Author's response: 1

Wheeze in the past 12 months is now the most widely used definition for asthma in epidemiological studies 2 3 and, although we agree it may be subject to some misclassification, such a definition has three important advantages: (1) simplicity, permitting widespread use in epidemiological studies; (2) the definition is more inclusive and, where a word for the symptom exists in the local language that is linked culturally with asthma, may be less subject to bias in poor populations (see below); and (3) its wide use permits comparison between studies of the role of potential risk factors and more powerful analyses across studies of potential risk factors with a wide range in the prevalence of exposure.