https://doi.org/10.4081/monaldi.2026.3788
Variable expiratory airflow, and not airway obstruction, is the defining physiological feature of asthma
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.
Accepted: 23 September 2026
Published: 12 October 2026
Asthma is usually diagnosed by history and presence of airway obstruction with a significant bronchodilator response on spirometry. However, airway obstruction may not always be present, or a bronchodilator response may not be significant. Contrary to wide perception, airway obstruction is not the defining functional feature of asthma. Definitions of asthma have never included the term ‘airways obstruction’. According to the Global Initiative for Asthma, the diagnosis of asthma requires a history of typical variable symptoms and confirmation by variable expiratory airflow. It has emphasized that variable expiratory airflow is the key physiological feature of asthma. Airway obstruction is a manifestation of this variability and represents one end of the spectrum of this variation. When airways obstruction is observed, a positive bronchodilator response is the most convenient method to confirm the diagnosis. However, when airway obstruction or bronchodilator responsiveness is not demonstrable, there are other options to demonstrate variability in not demonstrable, there are other options to demonstrate variability of expiratory airflows and confirm the diagnosis.
Downloads
Pellegrino R, Viegi G, Brusasco V, et al. Interpretative strategies for lung function tests. Eur Respir J 2005;26:948-68. DOI: https://doi.org/10.1183/09031936.05.00035205
Quanjer PH, Tammeling GJ, Cotes JE, et al. Lung volumes and forced ventilatory flows. 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 1993;16:5-40. DOI: https://doi.org/10.1183/09041950.005s1693
Stanojevic S, Kaminsky DA, Miller MR, et al. ERS/ATS technical standard on interpretive strategies for routine lung function tests. Eur Respir J 2022;60:2101499. DOI: https://doi.org/10.1183/13993003.01499-2021
Global Initiative for Asthma. Global strategies for asthma management and prevention. 2026 Update. Available from: https://ginasthma.org/2026-gina-strategy-report.
Pascual RM, Peters SP. The irreversible component of persistent asthma. J Allergy Clin Immunol 2009;124:883-90. DOI: https://doi.org/10.1016/j.jaci.2009.09.047
Chhabra SK, Bhatnagar S. Comparison of bronchodilator responsiveness in asthma and chronic obstructive pulmonary disease. Indian J Chest Dis Allied Sci 2002;44:91-7.
Walker PP, Calverley PM. The volumetric response to bronchodilators in stable chronic obstructive pulmonary disease. COPD 2008;5:147-52. DOI: https://doi.org/10.1080/15412550802092928
Aaron SD, Vandemheen KL, FitzGerald JM, et al. Canadian respiratory research network. Reevaluation of diagnosis in adults with physician diagnosed asthma. JAMA 2017;317:269-79. DOI: https://doi.org/10.1001/jama.2016.19627
Bertels X, Edris A, Garcia-Aymerich J, et al. Phenotyping asthma with airflow obstruction in middle-aged and older adults: a CADSET clinical research collaboration. BMJ Open Respir Res 2023;10:e001760. DOI: https://doi.org/10.1136/bmjresp-2023-001760
Scadding JG. Definition and clinical categories of asthma. In: Clark TJH, Godfrey S, eds. Asthma 2nd ed. London, UK: Chapman and Hall; 1983.
Chhabra SK, Kumar R, Gupta U, et al. Prediction equations for spirometry in adults from northern India. Indian J Chest Dis Allied Sci 2014;56:221-5. Erratum in: Indian J Chest Dis Allied Sci 2015;57:204.
How to Cite
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
PAGEPress has chosen to apply the Creative Commons Attribution NonCommercial 4.0 International License (CC BY-NC 4.0) to all manuscripts to be published.