Chronic cough. The spectrum and frequency of causes, key components of the diagnostic evaluation, and outcome of specific therapy.

A successful, systematic, anatomic, diagnostic protocol for evaluating patients with chronic cough was presented in 1981. To determine whether it was still valid, we prospectively evaluated, over a 22-month interval, 102 consecutive and unselected immunocompetent patients complaining of cough an average of 53 +/- 97 months (range, 3 wk to 50 yr). Utilizing the anatomic, diagnostic protocol modified to include prolonged esophageal pH monitoring (EPM), the causes of cough were determined in 101 of 102 (99%) patients, leading to specific therapy that was successful in 98%. Cough was due to one condition in 73%, two in 23%, and three in 3%. Postnasal drip syndrome was a cause 41% of the time, asthma 24%, gastroesophageal reflux (GER) 21%, chronic bronchitis 5%, bronchiectasis 4%, and miscellaneous conditions 5%. Cough was the sole presenting manifestation of asthma and GER 28 and 43% of the time, respectively. While history, physical examination, methacholine inhalational challenge (MIC), and EPM yielded the most frequent true positive results, MIC was falsely positive 22% of the time in predicting that asthma was the cause of cough. Laboratory testing was particularly useful in ruling out suspected possibilities. We conclude that the anatomic diagnostic protocol is still valid and that it has well-defined strengths and limitations.