Adult With New Asthma? Maybe Not
Misdiagnosis occurs about a third of the time, study finds

(HealthDay News) -- Adults diagnosed with asthma just might not have the disease after all.

Asthma generally develops in childhood, but some people do develop the chronic lung disease as an adult. However, research now suggests that as many as one in three adults diagnosed with asthma do not actually have the disease.

"When we evaluated these people with lung function tests and then took them off their medications, we couldn't find asthma in 29 percent of the non-obese and 32 percent of the obese," Dr. Shawn Aaron, a senior scientist in clinical epidemiology at the Ottawa Health Research Institute at the University of Ottawa and a co-author of the study, told HealthDay.

Why the misdiagnosis?

Some of the people might have had viral infections that caused lasting respiratory symptoms, Aaron said. Symptoms, such as wheezing or coughing, can sometimes last as long as several months after an infection has cleared.

But the primary reason, he said, is that doctors don't always perform the lung function tests that are key to properly diagnosing asthma.

Dr. Jennifer Appleyard, chief of allergy and immunology at St. John Hospital in Detroit, agreed. "You need to have some objective measure," she told HealthDay. "You can't diagnose asthma based on patient symptoms alone."

About 15 million people in the United States have asthma, according to the Asthma and Allergy Foundation of America. Symptoms of the disease include wheezing, coughing and shortness of breath. Women are more likely than men to be diagnosed with asthma after age 20, and people who are overweight are more apt to receive an asthma diagnosis later in life, according to the foundation.

Aaron's study, which was published in the Canadian Medical Association Journal, included almost 500 Canadian adults who had been diagnosed with adult-onset asthma. About half of the participants were considered obese.

All of them were given a lung function test, called spirometry. If they did well on the lung function test, they were also given an airway "challenge" test. Someone with asthma generally won't do well on the challenge test, he said.

If participants passed both the lung function test and the challenge test, they were tapered off their asthma medications, something that Aaron advises should be done only under a doctor's supervision.

The researchers found that asthma had been misdiagnosed in 32 percent of the obese study participants and 29 percent of those who were not obese. Six months later, only 8 percent had experienced symptoms that prompted them to seek health care.

Although Aaron's study focused on Canadian adults, Appleyard said that misdiagnosis of asthma is a problem in the United States as well.

In addition to mistaking lingering viral illness for asthma, she said, other diseases sometimes misdiagnosed as asthma are chronic obstructive pulmonary disease, such as emphysema, and congestive heart failure.

Both doctors said that including spirometry as part of the diagnosis should cut down on the number of people misdiagnosed. Doctors who don't have a spirometry machine, they said, should refer patients to someone who does.

On the Web

To learn more about how asthma is diagnosed, visit the U.S. National Heart, Lung and Blood Institute.

SOURCES: HealthDay News ; Shawn Aaron, M.D., senior scientist, clinical epidemiology, and associate professor, medicine, Ottawa Health Research Institute, University of Ottawa, Canada; Jennifer Appleyard, M.D., chief, allergy and immunology, St. John Hospital, Detroit; Nov. 18, 2008, Canadian Medical Association Journal; Asthma and Allergy Foundation of America (www.aafa.org)
Author: Serena Gordon
Publication Date: Nov. 30, 2009
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