Asthma is incredibly common, with around 1 in 13 adults suffering from the condition that causes coughing fits and shortness of breath, according to the Centers for Disease Control and Prevention. But a full third of those cases might be misdiagnosed, according to a new study in the Journal of the American Medical Association.
Researchers re-examined 613 adults who had been diagnosed with asthma in the past 5 years, and found that 203 of the patients didn't actually have asthma, after all. Instead, what looked like asthma—chest tightness, trouble breathing, and coughing—turned out to be caused by allergies, acid reflux, or nearly two dozen other ailments. And 61 of those people weren't even showing asthma symptoms anymore.
"I was being referred a lot of patients with diagnoses of asthma," says study author Shawn Aaron, the director of respirology at the University of Ottawa. "When I would assess them, I came to realize that there was a minority of these patients who don't have asthma and never had asthma, but were being treated for asthma."
There are a few reasons why you wouldn't want to take asthma medications when you don't need them. Bronchodilators, which open airways to let asthma sufferers breathe comfortably, can cause tremors and anxiety—kind of like the feeling you get after slamming a few cups of coffee. Inhaled steroids, which treat the inflammation in your airways from asthma, can cause a fungal infection in the mouth, glaucoma, or osteoporosis.
Before you panic if you're taking either of those types of meds, Aaron points out: "Those side effects can be trivial compared to the effects of uncontrolled asthma." But if you're in that 33 percent that don't have the condition, you're taking risks with those inhalers for no reason.
At the same time, an asthma misdiagnosis could be masking something worse. Four patients in the study actually had serious cases of heart disease, four had chronic obstructive pulmonary disease (COPD), and two more had to have surgery to remove a buildup of scar tissue in their throat.
Most of the doctors who had mistakenly labeled a patient's condition as asthma did so without ordering a standard spirometry test. That's when patients blow into a tube to measure their lung strength, and then doctors give them four puffs of a bronchodilator to see if they can do any better on the second try. If bronchodilators help, the test confirms asthma.
Yet in roughly half the cases—and only a bit more often when the asthma diagnosis was correct—doctors didn't order the "gold standard" diagnostic test. "It's the equivalent of diagnosing diabetes without a blood sugar test, or casting a broken bone without an X-ray," Aaron says.
The problem isn't that the test is expensive: In Canada, it only costs $20. Even the United States' inflated medical costs only bring the test to between $40 and $80. Instead, Aaron said, it's simply a matter of convenience. Performing the test usually means going to a lab, which might not be far—especially in a hospital—and waiting for the test results takes time out of a physician's busy schedule. It may not sound like much of a hassle, but with asthma already common, those hurdles were apparently enough of a burden for most doctors to feel like the test wasn't worth the trouble.
Although Canada's single-payer medical system functions differently from the U.S., Aaron said it's likely that the problem of overdiagnosing asthma is as common in most Western countries. Similar results have been found in studies in the Netherlands and Italy.
Fortunately, you can always ask your doctor for a spirometry test, especially if you're being diagnosed for the first time with asthma, COPD, or emphysema. "As a patient, you should not accept these diagnoses without doing the test," Aaron says.