Severity of chronic asthma
- Institute of Respiratory Medicine
- University of Sydney
- Australia
- Service de Pneumologie
- UFR Cochin-Port-Royal
- Université René
- Paris, France
- Professor A J Woolcock.
- Institute of Respiratory Medicine
- University of Sydney
- Australia
- Service de Pneumologie
- UFR Cochin-Port-Royal
- Université René
- Paris, France
- Professor A J Woolcock.
How is the severity of chronic asthma best assessed and what are the mechanisms that determine its severity? These two questions are difficult to answer because, until we understand what asthma is, it is not possible to describe its severity in a given individual. In the shorter Oxford English Dictionary severity in relation to disease is defined as “violence or acuteness of illness” or “grievousness of affliction”. The former definition is useful for exacerbations or attacks. Clinicians have had little difficulty in agreeing on defining the severity of attacks.1 2 The latter definition seems relevant to the severity of the chronic disease which is the subject of these comments. Until recently the severity of asthma was rarely assessed, but with the increasing use of guidelines and drug trials the concept of severity has emerged. The GINA guidelines1classify the disease as intermittent and persistent with severe, moderate, and mild degrees of the persistent disease. There are now a number of scores available to define the severity of asthma3-5 based on a combination of symptoms, measurements of airway function, and need for medication.
What determines the severity of asthma?
It seems likely that asthma results from the presence of both airway inflammation and abnormal behaviour of the airway smooth muscle, and severity—as measured by scores—will be determined by the factors that affect both.
AIRWAY INFLAMMATION
The gold standard for the severity of airway inflammation is the degree of histological change seen on a biopsy specimen of the airway wall. In theory, the severity is judged in terms of: the number of eosinophils, lymphocytes, the upregulation of Th2-type cytokinins in all layers of the airway wall, the amount of thickening of the wall, the epithelial damage, and the thickness of the basement membrane. Attempts have been made to correlate severity with histological measurements. Cho et al 6 …
