Chronic cough, or cough that persists beyond 8 weeks, has a prevalence of 9% to 33% in all age groups. Chronic cough can cause rib fractures, syncope, anxiety, physical discomfort, and embarrassment. Treating the underlying causes of chronic cough is key to management. In some cases, it can be complicated for clinicians.
“When trying to determine the cause of chronic cough, memorizing a list of top causes can be counter-productive,” says Kaiser G. Lim, MD, author of a recent update on chronic cough that was published in Mayo Clinic Proceedings. “Instead, it’s more effective to approach chronic cough algorithmically. Physicians should consider various factors that can irritate the laryngopharyngeal area, such as polyps, granulomas, post-nasal drip, and cigarette smoking. The laryngopharyngeal area is where there is the highest concentration of cough receptors.”
Dr. Lim recommends exploring the respiratory tract below the vocal cords after the laryngopharyngeal area, considering other potential causes like bronchitis, sarcoidosis, bronchiectasis, and endobronchial tumors. “If providers consider and explore these two areas, there’s no need to memorize a list of top causes of chronic cough,” he says. He cautions clinicians to not provide purely symptom-directed treatment. Laboratory and radiographic testing should be guided by the patient history. Many intrathoracic abnormalities can be excluded with a chest x-ray, but without it, physicians can miss some types of cancer, sarcoidosis, lung collapse, and other health problems. “If a physician thinks that cough is due to airway disease,” Dr. Lim says, “then patients may mistakenly be treated for that problem without performing the necessary relevant studies.”
An Algorithmic Approach
When taking an algorithmic approach to chronic cough management, the first step is to exclude smoking, ACE inhibitors, foreign bodies, and other “low-hanging fruits” as potential causes, according to Dr. Lim (Figure). “It’s important for patients with chronic cough who are on ACE inhibitors to stop taking them,” he says. “They should be switched to an angiotensin II receptor blocker. Within 3 to 4 weeks, patients should then be reevaluated to see if their cough subsides.” If these potential causes are excluded and a single cause is likely, treatment should be provided depending on the likely cause. Likely causes of chronic cough include upper airway cough syndrome (UACS), GERD, asthma, or non-asthmatic eosinophilic bronchitis (NAEB). “If patients are able to run 5 miles every other day without shortness of breath, asthma probably isn’t the cause,” says Dr. Lim. “If patients have had heartburn 10 of the last 14 days and wake up with a bitter acid taste in the throat, they probably have typical reflux. Post-nasal drip, however, is trickier. In my experience, this usually requires rhinoscopy to examine the nasal passages.”
There can be much ‘background noise’ with UACS, GERD, asthma, and NAEB, according to Dr. Lim. Sequential treatment allows clinicians to monitor responses and check the accuracy of the working diagnosis. For example, surveys indicate that 40% to 60% of the general public reports heartburn within the past 4 weeks, but only one-third will cough. Furthermore, research suggests that only half of patients with pH probe-proven reflux have heartburn. In many cases, heartburn will likely respond to acid blockers, but cough may not. Physicians should routinely reassess after 4 to 6 weeks of treatment, to potentially save work later.
Treating Refractory Cough
When patients are referred for chronic cough that appears to be refractory to treatment despite an extensive patient work-up, Dr. Lim says it is important to examine the kind of work-ups that were performed. “In some cases, ear, nose, and throat specialists will report a non-diagnostic rhinoscopy and tell patients with chronic cough that nothing appears to be wrong, while they may have chronic sinusitis. Rhinoscopy has a sensitivity of less than 50% for picking up chronic rhinosinusitis in patients who have not had sinus surgery. Providers need to look into the nature of the cough work up and determine if the gold standard diagnostic tests have been performed.”
For all chronic cough cases, Dr. Lim stresses the importance of taking a careful, systematic approach to management. “It’s reasonable to try empiric treatments when symptoms are obvious, but specialists may need to take a step back and review prior treatment plans,” he says. “Efforts are needed to establish whether negative diagnostics were sufficiently robust to exclude specific illnesses and if treatments given were adequate. When there is no improvement in cough, physicians need to determine if it’s due to a wrong diagnosis, suboptimal or incorrect therapy, or comorbidities. Most importantly, follow-up with patients is necessary to determine if desired outcomes were attained.”