Possible ways of defining asthma
| Method | Objection |
|---|---|
| Severity of symptoms |
Both phenotypes A and B can occur in the severe form as illustrated in the text, or in such mild forms that differentiation from normal is difficult |
| A specific number of attacks | The number of attacks experienced after 2 years of age predicts persistence of symptoms in populations but cannot safely be used in individuals (discussed in Wilson3) |
| Wheeze persisting to a certain age (for example 6-10 years) | Some children start to wheeze in later childhood. Many children wheezing in mid-childhood cease by puberty4 23 |
| Wheeze occurring at a certain age | A particular pathological basis is not necessarily limited to a particular age |
| Wheeze in atopic children | By late childhood about 40% of all children are atopic by skin testing, so that this feature is not specific; skin testing is unreliable in young childen, and is therefore insensitive for atopic asthma in this age group21 24 |
| Wheeze associated with bronchial hyper-responsiveness | The relationship between bronchial responsiveness and symptoms changes with age through early childhood17 19 |
| Any child with a doctor’s diagnosis | Often used in epidemiological studies to distinguish ‘asthma’ from ‘wheeze’25 but has no scientific value, as doctors use different criteria; for example some incorrectly label chronic cough (without wheeze) as asthma26 27 |