Doctors wouldn’t put a cast on a leg they thought was broken without an x-ray. Nor would they diagnose diabetes and start a patient on insulin without ordering a blood test, or at least a urine analysis. But too frequently doctors diagnose asthma without doing the standard test of lung function — spirometry.
These findings of a recent Canadian study mean that people who have not been tested may be misdiagnosed with asthma when they may have another serious cardiopulmonary condition such as ischemic heart disease. Or they may have nothing seriously wrong at all.
Asthma medication can be expensive and may have side effects, and misdiagnosis of asthma can result in people taking medications they do not need, Shawn Aaron, lead author of the study, told TheDoctor. Eighty-eight percent of participants in the study who did not have asthma took medication for it, and 35 percent took it daily.
“If you are taking asthma medicine and are asymptomatic, you may want to ask your physician about taking a spirometry test and adjusting your medicine.”
“I was surprised that a third of people in our study who were initially diagnosed with asthma didn’t have active asthma. We think for some, their asthma went into remission, while others were misdiagnosed,” said Aaron.
Then researchers looked at the health records of 530 of the study participants to see how they were initially diagnosed with asthma. Forty-nine percent of these patients had been diagnosed with asthma based on symptoms and/or physical findings alone.
When the patients who did not have asthma were re-diagnosed, some were found to have conditions such as allergies or heartburn. And 28 percent had nothing wrong.
Spirometry testing is inconvenient, and this is likely one reason physicians may not order it, Aaron explained. “The patient has to go to another facility to take the test, then go back to the doctor for the results and any medications if necessary,” he said. So spirometry testing potentially involves two extra appointments for the patient.
In his practice he sees people whose asthma has literally gone into remission — they are taking asthma medicine and have no symptoms. “If you are taking asthma medicine and are asymptomatic, you may want to ask your physician about taking a spirometry test and adjusting your medicine,” Aaron said. You may be able to reduce the dose you are taking.