The Persistently Troublesome Cough

Over the past 25 years, a great deal has been learned about the management of cough (1); this information has been summarized recently in an evidence-based consensus panel report primarily written for cough specialists (2) that includes diagnostic algorithms for chronic cough and in a practical review article primarily directed at primary care physicians (3) that includes specific evidence-based recommendations for drug therapy and its dosing. When investigators have faithfully followed diagnostic and treatment protocols that have been shown to be successful, the cause of chronic cough has been determined 88 to 100% of the time, leading to successful therapy in 84 to 98% of the patients. Multiple studies have shown that in approximately 95% of cases involving immunocompetent patients, chronic cough results from postnasal drip syndrome, asthma, gastroesophageal reflux disease (GERD), chronic bronchitis due to cigarette smoking or other irritants, bronchiectasis, eosinophilic bronchitis, or the use of an angiotensin-converting enzyme inhibitor (2). In the remaining 5% of cases, chronic cough is caused by a variety of other diseases, such as bronchogenic carcinoma, metastatic carcinomatosis, sarcoidosis, left ventricular failure, tuberculosis, and aspiration due to pharyngeal dysfunction. A more comprehensive listing of causes has been reviewed elsewhere (4). The focus of this commentary is on the management of the adult immunocompetent patient who has a persistently troublesome cough for a duration of at least 2 months. Because, by definition, the so-called postinfectious cough resolves spontaneously within 2 months (2), that diagnosis is not considered herein. However, when a respiratory infection precedes the development of chronic cough, it is presumed that the infection led to or exacerbated other conditions commonly causing chronic cough, such as postnasal drip syndrome, symptomatic asthma, and GERD.