One third of adults with asthma may be misdiagnosed

You go to your family doctor complaining of difficulty breathing, wheezing, tightness in your chest, and a cough. Your doctor listens to your chest, makes some notes and diagnoses you with asthma. You get some inhalers to control the symptoms and carry on your way. Surprisingly, there was never a test done to determine if you in fact had asthma. In diseases like diabetes, a diagnosis is only given once a blood glucose test has been returned as positive. Asthma comes in many different forms and therefore can be difficult to diagnose without such a test. Since many diagnoses of asthma are given based on observations, it would not be unreasonable to think that some people diagnosed with asthma in fact do not have the disease. There are many things that could cause asthma like symptoms and so without an objective test it may be difficult to determine whether a disease is in fact asthma. In a recent paper published by a research team from across Canada set out to determine how many people recently diagnosed with asthma were misdiagnosed.

The study had 613 people come in and complete the asthma testing to confirm or refute their diagnosis. The guidelines for confirmation were rigorous to say the least. Patients underwent spirometry to test how well their lungs were working. In this test, they measured the amount of air people could expire from their lungs in 1 second and then gave them an inhaler to open their airways and did the test again. If the person’s lung function improved by 12% or more they were confirmed to have asthma and removed from the study. 86 people had confirmed asthma by this test. Next, the remaining patients were subjected to a bronchial challenge test in which they inhaled a drug (methacholine) which causes airways to narrow. By measuring the dose at which the person’s airways began to narrow they could tell how sensitive to the drug they were. If you were sensitive to 8mg/mL or less, then you were determined to have asthma. Anyone who passed this test (ie. Didn’t have asthma) had their medications halved and were retested in 3 weeks. After the second test, people who still passed (didn’t have asthma) were asked to stop their medications altogether and undergo the test again. At the end of these 3 bronchial challenge tests, 287 people were confirmed to have asthma. The remaining people were monitored for the next year and gradually had their medications tapered off. Those that got worse during the medication tapering were determined to have asthma (9 people). In some cases, the pulmonologist on the study diagnosed people with asthma during this tapering period and were put back on their medication. In this case the patients were considered to have asthma (28 people).

After all that testing, 203 people out of 613 (33.1%) did not have asthma by all the empirical measurements available during this study. Many of them had other diseases that presented like asthma but upon testing could be ruled out as asthma. Some of these diseases included: COPD, anxiety, obesity, or cough post viral infection. This study highlights the need for empirical testing of asthma to confidently confirm the diagnosis. There is no need to give asthma drugs to someone who does not have asthma especially when they should be receiving different care. The test for asthma (spirometry or bronchial challenge test) is not difficult to perform and can be tracked over time for a greater confidence in the diagnosis. Hopefully this type of a paper will help shape our how asthma is diagnosed in our health care system in order to get the medication and to those who actually need it.

Image Credit: Flickr NIAID

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