EDITORIAL Neutrophils, airway hyperresponsiveness and COPD: true, true and related?

nce upon a time distinguishing between COPD and asthma in a smoking or ex-smoking patient was easy: a patient who smoked, had a low diffusing capacity of the lung for carbon monoxide or a hyperlucent radiogram, and no bronchodilator response was labelled as COPD; whereas a patient who, whether they smoked or not, had a broncho-dilator response and airway hyperresponsiveness (AHR) was an asthmatic. Nothing could be simpler; that is until studies of asthmatics included measurements of inflammation and studies of patients with COPD included performing methacho-line challenges. We now know that significant bronchodilator responses can be present in many patients with COPD [1] and, as discussed below, airway responsiveness is also not a stable feature of asthma. As determined by unbiased analysis, such as cluster or factor analysis, asthma [2, 3] and COPD [4] both hav