Key Point

The updated ACCP cough guideline includes recommendations for bronchial disease, cancer, idiopathic pulmonary fibrosis, and unexplained cough.

MONTREAL—In medicine, the cough is king. It is the "most common complaint for which patients seek medical care," stated Richard S. Irwin, MD, Chair of Critical Care Operations at the University of Massachusetts Memorial Medical Center in Worcester.

At the annual meeting of the American College of Chest Physicians (ACCP), Dr. Irwin gave a preview of the new ACCP cough guideline published in January 2006.¹ The international committee that wrote the guideline unanimously agreed on definitions for acute, subacute, and chronic cough. An acute cough is one in which symptoms have been present for less than three weeks; a subacute cough, for between three and eight weeks; and a chronic cough, for more than eight weeks.

It was suggested that postnasal drip syndrome now be called upper airway cough syndrome. "Some physicians are so offended by using the term postnasal drip syndrome that we actually think that they fail to consider the diagnosis," Dr. Irwin remarked, "so we thought we would try a new term."

Upper airway cough syndrome, a syndrome secondary to a variety of rhinosinus conditions, is the most common cause of chronic cough. It is diagnosed by considering the combination of symptoms, findings on physical examination and sinus imaging, and ultimately, the response to specific therapy. Specific therapy is instituted when the cause of chronic cough is apparent; empiric therapy should be considered in cough of unknown etiology.

Regarding empiric therapy, the guideline strongly recommends a first-generation antihistamine/decongestant. "The postnasal drip or irritation seems to be satisfactorily controlled with anticholinergic therapy," related Dr. Irwin. "The relatively nonsedating newer antihistamines are devoid or have very little of this, so they may actually fail to win the day when the older ones will."

The patient’s response to empiric therapy should be assessed after one to three months. The failure of this therapy does not rule out acid reflux disease as the cause of chronic cough. Rather, objective investigation for acid reflux disease is necessary at this point.

A sinus-imaging study is also recommended when empiric therapy fails. "The patient could have silent sinusitis," Dr. Irwin explained.

The guideline also emphasizes diet and lifestyle modification for treating chronic cough. Treatment with a prokinetic medication should also be attempted—initially or after diet and lifestyle changes prove insufficient—before acid reflux disease is ruled out.

In another terminology change, the guideline advises that acid reflux disease be called, simply, reflux disease, unless the former term can be shown to apply. The committee did not want clinicians to believe that all cases of cough due to reflux may improve with acid suppression therapy.

Notably, leukotriene antagonists now have a defined role in treating chronic cough caused by asthma, and they can be added before escalation of therapy to systemic corticosteroids.

COUGH OCCURING IN BRONCHIAL DISEASE

In patients with cough, acute bronchitis should not be diagnosed unless pneumonia, the common cold, acute asthma, and acute exacerbations of chronic obstructive pulmonary disease have been ruled out clinically and radiographically. "Routine treatment [of acute bronchitis] with antibiotics is not justified and should not be offered," stressed Dr. Irwin. Codeine is now known to be ineffective for cough related to the common cold in adults, he added.

Exposure to cigarette smoke or other environmental irritants is generally necessary for a diagnosis of cough due to chronic bronchitis. Avoidance of environmental irritants is most effective for reducing or eliminating this form of cough, although it can persist in those with the poorest lung function.

Nonasthmatic eosinophilic bronchitis should be considered when cough is present but a chest radiograph and spirometry show normal results and there is no evidence of airway hyperresponsiveness. In these cases, cough usually responds well to inhaled corticosteroids; the dose and duration vary between patients. Occasionally, long-term prednisone treatment may be needed.

The guidelines now provide much more thorough coverage of bronchiectasis, a condition accounting for 4% to 8% of patients with chronic cough. Treatment of cough due to bronchiectasis often includes bronchodilators, anticholinergics, and oral and inhaled corticosteroids, despite the lack of evidence of a benefit.

However, "the absence of proof does not mean the absence of truth," Dr. Irwin reasoned. Giving these therapies is not wrong per se, but physicians really do not know what to say about them, he observed.

The guideline advises against giving recombinant human deoxyribonuclease specifically for cough due to bronchiectasis in patients with cystic fibrosis. While the drug clearly improves spirometry in cystic fibrosis patients, its effect on cough in these patients has not been studied.

Cough is often the only sign of nonbronchiectatic suppurative airway disease, which is mainly bronchiolitis but can also include suppurative bronchitis. After more common causes of cough are ruled out, nonbronchiectatic suppurative airway disease can be considered in patients with partially reversible or irreversible airflow limitation or with small airway disease on high-resolution CT. It should also be suspected when purulent secretions that the patient did not report are encountered and can be considered at the time of bronchoscopy.

COUGH DUE TO INFECTION, CANCER, AND FIBROSIS

Postinfectious cough is a possibility when a patient who has recently had an acute respiratory infection reports a cough lasting three to eight weeks and findings on a chest film are normal. Postinfectious cough cannot be diagnosed in cases of cough persisting for more than eight weeks, stressed Dr. Irwin, because there is a tendency for the diagnosis to be overused. He added that a cough of three to eight weeks’ duration should also trigger suspicion of Bordetella pertussis infection.

Although chronic cough is one of the most common symptoms of active tuberculosis, it is now widely accepted that tuberculosis and other lung infections are not the leading causes of chronic cough in the developing world, reported Dr. Irwin. He cited World Health Organization data showing that tuberculosis is responsible for only 1.5% of chronic coughs reported in developing nations.

Lung cancer is the cause of cough in only about 2% of cases. It is therefore recommended that chest radiography be used to assess for lung cancer in cough patients with lung cancer risk factors or malignancies that may metastasize to the lungs from other sites. Bronchoscopy is necessary when an airway malignancy is suspected or when the cause of cough has not been determined by other available tests.

The majority of patients with idiopathic pulmonary fibrosis have clinically significant cough. However, the cough is unrelated to chronic interstitial pulmonary disease in at least half of cases. Silent sinusitis is an especially common cause of cough in these patients.

"On the basis of expert opinion and only expert opinion, the diagnosis of habit or psychogenic cough can only be made after an extensive evaluation that includes ruling out tic disorders … and uncommon causes of cough," Dr. Irwin explained. To be considered psychogenic, a cough must also improve with behavior modification or appropriate psychiatric care.

IN THE CASE OF UNEXPLAINED COUGH

Like psychogenic cough, unexplained cough cannot be diagnosed until uncommon causes of cough have been ruled out. "The workup is never done unless chest CT and bronchoscopy have been performed and are normal," emphasized Dr. Irwin.

The patient must also be evaluated for cough induced by the use of a medication such as an ACE inhibitor. The only way to do this, said Dr. Irwin, is to see if the cough improves when the medication is temporarily withdrawn.

Dr. Irwin briefly described the treatment algorithm accompanying the guideline, highlighting the role of initial empiric therapy in the diagnosis and treatment of chronic cough. Success, he maintained, depends on systematically directing therapy at the most common causes of cough. "The [guideline] committee also recommends this approach for acute and subacute cough," he said.

—Timothy Begany

Reference
1. Irwin RS. How has the management of cough changed? A preview of the highlights of the revised ACCP cough clinical practice guideline. Presented at: annual meeting of the American College of Chest Physicians; November 2, 2005; Montreal, Quebec.

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