Chronic cough is a common symptom that causes major life disruptions for afflicted persons. The prevalence of chronic cough among nonsmokers is estimated to range from 14 to 23 percent. Palombini and associates studied patients with a history of chronic cough in an attempt to determine the primary causes and evaluate the use of an anatomic protocol. They described the spectrum and frequency of the causes of chronic cough, analyzed the results of diagnostic testing and included the response to specific therapy as a diagnostic criterion.

The authors studied patients over the age of 12 who had a cough for at least three weeks and a normal chest radiograph. Patients who smoked were excluded. All patients underwent a history and physical examination as well as computed tomography (CT) of the chest and sinuses, blood and sputum studies, fiberoptic rhinoscopy and bronchoscopy, skin tests for inhalable antigens, spirometry with a carbachol inhalation challenge and 24-hour pH monitoring. For pretreatment diagnosis, specific criteria based on current medical literature were applied. These conditions included postnasal drip syndrome, asthma, gastroesophageal reflux disease, bronchiectasis and tracheobronchial collapse.

The patients underwent a variety of medical treatments depending on the presumptive diagnosis. Some therapies prescribed were nasal steroids, inhaled steroids, systemic steroids, bronchodilators, antihistamines, decongestants and histamine H₂-receptor blockers. Treatments were considered successful if the cough completely abated or was well-controlled. Most patients were followed for 12 months. A final diagnosis for the cause of the cough was made on the basis of a patient fulfilling the pretreatment criteria and post-treatment resolution of cough.

Seventy-eight patients (27 males, 51 females) participated in the study. The mean age was 57 years, with a range of 15 to 81 years. The mean duration of cough was 72 months, and the number of physicians seen in the past for the problem was approximately eight per patient. The authors established a diagnosis in all 78 patients, and the response rate to treatment was 94 percent. Of the five patients who did not respond to therapy, three had tracheobronchial collapse, one had a goiter and one had middle lobe syndrome. All three of these conditions are indications for surgery.

The five most common causes of chronic cough in order of frequency were asthma (46 patients), postnasal drip syndrome (45 patients), gastroesophageal reflux disease (32 patients), bronchiectasis (14 patients) and tracheobronchial collapse (11 patients). Forty-eight patients were found to have more than one cause for chronic cough; all had one or more of the three most common diagnoses (asthma, postnasal drip syndrome and gastroesophageal reflux disease). Twenty-six patients had two components of the triad, and 12 patients were found to have all three diagnoses.

Of the entire series of patients, 94 percent had at least one of the triad components. Because of this significant frequency, the authors propose that the term “pathogenic triad of chronic cough ” be introduced into the medical literature (see accompanying figure).

The authors conclude that because 62 percent of their patients had more than one cause for chronic cough, most patients will need several diagnostic studies to find a reason for chronic cough. Considering their findings, they recommend that CT studies of the sinuses, esophageal pH monitoring and carbachol inhalation challenge be considered for the initial evaluation. Although this approach may not be cost effective, the authors note that a recent report of the Cough Consensus Panel of the American College of Chest Physicians does not support empiric treatment of chronic cough without some degree of diagnostic work-up. However, what is best from a cost-effective standpoint remains to be determined by future studies.