Tests to Diagnose Asthma
There is no single test for asthma.
To properly diagnose
doctor will ask you or your child several questions about symptoms, medical
history, and risk factors. They will also perform a physical exam to rule out
any other possible conditions. A number of diagnostic tests are available to
help diagnose asthma.
Spirometry is a lung function test
that measures how much air you can inhale and exhale in one second.
Below-normal results can indicate airway obstruction. Your doctor may then give
you medication and repeat the test to see whether there is improvement.
Bronchial Challenge Test
During a bronchial challenge test, a
known asthma trigger is inhaled to cause the airways to constrict. A spirometer
is then used to measure the subsequent lung function. If you react to the
trigger to a certain level of sensitivity, you likely have asthma. This test is
also called a methacholine challenge test or a histamine challenge test.
A peak flow meter can determine your
peak expiratory flow rate (PEFR), a measure of lung function. This is often a
self-administered test for monitoring asthma. The peak flow meter is
easy to use at
High levels of nitric oxide in your
breath could mean that your airways are inflamed, which is a common sign of
asthma. The nitric oxide test involves blowing into a mouthpiece connected to a
machine. It measures the amount of nitric oxide in your breath.
A chest X-ray will allow your doctor
to see inside your chest and examine your lungs radiographically. While it may
not enable a specific diagnosis of asthma, it may help rule out other factors
that might be affecting your breathing. This could be something like a broken
bone, an obstruction, or conditions such as pneumonia or bronchitis.