FRIDAY, Jan. 6 (HealthDay News) -- Almost half of patients with
mild or moderate asthma may have a different type of disease than
those with more severe symptoms, perhaps explaining why common
treatments don't work well for them, new research suggests.
"We are beginning to understand that different 'flavors' of asthma probably have different molecular mechanisms," said Dr. John Fahy, director of the Airway Clinical Research Center at the University of California, San Francisco. He is the senior author of the new study, published online Friday in the American Journal of Respiratory and Critical Care
Asthma is a chronic disease involving inflamed airways. As the
airways become more swollen, the muscles around them can tighten
when something triggers symptoms such as coughing, wheezing and
shortness of breath.
Current anti-inflammatory treatments target a condition called
eosinophilic airway inflammation, which is common in asthma.
Eosinophils are a type of white blood cell that help fight off
infection and play a role in the immune response.
However, the new research finds that nearly half of the 995
patients studied did not have this condition.
Fahy's team repeatedly measured these white blood cells in
sputum samples of the volunteers with asthma who were enrolled in
nine clinical trials.
Nearly half, or 47 percent, had no airway eosinophilia on any
test of their sputum. Some had the condition intermittently and
some had it on each test.
The investigators found that only 36 percent of those not taking
an inhaled corticosteroid, an anti-inflammatory, had the condition,
while 17 percent of those who used the inhaled steroids did.
After two weeks of giving the participants anti-inflammatories
and bronchodilator therapy, Fahy found those with the airway
eosinophilia responded and had better airflow. But those who didn't
have the condition did not respond. The responses to the
bronchodilators -- other medicines commonly used for asthma that
work by helping to open the bronchial tubes -- were similar in both
Previous studies looked at a single sample to assess whether
those with asthma had the white blood cell involvement, Fahy
explained, while this study looked at many over time.
"This study reinforces the idea that asthma is not a one-type disease," he said.
Even within the nearly 50 percent without the white blood cell
involvement, there are probably many different subtypes, Fahy
The test used was a complicated research test, Fahy pointed out,
and it is not easily done in clinical practice.
Based on the study results, researchers might next work on a
simpler test to determine if those with asthma have involvement of
these white blood cells, he said. Eventually, the findings may help
doctors better individualize asthma treatment.
The findings suggest that a sizeable group of people with mild
to moderate asthma have a type of disease that is not typical, with
poorly understood mechanisms, and that new treatments will be
needed, Fahy concluded.
"The finding that half of these had the absence of eosinophils in the sputum was a little surprising," said Dr. Len Horovitz, a pulmonary specialist at Lenox Hill Hospital in New York City.
"It's higher than I thought," Horovitz said. The "cascade" of inflammation in asthma -- what happens to bring on the symptoms -- has been well studied, he noted. However, "we can't guarantee that our current regimen of bronchodilators plus inhaled corticosteroids is going to work, even in mild asthma," Horovitz explained.
Doctors should ask their patients with asthma if they produce a
lot of sputum, Horovitz suggested. If they do, they tend to respond
to the corticosteroids.
To learn more about asthma, visit the
American Academy of Allergy, Asthma and
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