Assessment of the patient with chronic cough.

Chronic cough, defined as cough that persists for 3 weeks or longer, is one of the most common symptoms evaluated by a primary-care physician. With the exclusion of cigarette smoking, postnasal drip, asthma, and gastroesophageal reflux are responsible for more than 80% of the causes of chronic cough. Elicitation of a thorough history and performance of a physical examination will usually provide clues about the cause of chronic cough. The use of diagnostic tests including methacholine challenge, gastroesophageal reflux studies, and sinus imaging is based on clinical suspicion. Treatment of chronic cough is aimed at the underlying cause.