Eosinophilic bronchitis as a cause of cough.

I read with interest the valuable article by Pratter et al (November 1999),1 regarding the role of sinus imaging in the management of chronic cough. Figure 2 in this article contains a useful algorithm for investigation and treatment of chronic cough. Unfortunately, one potentially important cause of cough will be missed by following this algorithm. Eosinophilic bronchitis is a recently described syndrome.2–4 Subjects with eosinophilic bronchitis have cough with eosinophilic airway inflammation characteristic of that seen in asthma; however, these patients have normal lung function, negative methacholine challenges, and no evidence of variable airflow obstruction. The cough in this condition responds nicely to inhaled corticosteroids.2–4 This syndrome would appear to be a precursor to (or perhaps the very mildest form of) symptomatic asthma. While the “purists” would not include this within the umbrella of the label asthma, it seems reasonable to consider that this is a variant of the syndrome known as cough-variant asthma. In a recent study,4 corticosteroid responsive eosinophilic bronchitis with negative methacholine challenge was shown to be present in 13% of subjects with chronic cough. The authors have pointed out the poor predictive value of a positive methacholine challenge in predicting response to asthma therapy.1,5 The relative common prevalence of eosinophilic bronchitis as a cause of cough underscores that a negative methacholine challenge is also a poor predictor of nonresponse to inhaled corticosteroids. There are two important messages. First, this questions the value of the routine use of methacholine challenges in the evaluation and management of chronic cough. It is possible that a brief diagnostic trial of high-dose inhaled corticosteroids might be a preferable tool at step 2 of the cough algorithm. Second, it suggests the potential value for standardized evaluation of sputum for inflammatory cells, particularly eosinophils, in arriving at a diagnosis and the management plan for cough.