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What is the best approach to the evaluation and treatment of chronic cough?

EVIDENCE-BASED ANSWER

Potentially cough-inducing agents, such as tobacco products and angiotensin-converting enzyme (ACE) inhibitors, should be eliminated first. Evaluation and treatment for postnasal drip syndrome (PNDS), asthma, and gastroesophageal reflux disease (GERD) should remedy symptoms in the vast majority of patients (grade of recommendation: C, based on case series at referral centers).

EVIDENCE SUMMARY

By definition, chronic cough persists past 3 to 8 weeks.[1] Irwin proposed an algorithm to evaluate chronic cough in 1981[2] that has successfully diagnosed and treated chronic cough 82% to 100% of the time in referral centers.[2-6] Among patients in this setting who are not using tobacco or ACE inhibitors (assuming a normal or stable chest x-ray), most have PNDS, asthma, GERD, or a combination of these diagnoses.[2-5] The protocol evaluates for these 3 conditions. The key weakness of the protocol is that a positive diagnostic test result does not mean that treatment for that condition will relieve the cough.[5] Recently, empiric treatment before diagnostic testing has been recommended for primary care.[1]

An important unanswered clinical question is whether empiric treatment trials or diagnostic testing-directed trials are the best approach.[7] Initial empiric treatment for PNDS appears reasonable, since it is the most common single cause of chronic cough,[2,4-6] and symptoms and signs and diagnostic tests for PNDS are unreliable.[3,6] One prospective study using empiric PNDS treatment as a first step decreased the number of tests required and the mean time to diagnosis compared with previously published studies.[6] No studies were found evaluating empiric treatment for asthma before diagnosis. Multiple studies report a 100% negative predictive value for the methacholine challenge test,[3-5] but this carries some risk and is not universally available. Empiric treatment of GERD with omeprazole before diagnostic testing with a 24-hour pH probe was evaluated in 1 study. Cough resolved with treatment in only 6 of 17 patients with a positive 24-hour pH probe.[8] In another study, 5 of 5 patients with cough due to GERD responded to an [H.sub.2]-blocker.[6] The negative predictive value of a 24-hour pH probe is between 90% and 100%,[3-6] but this may also be reserved for those who fail initial empiric therapy.

The best timing of the chest x-ray is also unclear. The diagnostic protocol has been historically evaluated in patients with a normal or stable chest x-ray.[2-5] One study used a protocol that delayed the chest x-ray for 2 weeks, until after empiric treatment for PNDS and evaluation for asthma. These authors eliminated half of the x-rays and achieved results equivalent to previous studies.[6]

A recommended approach based on available literature is outlined in the Table. Keep in mind that all studies have been done in referral centers.
TABLE
EVIDENCE-BASED APPROACH TO THE CHRONIC COUGH

1. Perform a history and physical examination, treating suspected cause
or reassuring patient if recently recovering from a respiratory
infection.

2. Stop angiotensin-converting enzyme inhibitor or tobacco use.

3. Treat empirically for postnasal drip syndrome (PNDS) for 1 to 2
weeks with a first-generation antihistamine-decongestant combination.
Continue therapy while performing further evaluation.

4. Treat empirically for asthma for evaluate with a methacholine
challenge test and treat, if positive). If cough resolves, consider
discontinuing PNDS therapy. If cough persists, continue therapy during
further evaluation.

5. Obtain a chest x-ray (consider earlier with advancing age or history
of smoking).

6. Treat empirically for gastroesophageal reflux disease (or evaluate
with a 24-hour pH probe, and treat if positive). If cough resolves,
consider discontinuing PNDS and asthma therapy in a stepwise fashion.

7. Re-evaluate effectiveness of PNDS, asthma, and GERD therapy.

8. Consider referral.


RECOMMENDATIONS FROM OTHERS

The American College of Chest Physicians recommends the following order of interventions: stop ACE inhibitors, obtain chest x-ray, avoid irritants (such as tobacco), evaluate for PNDS, evaluate for asthma, evaluate for GERD, consider special studies, and reconsider adequacy of treatments.[9]
Heidi Chumley Jones, MD
University of Texas, San Antonio


CLINICAL COMMENTARY

Chronic cough is an extremely common and vexing problem in primary care. The approach recommended above is helpful and sensible, and I offer a few comments. Given the 3- to 8-week minimum definition of chronic cough, many patients who present with "chronic" cough to their primary care provider will have a postviral cough that will go away on its own. This includes patients taking ACE inhibitors, and how long they are allowed to cough before you stop the ACE inhibitor is a difficult question. Also, before blaming a new "chronic" cough on tobacco use, remember that smokers get reflux, postnasal drip, and asthma at least as often as nonsmokers, not to mention lung cancer. Finally, methacholine challenge testing and pH probe testing are not readily available in my public institution, but even where they are available, I think empiric treatment is more cost-effective and more acceptable to patients.
Sang-Ick Chang, MD
San Francisco, California


REFERENCES

[1.] Lawler R. An office approach to the diagnosis of chronic cough. Am Fam Physician 1998; 58:2015-22.

[2.] Irwin RS, Corrao WM, Pratter MR. Chronic persistent cough in the adult: the spectrum and frequency of causes and successful outcomes of specific therapy. Am Review Respir Dis 1981; 123:413-17.

[3.] McGarvey LP, Heaney LG, Lawson JT, et al. Evaluation and outcomes of patients with chronic non-productive cough using a comprehensive diagnostic protocol. Thorax 1998; 53:738-43.

[4.] Smyrnios NA, Irwin RS, Curley FJ, French CL. From a prospective study of chronic cough: diagnostic and therapeutic aspects in older adults. Arch Intern Med 1998; 158:1222-28.

[5.] Irwin RS, Curley FJ, French CL. Chronic cough: the spectrum and frequency of causes and key components of the diagnostic evaluation and outcomes of specific therapy. Am Rev Respir Dis 1990; 141:640-47.

[6.] Pratter MR, Bartter T, Akers S, Dubois J. An algorithmic approach to chronic cough. Ann Intern Med 1993; 119:977-83.

[7.] Irwin RS, Madison JM. Symptom research on chronic cough: a historical perspective. Ann Intern Med 2001; 134:809-14.

[8.] Ours TM, Kavauru MS, Schultz RJ, Richter JE. A prospective evaluation of esophageal testing and a double-blind randomized study of omeprazole in a diagnostic and therapeutic algorithm for chronic cough. Am J Gastroenterol 1999; 94:3131-38.

[9.] American College of Chest Physicians. Managing cough as a defense mechanism and as a symptom. Figures accessed at: www.chestnet.org/health.science.policy/quick.reference.guides/ coughqrg.figures.html.
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Author:Jones, Heide Chumley; Chang, Sang-Ick
Publication:Journal of Family Practice
Geographic Code:1USA
Date:Sep 1, 2001
Words:1066
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