This article provides readers with a structured approach to evaluation and management of asthma of varying severity.

[Guidelines for methacholine provocation testing]

Bronchial challenge with the direct bronchoconstrictor agent methacholine is commonly used for the diagnosis of asthma. The "Lung Function" thematic group of the French Pulmonology Society (SPLF) elaborated a series of guidelines for the performance and the interpretation of methacholine challenge testing, based on French clinical guideline methodology. Specifically, guidelines are provided with regard to the choice of judgment criteria, the management of deep inspirations, and the role of methacholine bronchial challenge in the care of asthma, exercise-induced asthma, and professional asthma.

Effect of Continuous Positive Airway Pressure on Airway Reactivity in Asthma. A Randomized, Sham-controlled Clinical Trial

RATIONALE

Studies have demonstrated that application of stress suppresses airway smooth muscle contractility. In animal models of asthma, continuous positive airway pressure (CPAP) reduced airway reactivity. Short-term studies of CPAP in patients with asthma showed reductions in airway reactivity.

OBJECTIVES

To evaluate whether nocturnal CPAP decreased the provocative concentration of methacholine to reduce FEV₁ by 20% (PC₂₀).

METHODS

One hundred ninety-four individuals with asthma were randomized (1:1:1) to use CPAP with warmed, filtered, humidified air at night at pressures either less than 1 cm H₂O (sham) or at 5 cm H₂O or 10 cm H₂O. The primary outcome was change in PC₂₀ after 12 weeks.

MEASUREMENTS AND MAIN RESULTS

Adherence to CPAP was low in all groups. Regardless, all groups had a significant improvement in PC₂₀, with 12 weeks/baseline PC₂₀ ratios of 2.12, 1.73, and 1.78 for the sham, 5 cm H₂O, and 10 cm H₂O groups, respectively, and no significant differences between the active and sham groups. Changes in FEV₁ and exhaled nitric oxide were minimal in all groups. The sham group had larger improvements in most patient-reported outcomes measuring asthma symptoms and quality of life, as well as sinus symptoms, than the 5 cm H₂O group. The 10 cm H₂O group showed similar but less consistent improvements in scores, which were not different from improvements in the sham group.

CONCLUSIONS

Adherence to nocturnal CPAP was low. There was no evidence to support positive pressure as being effective for reducing airway reactivity in people with well-controlled asthma. Regardless, airway reactivity was improved in all groups, which may represent an effect of participating in a study and/or an effect of warm, humid, filtered air on airway reactivity. Clinical trial registered with www.clinicaltrials.gov (NCT01629823).

Bronchial Reactivity and Lung Function After World Trade Center Exposure

BACKGROUND

World Trade Center (WTC)-exposed rescue/recovery workers endured massive respiratory insult from inhalation of particulate matter and gases, resulting in respiratory symptoms, loss of lung function, and, for many, bronchial hyperreactivity (BHR). The persistence of respiratory symptoms and lung function abnormalities has been well-documented, whereas persistence of BHR has not been investigated.

METHODS

A total of 173 WTC-exposed firefighters with bronchial reactivity measured within 2 years after September 11, 2001 (9/11) (baseline methacholine challenge test), were reevaluated in 2013 and 2014 (follow-up methacholine challenge test). FEV1 measurements were obtained from the late pre-9/11, early post-9/11, and late post-9/11 periods. Respiratory symptoms and corticosteroid treatment were recorded.

RESULTS

Bronchial reactivity remained stable (within 1 doubling dilution) for most (n = 101, 58%). Sixteen of 28 (57%) with BHR (provocative concentration of methacholine producing a 20% decline in FEV1 <8 mg/mL) at baseline had BHR at follow-up, and an additional 27 of the 145 (19%) without BHR at baseline had BHR at follow-up. In multivariable models, we found that BHR baseline was strongly associated with BHR follow-up (OR, 6.46) and that BHR at follow-up was associated with an estimated 15.4 mL/y greater FEV1 decline than experienced by those without BHR at follow-up. Annual FEV1 decline was moderated by corticosteroid use.

CONCLUSIONS

Persistent BHR and its deleterious influence on lung function suggest a role for airway inflammation in perpetuation of WTC-associated airway disease. In future massive occupational exposure to inorganic dust/gases, we recommend early and serial pulmonary function testing, including measurements of bronchial reactivity, when possible, and inhaled corticosteroid therapy for those with symptoms or pulmonary function tests consistent with airway disease.

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.