A physician is likely to use several methods to determine whether or not a person has asthma. An individual’s medical history – including prior breathing problems, allergies or skin conditions – may offer important clues. A family history of asthma, eczema or allergies also may indicate an increased risk for asthma, as the condition appears to run in families with these conditions.

The physician may assess the severity of asthma using the following criteria:

• Extent to which asthma attacks interfere with normal activities
  
  
• Severity and duration of symptoms
  
  
• Degree of airway obstruction

Mild to moderate asthma is often characterized by tightness in the chest, coughing up mucus, difficulty sleeping and wheezing. Severe attacks may be characterized by the following:

• Difficulty speaking
• Slight gray or bluish color to the lips and fingernail beds (cyanosis)
• Sucked-in appearance to the rib cage
• Breathlessness

Following the collection of a medical history, a physician will perform a physical examination to look for signs of asthma. The exam will focus on the respiratory tract, chest and skin. The physician will listen for wheezing and other sounds in the chest with a stethoscope (an instrument that uses rubber tubing that is placed in the ears and a cup-shaped device to detect sounds produced in the body). The physician will also use a nasal speculum (a handheld device with a telescope) to examine the inside of the nose for signs of allergies (e.g., swelling, polyps, increased secretions). The skin will be examined as well for signs of allergic conditions associated with asthma (e.g., eczema, hives).

Although, symptoms, a medical history and a physical exam can suggest the presence of asthma, diagnostic tests that measure an individual’s airflow are the primary means of uncovering asthma. These and other tests may include:

• Pulmonary function test. A test that measures how much air the lungs can hold and how quickly it is exhaled.
  
  
• Bronchoprovocation test. A test that involves inducing a minor asthma attack to diagnose asthma when symptoms are not present. Most bronchoprovocation tests use histamine or methacholine but may include specific agents, such as food additives or environmental allergens.
  
  
• Spirometry. A test that measures how much air a person blows out in a specific period of time, and how forcefully it is blown. It can reveal the extent of airway obstruction present, and how much of the obstruction is reversible.
  
  
• Pulse oximetry. A test in which a probe is placed on a fingertip to measure the amount of oxygen in a person’s bloodstream.
  
  
• Chest x-ray. An image of the chest produced using low doses of radiation. This test can be useful in detecting air trapped in the lungs. It may also be used to rule out other conditions and diseases known to cause symptoms similar to asthma.
  
  
• Allergy skin test. A test used to identify a specific allergen that might be triggering asthma attacks. While allergies are a separate condition from asthma, allergic reactions often trigger attacks in asthmatics. During this test, a small amount of one or more allergens is introduced to the patient’s skin (through a prick, scratch, injection or patch). The skin is then examined for a positive reaction. A hive will usually indicate that an allergy to the substance is present. The test is not 100 percent accurate, but it can be an effective tool in diagnosing allergy triggers.
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Patients can play a vital role in the ongoing diagnosis of their own asthma by using a peak flow meter. This device measures the amount of air flowing into and out of a patient’s lungs. By using it every day, patients can detect changes in their breathing capacity before the condition manifests itself in asthma symptoms. Peak flow meters can also help an individual determine the severity of an asthma attack once it has begun.

Other conditions may have similar symptoms, such as chronic obstructive pulmonary disease, emphysema, early onset of heart failure (cardiac asthma) and vocal cord dysfunction. A physician may perform other tests to rule out these conditions, including imaging tests and blood tests.