Airway hyperresponsiveness by methacholine challenge testing following negative exercise challenge

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

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

Methacholine challenge testing is superior to the exercise challenge for detecting asthma in children

BACKGROUND

Exercise-induced bronchoconstriction occurs in a large proportion of children with asthma.

OBJECTIVE

To compare the predictive value of methacholine challenge testing (MCCT) and the exercise treadmill challenge (ETC) for detecting asthma in children with postexercise symptoms.

METHODS

This was a prospective study of children 10 to 18 years old with postexercise symptoms. During asthma diagnosis, they underwent MCCT and ETC. There were 2 study visits. All subjects underwent ECT at visit 1 and MCCT 1 week later at visit 2.

RESULTS

One hundred one children were included; 62.9% had a history of atopy, and asthma was confirmed in 43.6%. MCCT showed 90.9% sensitivity, 82.5% specificity, 80.0% positive predictive value, and 92.2% negative predictive value; the respective values for ECT were 77.3%, 68.4%, 65.4%, and 79.6%. Positive MCCT results showed significantly higher sensitivity and higher positive predicative value in the diagnosis of asthma in children with postexercise symptoms compared with a 10% decrease in forced expiratory volume in 1 second for ECT (P = 0.034). Conducting MCCT during asthma diagnosis confirmed asthma in an additional 24.3% of children with exercise-induced symptoms. With a cutoff level at 17% of forced expiratory volume in 1 second for ECT, the discrepancy was decreased and reasonable values for sensitivity, specificity, positive predictive value, and negative predictive value were attained (61.0%, 77.1%, 69.4%, and 69.8%, respectively).

CONCLUSION

A large number of school children with asthma and postexercise symptoms could have positive MCCT and negative ECT findings. Untreated asthma in children with exercise-induced bronchoconstriction could cause them to be discharged from physical education classes.

TRIAL REGISTRATION

www.ClinicalTrials.gov, identifier NCT01798823.

Methacholine challenge is insufficient to exclude bronchial hyper-responsiveness in a symptomatic military population

BACKGROUND

Bronchial hyper-responsiveness in a military population has been evaluated by direct and indirect challenge methods. We hypothesized that negative methacholine challenge testing (MCT) was not sufficient to exclude significant bronchial hyper-responsiveness in a symptomatic military population with exertional dyspnea. The purpose of our study was to identify bronchial hyper-responsiveness in symptomatic military recruits and active duty personnel with normal baseline spirometry and negative pharmacologic bronchoprovocation testing.

METHODS

We performed a retrospective single center electronic chart review of symptomatic service members with a negative MCT who completed a subsequent exercise challenge test (ECT).

RESULTS

ECT was positive in 45 (26.4%) of 171 subjects (98 recruits). Subjects with a positive ECT had lower baseline forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC) and FEV1/FVC than those with a negative ECT, and these differences were statistically significant. The mean drop in FEV1 with exercise challenge positive patients was 17.9 ± 9.2%, and the mean drop in FEV1 with MCT was significantly greater in exercise challenge positive patients (-9.5 ± 5.5 vs. -7.6 ± 5.5, p = 0.042). Exercise-induced bronchoconstriction (EIB) was observed in 41% of all recruits who subsequently did not complete training. Only 1 recruit subject of 28 with EIB completed training.

CONCLUSIONS

Methacholine challenge is an insufficient screening test to detect bronchial hyper-responsiveness in a symptomatic military population. In military recruits, EIB is associated with training failure.

Evaluation of fitness to utilize Self-Contained Breathing Apparatus (SCBA)

BACKGROUND

Breathing dry, cold air may cause bronchoconstriction in asthmatics working with self-contained breathing apparatus (SCBA). Air delivered by SCBA is cooler than ambient air. It is unclear whether a bronchial challenge test using mannitol (BCTM) can predict a fall in forced expiratory volume in one second (FEV(1)) during exercise with SCBA.

METHODS

A prospective study of army recruits assigned to work with SCBA was carried out. Participants completed self-administered questionnaires on respiratory symptoms, BCTM, and measurement of exhaled nitric oxide. A subgroup of participants with a positive BCTM (BTCM+) and with negative BCTM underwent exercise test on bicycle ergometer (ET) while using SCBA.

RESULTS

One hundred and six recruits participated in this study. One hundred and two underwent BCTM and 28 ET. Nineteen out of 97 participants had a positive BCTM and 6 out of 27 had a positive ET. Seventeen out of 19 participants with a positive BCTM had current respiratory symptoms such as wheeze, cough, chest tightness, or dyspnea. Sensitivity, specificity, positive predictive value, and negative predictive value for a positive ET under SCBA were 100%, 64%, 43%, and 100% for the BCTM, respectively. BCTM-positive participants with respiratory symptoms had more physician consultations during MBT compared to BCTM-negative participants.

CONCLUSION

Despite medical evaluation and exclusion of asthmatics by a physician during conscription, a high proportion of recruits assigned to work with SCBA smoke, have respiratory symptoms, and have a positive BCTM suggesting current asthma. BCTM has a high sensitivity to predict a significant fall in FEV(1) after exercise with SCBA and participants with a positive BCTM tend to use more health care resources during basic military training. Recruits should be counseled about smoking cessation prior and during basic military training.

Airway hyperresponsiveness: a comparative study of methacholine and exercise challenges in seasonal allergic rhinitis with or without asthma

BACKGROUND

Asymptomatic airway hyperreactivity in allergic rhinitis is a risk factor for later development of asthma. Although non-specific bronchial hyperresponsiveness (BHR) has been measured by several stimuli, the most appropriate measurement technique still remains unclear.

OBJECTIVE

To investigate whether an exercise challenge can be used to predict BHR in seasonal allergic rhinitis patients with or without asthma and to compare this bronchial reactivity with a methacholine challenge technique.

METHODS

Forty-six consecutive patients with seasonal allergic rhinitis only (n = 31) and with both seasonal allergic rhinitis and asthma (n = 15) were included in the study during the pollination period. Subjects underwent first methacholine (mch) and then exercise challenge testing (ECT). There was a 1-week interval between the tests. ECT was performed on a bicycle ergometer. Positive result was defined as a 15% decrease in forced expiratory volume in 1 second (FEV(1)) post-exercise. A patient's bronchial reactivity to methacholine was considered as hyperresponsive if PC(20) was less than 8 mg/mL.

RESULTS

Mch PC(20) values were significantly lower in patients with both rhinitis and asthma (p < 0.062). Among the 46 patients, mch PC(20) values were significantly different between patients who had positive and negative exercise challenge tests (p = 0.007). All patients with rhinitis alone had a negative ECT and 10 had a positive mch challenge. Change in FEV(1) values after ECT was significantly higher in patients with both rhinitis and asthma compared to those with rhinitis alone (p = 0.009). There was a significant relation between positivity of mch and exercise challenges (p = 0.025). ECT positivity was found to be a significant confounding factor in the diagnosis of asthma (p = 0.001). Specificity and sensitivity values were 100% and 24% for ECT and 68% and 100% for mch, respectively.

CONCLUSION

Exercise challenge presents poor diagnostic value for detecting bronchial responsiveness in individuals with allergic rhinitis alone during the pollen season.

Response to bronchodilators after exercise challenge predicts bronchial hyperreactivity

BACKGROUND

Some subjects with suspected asthma and a negative exercise challenge test (ECT) demonstrate improved expiratory flow rates after administration of bronchodilators (BD) at the end of the ECT (unpublished observation). This study investigated whether this response predicts the presence of bronchial hyperreactivity (BHR).

PATIENTS AND METHODS

The study population included 133 young adults (29.4% women) 21.1 +/- 4.2 years of age who underwent ECT and a methacholine challenge test (MCT). A receiver-operator-characteristic curve was used to calculate the optimal cutoff level of the response to BD as a predictor of BHR according to MCT.

RESULTS

Using a MCT cutoff level of PC(20) </= 4 mg/mL showed BHR in 12.8% of subjects. Failure to improve FEV(1) by 8% after BD administration predicted the absence of BHR with sensitivity, specificity, and positive and negative predictive values of 76.5%, 68.4%, 25.3%, and 95.5%, respectively. Avoiding MCT in subjects with less than 8% response to BD would have saved 62.5% of the MCTs and would have missed only four (3%) patients with BHR.

CONCLUSIONS

BD should be administered routinely after ECT, as the response may be used as a simple, inexpensive tool to predict BHR in young patients and may substantially reduce the number of unnecessary MCTs.

Increased airway hyperreactivity with the M40 protective mask in exercise-induced bronchospasm

OBJECTIVE

Exercise-induced bronchospasm (EIB) has a prevalence of 6% to 7% in United States Army personnel and 3% to 13% in professional athletes. There are reported concerns that military personnel with EIB will have increased airway hyperreactivity or significant dyspnea while wearing the standard military M40 protective mask. The objective of this study is to determine whether the M40 protective gas mask increases airway hyperreactivity in military personnel with exertional dyspnea and the diagnosis of EIB.

METHODS

Ten active duty military with EIB (defined as history of exertional dyspnea, normal spirometry, and reactive methacholine challenge test) and 10 normal control subjects were evaluated. Both the participants and control subjects underwent baseline exercise challenge testing (ECT) with and without the M40 protective mask. Forced expiratory volume in one second (FEV1) (percent predicted) post ECT was compared to baseline FEV1 within and between groups along with exercise time.

RESULTS

There was no statistical difference in between individuals and between groups wearing the M40 mask. None of the study group had a positive ECT exercising without the M40 mask while 20% of the study group with EIB had a positive ECT wearing the M40 mask.

CONCLUSION

Military personnel with EIB who exercised with the M40 protective mask did not overall have significantly increased airway hyperreactivity compared to control subjects. Screening ECT may be beneficial in identifying those susceptible persons who report symptoms while wearing the M40 protective mask.