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NEW YORK (Reuters Health) - Some obese adults may be at increased risk of having their breathing difficulties misdiagnosed as asthma, a new study suggests.Researchers found that among nearly 500 Canadian adults who said a doctor had diagnosed them with asthma, objective lung-function testing ruled out the lung disease in 150, or 30 percent. When the investigators looked at risk factors for misdiagnosis, obesity in general did not play a clear role. However, among patients who had sought emergency care for breathing problems in the past year, obese men and women were four times as likely as their normal-weight counterparts to be misdiagnosed with asthma. The study, reported in the journal Chest, could not ascertain the reasons for patients' misdiagnoses or for the higher risk among obese adults who sought urgent care.But past research has indicated that spirometry, a standard test of lung function, is not used as often as it should be in diagnosing asthma, said Dr. Smita Pakhale of the Ottawa Hospital in Ontario, Canada, who led the new study. Asthma should be diagnosed based on both symptoms and lung-function testing, and underuse of the latter could be a factor in some of the incorrect diagnoses in this study, Pakhale told Reuters Health -- though, she added, that is just speculation.Pakhale also pointed out that obese adults are at heightened risk of a number of health problems that could cause asthma-like symptoms such as breathlessness and chest tightness. Those include low fitness levels, acid reflux and heart disease.Pakhale said that people who are told they have asthma after seeking care at an emergency room or walk-in clinic should be sure to follow up with their primary care doctor. That way, she said, they can get any additional evaluation or testing that may be needed -- which may uncover the actual cause of the symptoms, if it is not asthma.The study included 496 randomly selected adults from eight Canadian cities who said a doctor had diagnosed them with asthma. Roughly half were obese and the rest were normal-weight.Overall, lung function testing confirmed the asthma diagnosis in 70 percent of study participants. Of these men and women, 14 percent and 15 percent of obese and normal-weight people, respectively, had sought emergency care for breathing problems in the past year. Of study participants who turned out not to have asthma, 21 percent of obese individuals had sought urgent treatment for respiratory symptoms in the past year. That figure was less than 10 percent among normal-weight men and women. When Pakhale's team considered other factors, including socioeconomics, obese study participants who needed emergency care were four times more likely to have been misdiagnosed with asthma as their thinner counterparts.The researchers also found that the time since diagnosis mattered: study participants who had been diagnosed in the past few years had a higher likelihood of misdiagnosis than those who had been told they had asthma "many" years ago. It's possible, Pakhale speculated, that increased asthma awareness among the general public and doctors -- possibly via the recent proliferation of asthma-medication ads -- could have something to do with that finding.