Persistent cough is one of the most common symptoms that brings patients to physicians' offices. Although in the majority of cases there is no serious underlying cause, a cough can adversely affect a person's quality of life until it is properly treated or resolves on its own. Irwin and Madison recently reviewed the diagnosis and treatment of this frequent problem. They define acute cough as one lasting less than three weeks, subacute as lasting from three to eight weeks and chronic cough as lasting longer than eight weeks. Although their article addresses all three types of cough, this discussion will focus on chronic cough.
When evaluating a patient whose cough has been present for at least eight weeks, a systematic evaluation to assess the most common causes followed by a trial of empiric therapy is recommended. A physical examination and a history that focus on the more common causes of chronic cough are essential. Results from numerous studies have shown that in 95 percent of immunocompetent persons, chronic cough is caused by one of the following: postnasal-drip syndrome (caused by conditions of the nose and sinuses), asthma, gastroesophageal reflux disease, chronic bronchitis from cigarette smoking, bronchiectasis, eosinophilic bronchitis or the use of an angiotensin-converting enzyme (ACE) inhibitor. The remaining 5 percent of patients have chronic cough caused by bronchiogenic carcinoma, carcinomatosis, sarcoidosis, left ventricular failure or aspiration. A psychogenic or “habit” cough is rare, according to the authors, and should always be diagnosed by exclusion.
|Nonallergic rhinitis||Dexbrompheniramine plus pseudoephedrine for three weeks, or ipratropium (0.06 %) nasal spray for three weeks|
|Allergic rhinitis||Avoidance of offending allergens; loratadine, in a dosage of 10 mg once a day|
|Vasomotor rhinitis||Ipratropium (0.06 %) nasal spray for three weeks and then as needed|
|Chronic bacterial sinusitis||Dexbrompheniramine plus pseudoephedrine for three weeks; oxymetazoline for five days; antibiotic directed against Haemophilus influenzae, Streptococcus pneumoniae and oral anaerobes|
|Asthma||Beclomethasone by metered-dose inhaler with spacer; albuterol by metered-dose inhaler with spacer, as needed|
|Gastroesophageal reflux disease||Modification of diet and lifestyle†; acid suppression; prokinetic therapy|
|Chronic bronchitis||Elimination of irritant; ipratropium, two 18-μg puffs four times daily by metered-dose inhaler with spacer|
|Angiotensin-converting enzyme inhibitors||Discontinuation of drug|
|Eosinophilic bronchitis||Inhaled budesonide, 400 μg twice daily for 14 days|
The use of a chest radiograph is important for the initial ranking of possible diagnoses and can assist in making decisions regarding empiric therapies and the need for further testing. In most cases, a normal chest radiograph in an immunocompetent patient rules out conditions such as carcinoma, tuberculosis, sarcoidosis or bronchiectasis.
Asthma may be manifested by cough alone in up to 57 percent of cases and, in general, making this clinical diagnosis can be difficult. Empiric treatment with inhaled corticosteroids and beta agonists is reasonable, but the diagnosis will only be confirmed if the cough responds to specific therapy. A definitive diagnosis can only be established by using a methacholine challenge test, which has a positive predictive value of 60 to 88 percent and a negative predictive value of 100 percent.
When investigating gastroesophageal reflux disease as a cause of chronic cough, it should be noted that about 75 percent of these patients will not have symptoms of heartburn or regurgitation. Empiric medical therapy with a proton-pump inhibitor and a prokinetic agent is recommended, along with lifestyle and dietary changes. If there is no improvement within three months, 24-hour monitoring of esophageal pH is suggested. Routine application of this diagnostic test is fraught with problems, including low positive predictive value, inconvenience and lack of consensus regarding interpretation of the results and, consequently, it should be obtained very selectively.
Cough caused by cigarette smoking, environmental irritants or medications (e.g., ACE inhibitors) ideally calls for withdrawal of the offending agent. Resolution of symptoms may take four weeks. The authors note that the character of the cough (i.e., paroxysmal, loose, productive, dry), the quality of the sound (i.e., barking, honking) and the timing of the cough (i.e., with meals, nocturnally) have not been shown to be diagnostically useful. Guidelines for treatment of common causes of chronic cough in adults are presented in the accompanying table.