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Shortness of breath. Wheezing. Coughing. Chest tightness. If you had asthma, you'd know it, right? It turns out that it's not always that simple, and even your doctor can get it wrong. When Canadian researchers studied more than 700 people who had been diagnosed with asthma in the past five years, they determined that one-third of them didn't have asthma after all. Their study, published in JAMA, suggests that you might very well be treating a condition you don't even have—while simultaneously neglecting your real issue.

How could this happen? Lead study author Dr Shawn Aaron, a senior scientist at the Ottawa Hospital Research Institute, suspects that doctors are often relying on symptoms to make a diagnosis, but "asthma" symptoms can overlap with those caused by other health problems. He says that physicians ought to be conducting an objective spirometry test, but some are skipping this step.

The test is simple—you blow into a tube, and the doctor measures how quickly you blow the air out—but only half of the patients in Aaron's study were given one. "We think that doctors are taking shortcuts," he says. "Although we can't say exactly how many were misdiagnosed initially verses how many went into remission, we think a sizable proportion were misdiagnosed from the beginning."

If you've been told you have asthma but haven't had a spirometry test, see an asthma/immunology specialist to get tested now. "You wouldn't let a physician give you insulin to treat diabetes without testing your blood sugar," says Aaron. "Patients are accepting inhalers for asthma all the time without getting appropriate testing to confirm."

If it turns out asthma isn't actually what's making you cough and wheeze, it's time to do a little detective work. You might have one of the following conditions instead.