Table 2

Possible ways of defining asthma

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 attacksThe 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 ageA particular pathological basis is not necessarily
 limited to a particular age
Wheeze in atopic childrenBy 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-responsivenessThe relationship between bronchial responsiveness
  and symptoms changes with age through early childhood17 19
Any child with a doctor’s diagnosisOften 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