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==Overview== | ==Overview== | ||
Asthmatics may remain asymptomatic for a long period unless provoked by a stimuli such as a chemical irritant, an [[allergen|environmental allergen]], cold or dry air, or [[exercise induced asthma|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 [[muscular contraction|contraction]] of the [[bronchioles]]. This test helps to identify the specific environmental stimuli that [[Asthma risk factors|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]].<ref name="pmid589783">Cockcroft DW, Ruffin RE, Dolovich J, Hargreave FE (1977) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=589783 Allergen-induced increase in non-allergic bronchial reactivity.] ''Clin Allergy'' 7 (6):503-13. PMID: [http://pubmed.gov/589783 589783]</ref> | |||
====Mechanisms of Benefit==== | |||
*Absence of bronchial hyper-responsiveness on bronchoprovocation test does rule-out the diagnosis of asthma.<ref name="pmid10619836">Crapo RO, Casaburi R, Coates AL, Enright PL, Hankinson JL, Irvin CG et al. (2000) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=10619836 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: [http://pubmed.gov/10619836 10619836]</ref> | |||
*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.<ref name="pmid10489830">Laprise C, Laviolette M, Boutet M, Boulet LP (1999) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=10489830 Asymptomatic airway hyperresponsiveness: relationships with airway inflammation and remodelling.] ''Eur Respir J'' 14 (1):63-73. PMID: [http://pubmed.gov/10489830 10489830]</ref> | |||
*The severity of disease has shown to be proportional to the degree of airway responsiveness.<ref name="pmid10903219">Weiss ST, Van Natta ML, Zeiger RS (2000) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=10903219 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: [http://pubmed.gov/10903219 10903219]</ref><ref name="pmid7031972">Juniper EF, Frith PA, Hargreave FE (1981) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=7031972 Airway responsiveness to histamine and methacholine: relationship to minimum treatment to control symptoms of asthma.] ''Thorax'' 36 (8):575-9. PMID: [http://pubmed.gov/7031972 7031972]</ref><ref name="pmid908121">Cockcroft DW, Killian DN, Mellon JJ, Hargreave FE (1977) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=908121 Bronchial reactivity to inhaled histamine: a method and clinical survey.] ''Clin Allergy'' 7 (3):235-43. PMID: [http://pubmed.gov/908121 908121]</ref> | |||
*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.<ref name="pmid11529284">Lee P, Abisheganaden J, Chee CB, Wang YT (2001) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=11529284 A new asthma severity index: a predictor of near-fatal asthma?] ''Eur Respir J'' 18 (2):272-8. PMID: [http://pubmed.gov/11529284 11529284]</ref> | |||
====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 [[Asthma risk factors|environmental triggers]] | |||
*Evaluation of atypical symptoms such as unexplained cough <ref name="pmid58147">Rubinfeld AR, Pain MC (1976) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=58147 Perception of asthma.] ''Lancet'' 1 (7965):882-4. PMID: [http://pubmed.gov/58147 58147]</ref><ref name="pmid2178528">Irwin RS, Curley FJ, French CL (1990) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=2178528 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: [http://pubmed.gov/2178528 2178528]</ref> | |||
*Evaluation of [[exercise induced asthma]] and [[occupational asthma]] <ref name="pmid9426105">Vandenplas O, Malo JL (1997) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=9426105 Inhalation challenges with agents causing occupational asthma.] ''Eur Respir J'' 10 (11):2612-29. PMID: [http://pubmed.gov/9426105 9426105]</ref> | |||
*Assessment of response to therapy | |||
*Symptomatic patients with a [[PFTs|normal lung function test]] and no reversal of symptoms with [[Bronchodilator#Short-acting β2-agonists|bronchodilator]] <ref name="pmid8162729">Goldstein MF, Pacana SM, Dvorin DJ, Dunsky EH (1994) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=8162729 Retrospective analyses of methacholine inhalation challenges.] ''Chest'' 105 (4):1082-8. PMID: [http://pubmed.gov/8162729 8162729]</ref> | |||
====Procedure==== | |||
*The patient's [[Asthma history and symptoms|medical history]] is taken to evaluate for the possible [[Asthma risk factors|triggers]] and a baseline [[Asthma pulmonary function test#Spirometry|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.<ref name="pmid8162729">Goldstein MF, Pacana SM, Dvorin DJ, Dunsky EH (1994) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=8162729 Retrospective analyses of methacholine inhalation challenges.] ''Chest'' 105 (4):1082-8. PMID: [http://pubmed.gov/8162729 8162729]</ref><ref name="pmid8499055">Sterk PJ, Fabbri LM, Quanjer PH, Cockcroft DW, O'Byrne PM, Anderson SD et al. (1993) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=8499055 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: [http://pubmed.gov/8499055 8499055]</ref><ref name="pmid16522478">Covar RA, Colvin R, Shapiro G, Strunk R (2006) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=16522478 Safety of methacholine challenges in a multicenter pediatric asthma study.] ''J Allergy Clin Immunol'' 117 (3):709-11. [http://dx.doi.org/10.1016/j.jaci.2006.01.010 DOI:10.1016/j.jaci.2006.01.010] PMID: [http://pubmed.gov/16522478 16522478]</ref> | |||
*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== | ==Methacholine Challenge Test== | ||
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Revision as of 15:13, 23 September 2011
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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