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Recommendations for the standardisation of bronchial challenge were made in 1985,1 and updated in 1993.2However, neither document recommended a single protocol or even criteria that would recommend the adoption of a particular method. Even the terminology lacks uniformity, bronchial responsiveness being used in this review in the hope that it offends the fewest number of readers. Distinction has been made, but not consistently, between (hyper)responsiveness as a general term,2(hyper)sensitivity as a leftward shift in the dose-response curve, and (hyper)reactivity as an increase in the dose-response slope.3 “Airway” and “bronchial” have been used interchangeably. The prefix “hyper” has connotations of excessive, implying a bimodal distribution in the population. Although this has not been substantiated, the acronyms BHR (bronchial hyperresponsiveness) and AHR (airway hyperresponsiveness) are well established, the former being adopted in this article.
A review of the methodology of BHR might be expected to cover all aspects of bronchial challenge, but one short article cannot provide this. Rather than reproduce recommendations which were comprehensive on most details,2 this paper emphasises variations in protocol that lead to results from different studies being non-comparable, explains how different methods of summary have arisen, and discusses the implications of these.
Variations in protocols
Whichever term for BHR is used, challenge with a pharmacological agent or with exercise in children, rather than allergen challenge, is usually implied. Subjects are assessed for eligibility, including adequate baseline lung function. Many different provocation agents have been used1; histamine and methacholine now predominate, although a number of others have recently become popular.2The aerosol generated by a nebuliser is inhaled during inspiration or tidal breathing in increasing doubling concentrations until the chosen measure of lung function has fallen by a predetermined amount from its value measured after inhalation of the diluent, the chosen …
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