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Asthma Breath Test Useful for Chronic Cough

It helps predict whether certain drugs can ease the condition, researchers say

WEDNESDAY, Sept. 6, 2006 (HealthDay News) -- An easy, quick and inexpensive breath test can help determine whether inhaled corticosteroids can treat a patient's chronic cough, a Mayo Clinic team reports.

Chronic cough refers to coughing that lasts a few weeks or longer. The condition, which can disrupt a person's daily life, has three main causes: postnasal drip syndrome; asthma; and gastroesophageal reflux. A less common cause is non-asthmatic eosinophilic bronchitis.

The study of 114 patients evaluated for chronic cough concluded that a test commonly used for asthmatics --- called the exhaled nitric oxide test -- is much easier for patients and predicts response to corticosteroid treatment better than another commonly used test, called the methacholine challenge.

"We're thinking this could be a significant development in the field of chronic cough," study lead investigator and Mayo Clinic pulmonologist Dr. Peter Hahn said in a prepared statement.

"It could drastically change what we do for patients with chronic cough and also the guidelines for diagnosis and treatment of chronic cough. This very accurate -- but rather underused -- test could be used up front for all patients complaining of chronic cough, saving significant time and expense in other testing," he said. "It helps us get to the treatment and bring relief to the patient in the least invasive, fastest way possible."

The exhaled nitric oxide test measures inflammation in the lungs' bronchial tubes. The patient breathes into the analyzer four or five times over 10 minutes. Abnormal scores indicate either asthma or possibly non-asthmatic eosinophilic bronchitis.

In patients with these conditions, inflammation irritates the airway and triggers coughing. Corticosteroids help reduce inflammation and ease this chronic cough.

"Patients with a positive, or abnormal, exhaled nitric oxide test had a strong likelihood of response to inhaled corticosteroids, whereas a negative, or normal, exhaled nitric oxide test virtually excluded response to the medication," Hahn said. Use of the test "may potentially have a significant impact on how patients with chronic cough are evaluated and treated," he said.

The findings were expected to be presented Sept. 6 at the European Respiratory Society Meeting in Munich, Germany.

More information

The American Academy of Family Physicians has more about chronic cough.

SOURCE: Mayo Clinic, news release, Sept. 6, 2006
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