TUESDAY, Jan. 17, 2017 (HealthDay News) -- Many adults who've been diagnosed with asthma may not actually have the respiratory disease, a new study suggests.
Researchers in Canada said that of more than 600 adults diagnosed with asthma, one-third did not have the disease based on objective tests.
Eighty percent of those people had been taking asthma drugs. That included 35 percent who were taking medication every day, the investigators found.
Respiratory experts said the findings are worrying, considering the cost and side effects of asthma drugs.
And it's not completely clear why so many patients with an asthma diagnosis did not really have the disease.
There were some cases where people obviously had asthma when they were diagnosed, said lead researcher Dr. Shawn Aaron, a respiratory specialist at Ottawa Hospital, in Canada. But their symptoms later went into remission.
In most cases, though, it could not be determined whether the patient's asthma had gone away or been misdiagnosed from the start, Aaron said.
What was clear, he said, is that many patients were told they had asthma without any objective testing.
Almost half had been diagnosed based only on their symptoms and their doctor's evaluation.
And that's a problem, according to Aaron. He said it's "bizarre" that doctors would diagnose a chronic disease without the available objective tests.
"If someone had possible symptoms of diabetes, a doctor wouldn't say, 'Oh, you have diabetes, here's some insulin,'" Aaron said. "They would order a test of the patient's blood sugar levels."
To help diagnose asthma, doctors use a spirometer -- a device that measures how well a patient can inhale and exhale.
Aaron could not say why so many doctors may be skipping spirometry. (Primary care doctors can do it themselves, without referring patients to a specialist, he noted.)
But Aaron speculated that some doctors might not be comfortable with spirometry. "Some primary care providers may feel they don't have the expertise, or the time, to do it," he suggested.
Whatever the reasons, doctors should be testing before giving a diagnosis, according to a respiratory expert who was not involved in the study.
"This study underscores the possibility of over-diagnosis of asthma, and the importance of careful testing of pulmonary [lung] function to make a clear diagnosis before committing a patient to lifelong treatment," said Dr. Brian Christman, a spokesman for the American Lung Association.
Even after a careful diagnosis, the patient's treatment can be re-evaluated over time, said Christman, who is also a professor of medicine at Vanderbilt University, in Nashville, Tenn.
If the asthma is well-controlled for some time, doctors can lower the "intensity" of the medication regimen, Christman added.
In fact, Aaron pointed out, guidelines suggest that patients have their treatment "stepped down" if their symptoms have been under good control for three months.
The new findings, published in the Jan. 17 issue of the Journal of the American Medical Association, are not completely unexpected.
Past studies had hinted that many adults with an asthma diagnosis might not really have the disease. But the current study was more rigorously done, Aaron said.
His team recruited 701 Canadian adults who'd been diagnosed with asthma within the past five years. The researchers analyzed the patients' medical records and gave them a series of breathing tests.
In the end, asthma was ruled out in one-third of the patients.
So what was wrong with them? Many people -- almost 29 percent -- had no medical condition, while roughly one-third had symptoms that were traced to allergies or heartburn.
A small number of people had serious medical conditions that were misdiagnosed as asthma, Aaron said: 2 percent had conditions such as heart disease and chronic lung diseases other than asthma.
Among all patients who had asthma ruled out, over 90 percent were able to stop their medications for one year with no problems, the findings showed.
Symptoms like coughing and wheezing are not enough to make an asthma diagnosis, Christman stressed. Those problems, he said, can also be signs of heart failure or interstitial lung disease, for example.
Aaron had this advice: If your doctor says you have asthma, ask for a spirometry test to confirm it.
"If you insist on the right testing," he said, "you'll get it."
The same goes for adults who think they've been misdiagnosed with asthma, or believe their asthma has remitted, he said.
"Do work with your doctor," Aaron advised. "I wouldn't want people to stop or taper their asthma medication on their own. Uncontrolled asthma can be deadly."
The U.S. National Institutes of Health has more on diagnosing asthma.