An asthma diagnosis is based on a person's medical history, physical exam, and several diagnostic tests. Once asthma is diagnosed, the doctor then identifies the person's asthma level, which in turn determines the asthma treatment.
Medical historyThe first step in diagnosing asthma is to compile a medical history. Questionnaires and interviews are used to gather information concerning their:
- Personal and family history of asthma and allergies.
- Prior history of chest colds lasting longer than 10 days duration.
- Attacks of wheezing, coughing, difficulty breathing, or chest tightness.
- Possible triggers of these attacks.
- Current medications.
Physical examDuring the physical exam, the doctor looks for typical asthma and allergy symptoms, such as:
- Airway obstruction
- Bluish lip and finger skin color
- Breathing sounds, such as wheezing
- Difficulty talking
Lung function testsLung function tests determine the health of a person's lungs by examining how well the lungs move air into and out of the body. The results of the medical history and physical exam determine which lung function tests are given. Lung function tests include:
- Spiromety test
During a spirometry test, people breathe into a spirometer (a device that measures the volume of air entering and leaving the lungs). The test may be repeated after a bronchodilator (medicine that helps open airways in the lungs) is given to see if the medicine improves the test results. Some people with asthma may have a normal spirometry test.
- Peak flow meter testing
When asthma is suspected and the spirometry test results are normal, a peak flow meter (a small, handheld device that measures lung function) may be used to determine a person's lung function over time. A person uses a peak flow meter and records the results every day for one or two weeks. The results are then reviewed during a follow-up doctor visit.
- Exercise challenge test
The exercise challenge test is used for people whose asthma is believed to be triggered by exercise. A spirometer tests their lung function before and after exercising.
- Bronchial challenge test
The bronchial challenge test is used to identify a person's allergen and irritant triggers. In this test, a person uses a spirometer before and after being exposed to suspected allergens and irritants.
- NIOX Nitric Oxide Test System
In 2003 the Food and Drug Administration (FDA) approved the NIOX Nitric Oxide Test System to monitor a person's asthma. The device measures the concentration of nitric oxide in exhaled breath. Doctors use the noninvasive test to determine whether or not a person's asthma treatment is working.
Chest and sinus X-raysChest and sinus X-rays produce pictures of a person's lungs and sinuses. Because asthma symptoms resemble other respiratory conditions, when a person experiencing respiratory problems visits a doctor, it's important to rule out other respiratory conditions. X-rays help identify if inflammation is present as well as rule out other respiratory infections.
Pulse oximeterA pulse oximeter placed on the fingertip measures the amount of oxygen in the bloodstream.
Arterial blood gasAn arterial blood gas test measures the amount of oxygen and carbon dioxide in the blood. The test measures how well the lungs are delivering oxygen to the blood and removing carbon dioxide from it.
Complete blood countA complete blood count tests a person's blood for signs of an infection that might be causing a person's asthma symptoms.
GERD testingGastroesophageal reflux disease (GERD) is a condition that causes food or liquid to flow backwards from the stomach to the mouth. The testing indicates if a person's asthma is triggered by GERD.
Allergy testingAllergy testing isn't used to diagnose asthma. Instead, it is sometimes used to identify a person's sensitivity to various allergens. Allergy testing also helps determine if the allergens identified cause a person's asthma or make it worse.
- Antibody testing
Antibody testing measures blood antibodies (substances released by the immune system that neutralize foreign substances).
- Skin testing
Skin testing exposes a person's skin to allergy-causing substances (allergens). The skin is then observed for signs of an allergic reaction.
Diagnosing Childhood AsthmaParents provide medical history information about their child's asthma symptoms and family background. The child is then given a physical exam and a chest X-ray. Only children older than 5 are given lung function tests, because the tests are not as reliable for younger children. Depending on the symptoms, some children may be tested for allergies or GERD.