Comparing asthma prevalence estimates in Recife.

One of the objectives of that study was to evaluate the diagnostic accuracy of the annual prevalence of wheezing as an indicator of asthma. To do this the authors compared answers to two different questions: question 2 (Q2) of the core asthma module of the ISAAC questionnaire “Have you had wheezing in the past 12 months”? and question 6 (Q6) -“Have you ever had asthma?”. It has been previously suggested that, in the absence of a gold standard, results obtained by administering a questionnaire of the signs and symptoms of asthma can be compared to documented diagnosis of asthma made by physicians in the same patients.2 In our opinion, information obtained through Q6 cannot be taken as equivalent to a history of physiciandiagnosed asthma (clinical examination and diagnosis made by a health professional), since participants’ replies to this question will be determined by their own understanding of the term ‘asthma’ rather than by an objective measure of the presence of that disease. Therefore, the reported information seems to merely represent data on the agreement between answers to two separate questions rather than information on the validation of Q2. Validating this question would have required the comparison of replies to Q2 with results from either an objective test (e.g. lung function test), or a clinical examination by a physician, or documented information on a previous diagnosis of asthma from medical records.2 A second methodological issue is concerned with the use of the term cansaço (which in English means feeling breathless or short of breath) as part of the translation of the term "wheeze". Although the ISAAC study group had suggested that asthmatic children and their parents could be asked to describe breathing patterns during an asthma episode,3 we think that the translation of the term "wheeze" as "cansaço" used in the present study might not be appropriate. First, the term "wheeze" included in the core module of the ISAAC questionnaire corresponds to the terms "sibilos", "piado" or "chiado", in Brazilian Portuguese. In contrast, the term "cansaço" (shortness of breath) has a broader meaning and, in the Brazilian context, it is frequently associated with several clinical conditions other than asthma. Second, the English version of the questionnaire that was used in phase I of the ISAAC only included the terms "wheeze", "cough" and "asthma" (and not "breathless" or "short of breath").4 The term "breathless" or "short of breath" was only introduced later in the English version of the phase II ISAAC core questionnaire (module Wheeze and Breathlessness Supplementary Questionnaire).3 It is worth noting that the term "cansaço" did also not appear in the Brazilian version of the questionnaire designed to be used in Phase I of the ISAAC in Brazil.5 Finally, other three English versions of questionnaires designed to study respiratory diseases have used the terms "wheeze", "breathless" and "short of breath" in separate questions or as "shortness of breath with wheezing" (IUATLD, ATS and MRC).2 And it has been shown that questions that use the terms "breathless" and "short of breath" have lower specificity in correctly identifying asthma than those using the term "wheeze".2