In this entry, I would like to comment on how the fact that asthma is such a common disease can in some cases lead to individuals being told they have "asthma," yet on detailed review with specialized tests, are found not to have asthma. I know that this can sound a little confusing: "My doctor told me I have asthma and I am taking asthma medicines." So what's up?
Common symptoms, common diagnosis
I recently heard from a friend about his wife's difficulty with her asthma. Since she had a bad cold late in the fall, she has been needing nebulizers on a daily basis. Apart from a little exercise and cold-induced asthma when she was younger, she had not had any breathing difficulties until recently. She also hadn't felt much better during a course of prednisone (a steroid pill) -- this is unusual for a person with asthma. I set her up to see me in clinic on my next available slot. Even though she was still feeling some shortness of breath, she did not report any wheeze, and her breathing tests in clinic were normal. While we will figure out what she has with further tests, her current symptoms are probably not caused by her asthma.
My point is that asthma affects many people (about 6% of the US population), and shortness of breath is a very common symptom. When a patient reports wheeze or chest tightness along with shortness of breath, it is not unreasonable to consider asthma as the cause and start treating. This may not always be correct -- beyond similar anecdotal experiences in my clinic in which people were referred to me as an asthma specialist to help a patient with difficult to control asthma, yet ended up not having asthma, there is some very recent research in this area. An asthma diagnosis may be incorrect up to 30% of the time, according to a recent study.
Is asthma more commonly misdiagnosed in obese individuals?... and a more interesting finding from the study
Asthma is known to be more common in obese individuals, but is the diagnosis of asthma made more commonly in obese people simply because they are more commonly short of breath? A recent moderate-sized study was recently carried out in Canada to ask the question if asthma was more often misdiagnosed in people who were clinically obese - defined as a body mass index (BMI) of >30. (I reviewed the topic of obesity and asthma in June 2006 for readers, in which I define BMI calculation; this topic has been discussed by our other experts, including Nancy Sanker, as well as several other pages about this on our website).
After recruiting patients with a physician diagnosis of asthma, a series of detailed steps and tests were undertaken to either confirm or refute their asthma diagnosis. In terms of the study objective, there was a marginally higher rate of asthma misdiagnosis in the obese participants. Of note, this difference was not ‘statistically significant' (which means that this difference was very likely due to chance alone, not a ‘real' difference). More interestingly, using a rigorous standard for diagnosing (or excluding) asthma, nearly a third (30.3%, to be exact) of patients with self-reported and doctor-diagnosed asthma were found not to have asthma. Once this was figured out, the majority of these patients was successfully taken off of asthma medications and did not seek further health care for asthma symptoms.