DISCUSSION

Our study confirms the finding of one other recently reported comparison of parent- and child-completed questionnaires in another country and in older children. Among 271 13-to 14-year-old children in Germany, wheezing in the past year was reported on both questionnaires in 12.1%, by the parent but not the child in 8.3%, by the child but not the parent in 9.1% and denied by both in 70.6%. The proportions responding similarly regarding diagnosed asthma were 14.2%, 1.5%, 8.4% and 75.8%, respectively. That study also found that sensitivity and specificity for airway responsiveness and symptoms or diagnoses were similar whether reported by the parent or by the child. Among Boston 14-year-olds, children reported wheezing 2.4 times more frequently than did their parents. Validation of responses by measurements of airway responsiveness was not reported.

Even though answers to parent-completed questionnaires were closely related to measurements of airway responsiveness, they are also subject to some uncertainty. Peat et al recently reported that a second administration of the questionnaire used in this study resulted in 7% of children changing diagnosed asthma category, 13% changing cumulative wheeze category and 9% changing recent wheeze category. Hence, there is considerable variability in results from prevalence studies as a result of the lack of precision of questionnaire data.
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The prevalence of airway hyperresponsiveness to metha-choline not associated with any current or past history of symptoms suggesting asthma including wheezing, coughing and dyspnea was higher among this sample than in previous studies. The study was conducted during winter months when there may have been a higher prevalence of respiratory tract infection leading to temporary airway hyperresponsiveness, but it should not have been influenced by the pollen season, which was largely over when the study commenced. The method of methacholine challenge used in the study differed from the abbreviated techniques used in New Zealand and Australia. This is unlikely to account for the difference in prevalence and degree of airway responsiveness, because these methods yield very similar results in direct comparison. It was not possible to employ these abbreviated methods in this study to achieve more direct international comparisons, because the method of Cockcroft et al was at the time the only method approved by Health and Welfare Canada for methacholine challenge in Canada.