Asthma Test for Chronic Cough
Test Could Help Doctors Better Treat Chronic Cough
Sept. 6, 2006 -- An asthma test may change the way doctors evaluate and
treat chronic cough.
Researchers at the Mayo Clinic today reported that a test called the exhaled
nitric oxide test, commonly used for asthma patients, can help predict which
chronic cough patients would be helped by inhaled corticosteroids.
In the exhaled nitric oxide test, the patient breathes into a device four or
five times over 10 minutes. The device then measures nitric oxide in the
patient's exhaled air.
The test isn't new. Currently, it is used to look for inflammation of the
airways, a symptom of asthma.
But the test may also help evaluate and guide treatment of chronic cough,
which is a cough that lasts more than eight weeks, note Peter Hahn, MD, and
colleagues at the Mayo Clinic in Rochester, Minn.
Hahn's team presented promising results for the exhaled nitric oxide test
today at the 16th European Respiratory Society Congress, held in Munich,
'Drastic Change' Ahead?
"We're thinking this could be a significant development in the field of
chronic cough," Hahn says, in a Mayo Clinic news release.
"It could drastically change what we do for patients with chronic cough
and also the guidelines for diagnosis and treatment of chronic cough," he
Chronic cough is usually due to asthma, postnasal drip, or gastroesophageal
reflux (GERD), the
researchers note. A less common cause is eosinophilic bronchitis.
Asthma and eosinophilic bronchitis can be treated with inhaled
corticosteroids, which combat inflammation in the airways to reduce asthma
In their study, Hahn's team reviewed the medical charts of 114 chronic cough
patients seen at the Mayo Clinic.
The patients had taken the exhaled nitric oxide test. They had also
performed methacholine challenge testing, in which patients inhale a chemical
called methacholine as part of a lung function test.
Of those two tests, the exhaled nitric oxide test was better at predicting
which chronic cough patients would be helped by inhaled corticosteroids, the
A total of 47 patients had high levels of exhaled nitric oxide. Of those
patients, 41 started using inhaled corticosteroids, and 36 noted improvement in
Another 65 patients had normal levels of exhaled nitric oxide. Twenty-three
began using inhaled corticosteroids. But only two of those patients reported
cough improvement, the researchers write.
In short, inhaled corticosteroids were only likely to help ease chronic
cough in patients with high levels of exhaled nitric oxide.
Methacholine challenge testing wasn't as specific at predicting which
patients would be helped by steroid treatment, the study shows.
The exhaled nitric oxide test is "very accurate but rather
underused," Hahn says.
He adds that the test "could be used up front for all patients
complaining of chronic cough, saving significant time and expense in other
"It helps us get to the treatment and bring relief to the patient in the
least invasive, fastest way possible," Hahn says.
Hahn calls for further studies of the exhaled nitric oxide test in patients
with chronic cough.