Definition of Asthma
Why do we define asthma?
We define asthma to identify the disease correctly and to differentiate it from other diseases. To fulfill this goal, definition of asthma has been changing over last 40 years. The clinician, physiologist, immunologist, pathologist or epidemiologist - all have different perspective of asthma.
In the year 1997, the following working definition has been formulated by Expert Panel-2 of National Asthma Education and Prevention Program, USA.
Asthma is a chronic inflammatory disorder of the airways:
in which many cells & cellular elements play a role: in particular, mast cells, eosinophils, T lymphocytes, macrophages, neutrophil & epithelial cells.
- In susceptible individuals, this inflammation causes recurrent episodes of wheezing, breathlessness, chest tightness and coughing, particularly at night or in the early morning.
- These episodes are usually associated with widespread but variable airflow obstruction that is often reversible either spontaneously or with treatment.
- The inflammation also causes an associated increase in the existing bronchial hyper-responsiveness to a variety of stimuli.
- Moreover recent evidence indicates that sub-basement membrane fibrosis may occur in some patients with asthma and that these changes contribute to persistent abnormalities in lung function.
This definition consists of five components :
- Nature of disease
- Cardinal features
- Reversible obstruction in pulmonary function testing
- Hyper responsiveness to multiple stimuli
- Cause of persistent asthma
This definition is to some extent a complete definition. The critical role of inflammation in asthma is so important that it is described in the first component of the definition.
We can summaries this definition in a simple form:
Asthma is a chronic inflammatory disorder causing hyper responsiveness of airways to certain stimuli resulting in recurrent variable airflow limitation, at least partly reversible, presenting as wheezing, breathlessness, chest tightness and coughing.
- Asthma and Allergy Foundation of America: http://www.aafa.org/
- American Asthma Foundation: http://www.americanasthmafoundation.org/
- Asthma, UK: http://www.asthma.org.uk/all_about_asthma/index.html
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