Testing and Diagnosis

PART 1 How Does Your Doctor Determine If You Have Asthma?

Your doctor will first take your medical history and ask you about your symptoms. He or she will probably listen to your lungs using a stethoscope, although there may be no abnormal chest sounds between asthma attacks. Your doctor may ask about any patterns relating to your symptoms: are they worse during allergy seasons, at work or at home, during exercise? Do you have a family history of asthma? READ MORE

If it seems likely that you have asthma, your doctor will usually perform pulmonary function tests. These tests can diagnose asthma, if it is present, and also determine its severity. LESS

PART 2 Pulmonary Function Tests

Pulmonary (lung) function tests are used to evaluate how well your lungs are functioning. They can be used to diagnose asthma and to see if it is getting better or worse, because that can’t always be determined from your symptoms alone. READ MORE

Spirometry testing is performed using a spirometer, an instrument that measures the amount of air inhaled into and exhaled from your lungs. Spirometry testing may be done before and after you inhale a bronchodilator (a drug used to open airways) to see if the medication helps you breathe. If it does, then you may have asthma. Spirometry may also be done during exercise to see how your airways react to exertion.

Spirometers measure:
- Vital capacity (VC), the amount of air you exhale when breathing normally
- Forced vital capacity (FVC), the amount of air you can forcefully exhale after a maximal inhalation
- Forced expiratory volume (FEV1), the maximum amount of air you can forcefully exhale in 1 second

Challenge tests are used to help confirm a diagnosis of asthma. In a challenge test, you inhale a small amount of a substance that can trigger asthma, such as metacholine or histamine. Then your lung function is tested. If you don’t have asthma, there should be no change in your breathing. If you do have asthma, more airway resistance will be present. This test isn’t always accurate, however, especially if your only symptom is coughing.
- Cold air can also be inhaled to induce airway resistance.

Peak flow meter tests use a simple, handheld device to measure how well your lungs push air out. You may be asked to use the peak flow meter every day and record the results for a period of several weeks. Keeping track of how well your lungs are functioning can help you and your doctor to know what makes your asthma better or worse and whether your treatment is working. A peak flow meter can let you see if an attack is coming, even before any symptoms appear. It can also let you know if you need emergency care.

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PART 3 Other Tests

Blood tests may be given to measure eosinophil count and IgE (a type of immunoglobulin, an immune system protein)

Allergy testing can find out if you’re allergic to certain substances, termed allergens. Allergens can trigger asthma. Allergy testing can be done by pricking your skin or injecting you with a very small amount of the substance, or by doing a blood test. Being allergic to something doesn’t necessarily mean that substance is triggering asthma attacks, however, so the next step is to determine if your allergy attacks occur after exposure to the allergen.

PART 4 Classification of Asthma

Asthma is classified into four groups, according to severity: intermittent, mild persistent, moderate persistent, and severe persistent. Doctors make this classification by looking at six different components of severity:

Symptom frequency, ranging from fewer than 2 days per week to throughout the day

Nighttime awakenings, ranging from none to nightly

Use of quick-relief medication for symptom control, ranging from 2 or fewer days per week to several times per day

How much normal activity is limited by asthma symptoms, ranging from not at all to extremely limited

Lung function as measured by FEV1 and FEV1/FVC, measured with pulmonary function testing at the doctor's office

Number of exacerbations (sudden worsening) requiring oral corticosteroids, ranging from none to two or more in the last 6 months

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PART 5 Diseases That Can Be Confused with Asthma

Panic disorder may be confused with asthma because symptoms of a panic attack can mimic those of an asthma attack. Panic attacks may also coincide with asthma attacks.

Chronic bronchitis and emphysema affect the lungs in ways similar to asthma. Sometimes all three diseases may be present in the same person.

Heart failure, cancer, allergic reactions, gastroesophageal reflux disease (GERD), pneumonia, and pulmonary embolism all need to be ruled out for a diagnosis of asthma.