Exams and Tests
A diagnosis of
asthma is based on your
medical history, a
physical exam, and lung function tests. If you
developed asthma in adulthood, your doctor will ask about your job to determine
whether you have
occupational asthma.
Lung function tests can diagnose asthma, determine its
severity, and check for complications.
- Spirometry is the most common test used
to diagnose asthma. It measures how quickly you can move air in and out of your
lungs and how much air is moved. The test helps your doctor decide whether
airflow is decreased because of
inflammation in the bronchial tubes and whether the
tubes can return to their usual size in a short time after using medicine.
Doctors also recommend the test at least every 1 to 2 years after asthma
treatment has begun.
- Testing of daytime changes in
peak expiratory flow (PEF) is done over 1 to 2 weeks.
This test is needed when you have symptoms off and on but have normal
spirometry test results.
- An
exercise or inhalation challenge may be used if the
spirometry test results have been normal or near normal but asthma is still
suspected. These tests measure how quickly you can breathe in and out after
exercise or after using a medicine. An inhalation challenge also may be done
using a specific irritant or
allergen if your doctor suspects occupational
asthma.
Regular checkups
You need to
monitor your condition and have regular checkups to
keep asthma under control and to review and possibly update your
asthma action plan. Checkups are recommended every 1
to 6 months, depending on how well your asthma is controlled.
During checkups, your doctor will ask whether your symptoms and
peak expiratory flow have held steady, improved, or
become worse and will ask about asthma attacks during exercise or at night. You
track this information in an
asthma diary. You may be asked to bring your
peak expiratory flow meter to an appointment so your
doctor can see how you use it. Based on the results, your asthma category may
change, and your doctor may change the medicines you use or how much medicine
you use.
Tests for other diseases
Asthma sometimes is hard
to diagnose because symptoms vary widely from person to person and within each
person over time. Symptoms may be the same as those of other conditions, such
as
influenza or other viral respiratory infections or
vocal cord dysfunction. Tests done to determine
whether diseases other than asthma are causing your symptoms include the
following:
- Additional lung function tests may be needed
if other lung diseases, such as
chronic obstructive pulmonary disease (COPD), are
suspected.
- An
electrocardiogram (EKG, ECG) measures the electrical
signals that control the rhythm of your heartbeat. This test might be done to
rule out serious conditions with similar symptoms, such as
chronic heart failure.
- A
bronchoscopy involves using a flexible scope called a
bronchoscope to examine the airways. Occasionally airway problems such as
tumors or foreign bodies will create symptoms that mimic those of asthma. The
test might be done if you have unequal wheezing in the lungs or a poor response
to asthma therapy.
Biopsies of the airways can be done to look for
changes characteristic of asthma.
- A
chest X-ray may be used to see whether other lung
diseases, such as fibrous tissue caused by chronic inflammation (pulmonary
fibrosis), are causing symptoms.
- Blood tests may be done. For
example, a
complete blood count (CBC) may be done to look for
signs of an infection or other condition.
- A
sweat test, which measures the amount of salt in
sweat, may be used to see whether
cystic fibrosis is the cause of your symptoms.
Tests to identify triggers
If you have persistent
asthma and take medicine every day, your doctor may ask about your exposure to
substances (allergens) that cause an allergic reaction. For more
information about the following tests, see the topic
Allergic Rhinitis.
Allergy tests include:
- Skin tests. The skin on the back or arms is
pricked with one or more small doses of allergens that might cause an allergy.
The amount of swelling and redness at the sites of the skin pricks is measured
to see which allergens cause a reaction. Skin tests are quick, simple, and
relatively safe. Skin tests are necessary if you are interested in allergy
shots (immunotherapy).
- Enzyme-linked immunosorbent assay (ELISA).
A blood sample is taken from a vein and tested for immunoglobulin E (IgE)
antibodies, which are produced in response to particular allergens.
Other tests may be done to see whether other
conditions such as
sinusitis,
nasal polyps, or
gastroesophageal reflux disease (GERD) are
present.
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