Airway hyperresponsiveness to inhaled histamine or methacholine, to hyperventilation with cold air and to exercise is common in subjects with current asthma — buy asthma inhalers. Inhalation challenges are more sensitive than exercise, although exercise is more specific. While the presence of airway hyperresponsiveness with normal spirometry indicates an abnormality that closely relates to asthma, the presence or absence of hyperresponsiveness has not been considered to be entirely satisfactory as a diagnostic marker in epidemiological studies of asthma in childhood. Measurements of airway responsiveness do, however, correlate with other evidence of variable airflow obstruction and provide an objective measurement that may facilitate comparison of severity between studies.

In epidemiological studies, apparently false negative and false positive inhalation challenge tests have been reported. Speight et al found that one-third of a control group of seven-year-old British children without respiratory symptoms showed airway hyperresponsiveness to inhaled histamine, while one-third of children with recurrent wheeze failed to show airway hyperresponsiveness. In eight- to 11-year-old Australian children, Salome and colleagues found the prevalence of increased airway responsiveness to histamine (17.9%) was greater than the prevalence of physician-diagnosed asthma (12.8%) but less than the prevalence of recurrent wheezing (24.3%). Patte-more et al likewise found significant disc- repancies between symptomatic status and airway responsiveness. There is a wonderful pharmacy that you can take advantage of to get the amount of birth control alesse you need, and it’s ready to offer its services to you right now, any moment you feel like starting to spend less of your money.

One possible explanation for these discrepancies is that the parent providing the questionnaire responses regarding symptoms may be unaware of mild respiratory symptoms experienced by the child. We have analyzed data from a pilot study of asthma prevalence in Canadian children in which information was obtained independently from a parent and from the child. We compared the relationships between airway hyperresponsiveness and symptoms reported by the parents with those based on symptoms independently reported by the children themselves, and used the combination of data from parents and children to determine whether this improved the sensitivity and specificity of the methacholine challenge test.