How should one investigate a chronic cough?

Gastroesophageal reflux disease

GERD is another common cause of cough, and the most difficult to exclude.⁵ Look for a history of reflux or heartburn and positional coughing, and have a low threshold for beginning empiric therapy. Indeed, according to the 2006 American College of Chest Physicians Cough Guideline Committee,^5,6 should a patient arrive in your clinic with a chronic cough and a normal chest radiograph who does not smoke and is not on an ACE inhibitor, then you should start empiric reflux therapy. Begin with lifestyle changes, acid suppression, and prokinetics. The cough may take 1 to 2 months before it begins to improve, and even longer to resolve.

The gold standard for diagnosis is 24-hour pH and impedance monitoring with patient self-reporting of symptoms. However, this test is not available everywhere, and there is no consensus on how to interpret the results.^1,5,6 If you strongly suspect the patient has GERD-related cough but it fails to improve with intense medical management, then refer to a specialist, as antireflux surgery may be required.

Cough-variant asthma

Cough is the only symptom of asthma in cough-variant asthma, in which the usual features of dyspnea and wheezing are absent.⁷ A methacholine challenge shows bronchial hyperresponsiveness, and asthma therapy resolves the cough.

Nonasthmatic eosinophilic bronchitis

It is important to distinguish asthma from nonasthmatic eosinophilic bronchitis,^7,8 an underdiagnosed condition. Both conditions respond equally well to treatment with inhaled or oral steroids. However, patients who have nonasthmatic eosinophilic bronchitis have normal results on spirometry and the methacholine challenge test. The diagnosis of nonasthmatic eosinophilic bronchitis is made if more than 3% of the nonsquamous cells in an induced sputum sample are eosinophils.

UNCOMMON CAUSES OF COUGH

The remaining 5% of cases of cough are caused by conditions that include bronchogenic carcinoma, chronic interstitial pneumonia, sarcoidosis, left ventricular dysfunction, use of ACE inhibitors, neurosensory cough, dynamic airway collapse, aspiration due to pharyngeal dysfunction, and psychogenic causes.¹

MULTIPLE CAUSES

Therapeutic trials will support the diagnosis. If more than one cause is suggested, start treatment in the order in which the abnormalities are discovered. If treatment is only partially successful, then pursue further causes and add to the existing treatment without stopping it.

Cough may have more than one cause, but in up to 98% of patients it can be successfully treated.

IMPORTANT POINTS

• Multiple causes of chronic cough can coexist.
• Therapeutic trials are part of the workup.
• Do not stop therapy if it is only partially successful: add to existing therapies
• Start the investigation with the most likely cause.
• Treatment is 84% to 98% successful.