ORIGINAL ARTICLE Comparing and combining studies of bronchial

Background: There is no standardised protocol for the measurement of bronchial responsiveness. Results from different studies are difficult to compare and combine. Methods: Analyses are divided between those of a continuous outcome, which can be directly stand-ardised as effect size, and those based on a binary outcome. A published method is used to convert an odds ratio to equivalent effect size. Results: The use of effect size allows comparison between studies using a continuous outcome but dif-ferent protocols, provided the relevant standard deviation is reported. Effect size from a continuous out-come and that derived from an odds ratio from an equivalent analysis gave similar results. Conclusions: Systematic reviews which include both continuous effect estimates and odds ratios can include both in one meta-analysis, provided relevant standard deviations are published for the former. Authors are encouraged to report these in all fields in which measurement protocols vary. The measurement of bronchial responsiveness (BHR) isadvocated in population studies of asthma.1 While notsynonymous with asthma, it is an objective measure that has particular advantages in multicultural studies.2 BHR has also been used in the diagnosis of asthma and the measurement of severity in clinical settings.