In the clinic however patients frequently straddle diagnostic boundaries and the further description of subtypes expands the numbers of “diseases” causing cough. Is this a form of asthma? Some would suggest that this is a separate condition. Here there is no bronchial hyperresponsiveness but evidence, usually obtained at induced sputum, of eosinophilic inflammation within the airways. However, an even more bizarre form of ‘asthma’, known as eosinophilic bronchitis, was also clearly a significant cause of cough in the clinic. These patients with cough variant or cough predominant asthma were suggested to have a differential location of the inflammation within the airway. Thus, patients with ‘asthmatic cough’ sometimes did not wheeze, a symptom most would regard as sine qua non of asthma. Firstly, when one of the three diagnostic labels was attached to a patient further investigation frequently revealed a grossly atypical pattern of disease. To many working in the field this classification was deeply unsatisfactory.
The term idiopathic cough was duly coined to overcome the difficulties arising from the failure to pigeonhole such awkward patients. Unfortunately, for those promulgating this paradigm patients presenting to the clinic often failed to fit into these diagnostic categories. Cough was either due to a form of asthma, gastroesophageal reflux disease, or a nebulous and poorly defined condition variously called, Post Nasal Drip Syndrome or the Upper Airways Cough Syndrome. Indeed, this hypothesis was crystallised into ‘the diagnostic triad of cough’. In the 1980s patients presenting with isolated chronic cough were suggested to fall into one of three diagnostic categories.
Our continuing difficulty in dealing with patients presenting with chronic cough is an example of an established dogma failing to measure up to awkward clinical facts.
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