Asthma is a chronic disease that affects the lungs and constricts the airways. According to the National Heart, Lung, and Blood Institute, more than 22 million people have been diagnosed with asthma. The disease can strike a person of all ages, but asthma commonly begins in childhood. Wheezing, tightness of the chest, trouble breathing and coughing are symptoms indicative of asthma. Confirming asthma likely requires a review of medical history, a physical exam and laboratory tests.

Medical History/Physical

To begin, your physician will review your medical history, including asking if asthma or allergies runs in the family. The doctor will also ask your symptoms and when your condition seems to worsen. During a physical exam, the physician will examine your breathing, looking for signs including skin conditions, blocked nasal passages and a runny nose.

Diagnostic Tests

YourLungHealth.org states that the two most common pulmonary function tests for asthma are spirometry and methacholine challenge. A spirometry determines how your lungs function by measuring how much air you inhale and exhale using a device called a spirometer. After breathing several times into the device over a 15 minute period, a respiratory therapist will compare your results with people of similar traits, such as height, age and race. These comparisons may reveal if you are asthmatic. Sometimes more testing is needed for a determination. This is when a methacholine challenge test is performed. With this test, you will inhale a drug called methacholine, which constricts the airways. The respiratory therapist will gradually increase the amount of the drug you breathe in during the test. Once the test is finished, you will once again do the spirometry test to measure any airflow changes. If lung capability falls by at least 20 percent after the methacholine challenge, you will likely be diagnosed with asthma.

Additional Tests

If spirometry and methacholine challenge still are not enough to make a diagnosis, other tests can be ordered. This includes chest x-rays, allergy tests and testing to see if you have a condition that has similar symptoms to asthma, including sleep apnea or reflux disease. A bronchoprovocation test also is effective in measuring for asthma. Using spirometry, this test examines lung capability during physical activity or after you are given escalating doses of a special aerosol.

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What Is Asthma?

Diagnosing Asthma