NR 511 Week 3 Differential for Chronic Cough Example

Differential Write-Up: Ten Weeks of Dry Cough in a 55-Year-Old Never-Smoker Who Started Lisinopril Five Months Ago, Four Candidates Given Equal Treatment, and the Order in Which They Can Be Tested

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College of Nursing, Chamberlain University

NR 511: Differential Diagnosis and Primary Care Practicum

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Month Day, Year

Differential Write-Up: Ten Weeks of Dry Cough in a 55-Year-Old Never-Smoker Who Started Lisinopril Five Months Ago, Four Candidates Given Equal Treatment, and the Order in Which They Can Be Tested

The Presentation, Compressed

Mrs. L. A. is a 55-year-old school cafeteria manager who has never smoked. For ten weeks now she has been bothered by a dry cough that tickles. It is worse at night and when she talks for long periods, and she clears her throat often. She started lisinopril 10 mg daily five months ago for hypertension, and the cough began about two months after that. She has seasonal allergic rhinitis, which she treats with an oral antihistamine in spring, and she notes a sensation of mucus dripping down the back of her throat most mornings. She gets heartburn after large evening meals about twice a week. She denies wheeze, shortness of breath, fever, night sweats, weight loss and blood in her sputum. There are no pets at home and no new exposures at work. On examination she is afebrile with an oxygen saturation of 98% on room air. The nasal mucosa is pale and boggy, and the posterior pharynx shows a cobblestone pattern with a thin film of clear mucus. The lungs are clear, with no wheeze on forced expiration. A chest radiograph taken at an urgent care center three weeks ago was reported as normal.

Once an adult's cough passes the eight-week mark it counts as chronic, and the approach recommended by the American College of Chest Physicians starts with history, examination and a chest radiograph, and asks specifically about an angiotensin-converting enzyme (ACE) inhibitor (Irwin et al., 2018). The four candidates below are the ones this patient's findings raise. Each is given the same three moves: what raises it, what weakens it, and what is still unknown.

Candidate 1: ACE Inhibitor Cough

What raises it. She takes lisinopril, and the cough is dry, tickling and nonproductive, which is the usual character of this cough. Dicpinigaitis (2006) reported that its incidence in patients taking these drugs has ranged from 5% to 35% and that onset can come within hours of the first dose or months after starting. A two-month delay therefore does not argue against it.

What weakens it. Almost nothing in her presentation. The throat clearing and the morning drip belong more naturally to the second candidate, but they do not exclude the first.

What is still unknown. Whether the cough will stop when the drug does. The same review advises considering an ACE inhibitor as wholly or partly responsible in any patient with chronic cough taking one, whatever the timing (Dicpinigaitis, 2006). That makes stopping the drug both a test and a treatment.

Candidate 2: Upper Airway Cough Syndrome

What raises it. Allergic rhinitis, a sensation of postnasal drip, frequent throat clearing, pale boggy nasal mucosa and a cobblestone posterior pharynx. Together these are the classic findings of upper airway cough syndrome, a frequent explanation when a nonsmoker's persistent cough comes with a clear chest film.

What weakens it. Her rhinitis is seasonal, and the cough has persisted through the summer months, when her nasal symptoms are usually quiet. The cobblestone pattern is also nonspecific and can be seen without any cough at all.

What is still unknown. Whether treating the nose treats the cough. No single finding confirms this diagnosis, so the answer comes from response to treatment.

Candidate 3: Cough-Variant Asthma or Nonasthmatic Eosinophilic Bronchitis

What raises it. A dry cough worse at night in an adult with atopy. Cough can be the only symptom of asthma, and eosinophilic airway inflammation can cause cough with normal spirometry.

What weakens it. No wheeze, no shortness of breath, no exercise or cold-air trigger and a normal lung examination, including forced expiration. None of these excludes a cough-variant picture, but together they lower its likelihood.

What is still unknown. Her spirometry with bronchodilator response and, where available, a fractional exhaled nitric oxide level, which the European Respiratory Society guideline suggests can help identify patients whose cough may respond to inhaled corticosteroids (Morice et al., 2020).

Candidate 4: Reflux-Associated Cough

What raises it. Heartburn twice a week after large evening meals, and a cough worse at night and with talking.

What weakens it. Her reflux symptoms are mild and episodic while the cough is daily. Many people have heartburn without cough.

What is still unknown. Whether reflux is contributing at all. Morice et al. (2020) recommend against treating chronic cough with acid suppression alone when there are no features of peptic acid reflux, so this candidate should not be tested by simply adding a proton pump inhibitor and waiting.

The Ranking, Argued

By likelihood, the order is ACE inhibitor cough first, upper airway cough syndrome second, cough-variant asthma or eosinophilic bronchitis third and reflux fourth. The first two are close. The drug moves to the top not because the throat findings are weak but because it is the one cause that has a clean, cheap test that also cures it, and because the drug could explain the cough on its own even if her nose is contributing.

By danger, the ranking barely changes, and that is worth saying. With a normal chest radiograph, no smoking history, no weight loss and no hemoptysis, none of the four candidates carries a serious short-term risk. The dangerous causes of chronic cough, such as lung cancer, tuberculosis or heart failure, have been made unlikely by the history, the examination and the film. If any red flag appears, that statement changes.

It is also possible that more than one cause is operating. Chronic cough often has several contributors, which is why the plan below tests them one at a time rather than all at once. If three things were changed together, a better week afterward could not be credited to any one of them.

The Discriminating Steps, in Order

Step 1: Replace lisinopril with losartan, 50 mg once a day. Angiotensin receptor blockers do not appear to cause cough more often than the comparison drugs in trials (Dicpinigaitis, 2006), so her blood pressure stays treated. If the cough resolves within four weeks, the first candidate is confirmed. If it improves only partly, the drug was one contributor. Because the cough can take up to three months to settle after the drug is stopped (Dicpinigaitis, 2006), a partial response at four weeks is not a failure of the diagnosis.

Step 2, at four weeks if cough persists: treat the upper airway. A daily intranasal corticosteroid for four weeks. Improvement moves upper airway cough syndrome up; no change moves it down.

Step 3, in parallel or next: spirometry with bronchodilator. Ordered now so the result is ready if steps 1 and 2 fail. A significant bronchodilator response would move the third candidate to the top.

Step 4: reflux only if features appear. If she develops more frequent heartburn or regurgitation, diet timing and a trial of acid suppression can be discussed, with the limits of that approach explained.

Return precautions. She should return sooner for blood in her sputum, fever, weight loss, new shortness of breath or chest pain, any of which would reopen the question of a serious cause.

A Working Conclusion

The working diagnosis is ACE inhibitor cough, with upper airway cough syndrome as a close second and possibly a co-contributor. That conclusion is provisional. I would drop it if the cough is unchanged four weeks after stopping lisinopril, at which point the airway candidates become the leading explanations and the spirometry result decides between them.

References

Dicpinigaitis, P. V. (2006). Angiotensin-converting enzyme inhibitor-induced cough: ACCP evidence-based clinical practice guidelines. Chest, 129(1 Suppl.), 169S-173S. https://doi.org/10.1378/chest.129.1_suppl.169S

Irwin, R. S., French, C. L., Chang, A. B., Altman, K. W., & CHEST Expert Cough Panel. (2018). Classification of cough as a symptom in adults and management algorithms: CHEST guideline and expert panel report. Chest, 153(1), 196-209. https://doi.org/10.1016/j.chest.2017.10.016

Morice, A. H., Millqvist, E., Bieksiene, K., Birring, S. S., Dicpinigaitis, P., Domingo Ribas, C., Hilton Boon, M., Kantar, A., Lai, K., McGarvey, L., Rigau, D., Satia, I., Smith, J., Song, W.-J., Tonia, T., van den Berg, J. W. K., van Manen, M. J. G., & Zacharasiewicz, A. (2020). ERS guidelines on the diagnosis and treatment of chronic cough in adults and children. European Respiratory Journal, 55(1), Article 1901136. https://doi.org/10.1183/13993003.01136-2019