Bronchodilator responsiveness: interpret with caution

Bronchodilator responsiveness (BDR) is widely considered to be a key diagnostic criterion for asthma, and is used to differentiate asthma from chronic obstructive pulmonary disease (COPD). Currently, the threshold of a 12% increase in FEV1 from baseline following inhaled salbutamol, with at least a 200 ml increase in absolute terms, is recommended as a response indicative of asthma,1 although recent British guidelines recognise the poor discriminatory function of this criterion.2 Thus, despite this criterion being commonly used in clinical practice, there is uncertainty regarding its clinical utility, in particular its ability to differentiate asthma from COPD, or indeed, normal subjects. One approach to enable a better understanding of the clinical utility of BDR is to determine the worldwide distribution of BDR in health and disease, which has been undertaken by Tan and colleagues, and reported in Thorax.3 The authors report BDR in terms of change in FEV1 and FVC following 200 μg of salbutamol delivered by metered dose inhaler via a spacer, in around 10 000 adults aged 40 years and older from 14 countries in North America, Europe, Asia and Africa who participated in the Burden of Obstructive Lung Disease study. The Burden of Obstructive Lung Disease methodology is robust and has many strengths, …