Asthma bronchial challenge test
|
Asthma Microchapters |
|
Diagnosis |
|---|
|
Other Diagnostic Studies |
|
Treatment |
|
Case Studies |
|
Asthma bronchial challenge test On the Web |
|
American Roentgen Ray Society Images of Asthma bronchial challenge test |
|
Risk calculators and risk factors for Asthma bronchial challenge test |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Lakshmi Gopalakrishnan, M.B.B.S. [2]
Overview
Asthmatics may remain asymptomatic for a long period unless provoked by a stimuli such as a chemical irritant, an environmental allergen, cold or dry air, or rigorous exercise that may precipitate an acute attack. Bronchial challenge test is a procedure performed to provoke airway obstruction using a stimuli that is known to trigger bronchospasm, or sudden contraction of the bronchioles. This test helps to identify the specific environmental stimuli that triggers an acute attack and also helps to determine the extent of the reaction.
Bronchoprovocation Test
Bronchial hyperresponsiveness
The rationale for bronchoprovocation testing is to assess the degree of underlying bronchial hyper-responsiveness that occurs because of recurrent bronchial inflammation. Bronchial hyper-responsiveness is defined as a state of hyperactive airways that may be easily triggered by an external stimulus to precipitate an episode of bronchospasm.[1]
Mechanisms of Benefit
- Absence of bronchial hyper-responsiveness on bronchoprovocation test does rule-out the diagnosis of asthma.[2]
- Asymptomatic airway hyper-responsiveness has shown to be associated with airway inflammation and remodelling and that, the appearance of asthmatic symptoms is because of an increase in the airway inflammation.[3]
- The severity of disease has shown to be proportional to the degree of airway responsiveness.[4][5][6]
- The degree of bronchial hyper-responsiveness has shown to be beneficial in discriminating the risk of near-fatal attacks and hence predict outcomes in symptomatic patients.[7]
Test Specificity
Bronchoprovocation test is not specific for the diagnosis of asthma; however, a negative test indicated by the absence bronchial hyper-responsiveness following allergen inhalation excludes asthma.
Indication
- To identify specific environmental triggers
- Evaluation of atypical symptoms such as unexplained cough [8][9]
- Evaluation of exercise induced asthma and occupational asthma [10]
- Assessment of response to therapy
- Symptomatic patients with a normal lung function test and no reversal of symptoms with bronchodilator [11]
Procedure
- The patient's medical history is taken to evaluate for the possible triggers and a baseline spirometry is conducted to assess the lung function. Following which, under controlled circumstances, the patient is exposed to specific triggers to assess the extent of bronchial hyper-responsiveness. Spirometry tests are repeated again after inhalation of the allergen and compared with the baseline results.
- Pharmaceutical agents such as methacholine or histamine may be used as a provocative stimuli to confirm the diagnosis.[11][12][13]
- Reversibility test or a post bronchodilator test helps to assess the reversibility of airway disease and differentiate between asthma and COPD; wherein, a bronchodilator is administered before performing another round of test for comparison.
Methacholine Challenge Test
A methacholine challenge test is an adjunctive tool to diagnosis asthma. The patient breathes in nebulized methacholine that provokes narrowing of the airways resulting in bronchoconstriction. This is detected when the patient performs spirometry. People with asthma react to lower doses of inhaled methacholine.
However it is possible to have false negatives, and false positives on this test. Asthma can also be temporary, due to an exposure to noxious stimuli (smoke inhalation, etc.). Regardless of the results of a methacholine test, anyone who appears to have asthma clinically, and who responds to asthma treatment, should have asthma treatment. Asthma treatment should not be withheld in such a patient who passed a methacholine challenge.
The test is physically demanding, and the results can be affected by muscular weakness or exhaustion. Methacholine can, sometimes, stimulate the upper airway sufficiently to cause violent coughing. This can make spirometry difficult or impossible.
References
- ↑ Cockcroft DW, Ruffin RE, Dolovich J, Hargreave FE (1977) Allergen-induced increase in non-allergic bronchial reactivity. Clin Allergy 7 (6):503-13. PMID: 589783
- ↑ Crapo RO, Casaburi R, Coates AL, Enright PL, Hankinson JL, Irvin CG et al. (2000) Guidelines for methacholine and exercise challenge testing-1999. This official statement of the American Thoracic Society was adopted by the ATS Board of Directors, July 1999. Am J Respir Crit Care Med 161 (1):309-29. PMID: 10619836
- ↑ Laprise C, Laviolette M, Boutet M, Boulet LP (1999) Asymptomatic airway hyperresponsiveness: relationships with airway inflammation and remodelling. Eur Respir J 14 (1):63-73. PMID: 10489830
- ↑ Weiss ST, Van Natta ML, Zeiger RS (2000) Relationship between increased airway responsiveness and asthma severity in the childhood asthma management program. Am J Respir Crit Care Med 162 (1):50-6. PMID: 10903219
- ↑ Juniper EF, Frith PA, Hargreave FE (1981) Airway responsiveness to histamine and methacholine: relationship to minimum treatment to control symptoms of asthma. Thorax 36 (8):575-9. PMID: 7031972
- ↑ Cockcroft DW, Killian DN, Mellon JJ, Hargreave FE (1977) Bronchial reactivity to inhaled histamine: a method and clinical survey. Clin Allergy 7 (3):235-43. PMID: 908121
- ↑ Lee P, Abisheganaden J, Chee CB, Wang YT (2001) A new asthma severity index: a predictor of near-fatal asthma? Eur Respir J 18 (2):272-8. PMID: 11529284
- ↑ Rubinfeld AR, Pain MC (1976) Perception of asthma. Lancet 1 (7965):882-4. PMID: 58147
- ↑ Irwin RS, Curley FJ, French CL (1990) Chronic cough. The spectrum and frequency of causes, key components of the diagnostic evaluation, and outcome of specific therapy. Am Rev Respir Dis 141 (3):640-7. PMID: 2178528
- ↑ Vandenplas O, Malo JL (1997) Inhalation challenges with agents causing occupational asthma. Eur Respir J 10 (11):2612-29. PMID: 9426105
- ↑ 11.0 11.1 Goldstein MF, Pacana SM, Dvorin DJ, Dunsky EH (1994) Retrospective analyses of methacholine inhalation challenges. Chest 105 (4):1082-8. PMID: 8162729
- ↑ Sterk PJ, Fabbri LM, Quanjer PH, Cockcroft DW, O'Byrne PM, Anderson SD et al. (1993) Airway responsiveness. Standardized challenge testing with pharmacological, physical and sensitizing stimuli in adults. Report Working Party Standardization of Lung Function Tests, European Community for Steel and Coal. Official Statement of the European Respiratory Society. Eur Respir J Suppl 16 ():53-83. PMID: 8499055
- ↑ Covar RA, Colvin R, Shapiro G, Strunk R (2006) Safety of methacholine challenges in a multicenter pediatric asthma study. J Allergy Clin Immunol 117 (3):709-11. DOI:10.1016/j.jaci.2006.01.010 PMID: 16522478