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How is adult-onset asthma diagnosed?
Your asthma doctor may diagnose adult-onset asthma by:
Taking a medical history, asking about symptoms, and listening to you
Performing a lung function test, using a device called a spirometer to
measure how much air you can exhale after first taking a deep breath. The
device also measures how fast you can empty your lungs. You may be asked at
some time before or after the test to inhale a short-acting bronchodilator
(medicine that opens the airways by relaxing tight muscles and that also help
clear mucus from the lungs).
Performing a methacholine challenge test. This asthma test may be performed
if your symptoms and spirometry test do not clearly show asthma. When inhaled,
methacholine causes the airways to spasm and narrow if asthma is present.
During this test, you inhale increasing amounts of methacholine aerosol mist
before and after spirometry. The methacholine test is considered positive,
meaning asthma is present, if the lung function drops by at least 20%. A
bronchodilator is always given at the end of the test to reverse the effects of
Performing a chest X-ray. An X-ray is an image of the body that is created
by using low doses of radiation reflected on special film or a fluorescent
screen. X-rays can be used to diagnose a wide range of conditions, from
bronchitis to a broken bone. Your doctor might perform an X-ray exam on you in
order to see the structures inside your chest, including the heart, lungs, and
bones. By viewing your lungs, your doctor can see if you have a condition other
than asthma that may account for your symptoms. Although there may be
signs on an X-ray that suggest asthma, a person with asthma will often have a
normal chest X-ray.