Diagnosing Asthma

At NYU Langone, our pulmonary, or lung, specialists have extensive experience in diagnosing asthma, a common, chronic disease characterized by inflammation and swelling of the bronchial tubes, the airways in your lungs. In people who have asthma, certain triggers—such as allergens, exercise, or cold weather—cause what’s called a hyper-responsive reaction in the airways. 

When triggered, the airways respond in ways that make it more difficult for air to move in and out of the lungs. The bands of muscle around the bronchial tubes tighten and go into spasm, and the lining of the airways becomes inflamed and swollen, which narrows them. Also, mucus production in the airways increases. These reactions result in symptoms such as coughing, wheezing, shortness of breath, and tightness in the chest. 

Most often, the difficulty with breathing comes upon exhalation rather than inhalation, but in severe episodes—commonly referred to as asthma attacks—there can be trouble with both. 

Scientific evidence suggests that asthma develops when repeated exposure to triggers results in the accumulation of cells called eosinophils. Eosinophils are a type of white blood cell that helps to protect the body from foreign substances in the airways and lungs. 

Eosinophils, acting in their protective capacity, release other substances, which cause inflammation, making the airways hypersensitive to triggers. People who are predisposed to asthma may become significantly more symptomatic with increased exposure to allergens. 

Asthma Triggers

An asthma trigger is anything that worsens symptoms or can bring on an attack. Common triggers include allergens in the environment, such as pollen, dust, mold, and pet dander (shed skin cells), as well as foods you may be allergic to, such as peanuts or shellfish. Other environmental factors, such as cold weather, humidity, smoking, or exposure to secondhand smoke, dust, fumes, or pollution, may also trigger asthma symptoms. In some people, exercise alone can trigger symptoms.

Some health conditions can exacerbate asthma symptoms or be an underlying cause. Gastroesophageal reflux disease, or GERD, for instance, may lead to asthma when stomach acid travels back up into the esophagus and is inhaled into the lungs, irritating the airways. Sinus conditions, such as viral and bacterial infections or chronic sinusitis, can also lead to asthma. 

Stress and anxiety can trigger a reaction that leads to airway constriction and makes your asthma symptoms worse.

Asthma can begin at any age. Some people with an elevated risk of developing asthma include people with a family history of the disease; those with specific allergies to foods or substances in the environment; and those who live in urban areas, which tend to have a lot of pollution. 

Diagnostic Tests

Sometimes an asthma attack can be so severe that it requires immediate emergency care. With appropriate diagnosis and treatment, however, most people with asthma can control their symptoms and avoid attacks. 

To diagnose asthma, your NYU Langone pulmonologist asks you about your symptoms and when you typically experience them. Additional tests can help your doctor determine how well your lungs are working. Your doctor may also recommend allergy testing to help identify specific allergens that may trigger symptoms.

Spirometry

Spirometry is the test most commonly used to assess lung function. People who have asthma can’t exhale as much air as others because of narrowed airways. Spirometry measures how much and how quickly you can move air out of your lungs. 

During the test, your doctor asks you to take a deep breath in and forcefully breathe out into a mouthpiece attached to a recording device called a spirometer. The amount of air you can breathe out in the first second of your exhalation, also known as your FEV1, is measured by the spirometer and printed out on a chart called a spirogram. 

Your doctor may also ask you to repeat the test after using a bronchodilator, an inhaled medication that opens the airways, to see whether it improves your breathing. This helps your doctor to determine whether medication may be an appropriate treatment for you. 

Exhaled Nitric Oxide 

Elevated levels of a molecule known as nitric oxide in your exhaled breath could signal that your airways are inflamed and could point to asthma. To perform this test, you breathe into the mouthpiece of a machine designed to measure the level of nitric oxide in exhaled breath.

Bronchoprovocation

If the results of other lung function tests are inconclusive, your doctor may perform a test called bronchoprovocation to confirm a diagnosis of asthma. During this test, your doctor exposes you to common asthma triggers while using spirometry to measure how the triggers affect your breathing. 

Your doctor may ask you to ride a bike, breathe in cold air, or inhale a medication called methacholine, which causes narrowing of the airways in people with asthma. Your FEV1 is measured before the test, to establish a baseline, and every few minutes during the test to see whether the triggers produce a reduction in airflow. This test is performed in NYU Langone’s Rusk Pulmonary Function Lab.

Allergy Testing

Your doctor may recommend allergy testing for additional insight into triggers that cause your asthma symptoms. 

An allergist draws a small sample of blood and tests it for specific antibodies that indicate an allergic reaction. Allergy blood tests can be helpful in determining your sensitivity to certain allergens, especially those commonly found in the environment such as mold, grass, and pollen. When you know what you are sensitive to, you and your doctor can work on ways to avoid the triggers or treat reactions if they occur. 

Another common allergy test is a skin prick test, in which an allergist pricks the surface of your skin—usually on your forearm—with a small needle and places tiny amounts of common allergens into the skin, such as pollen and mold. If you are allergic to a substance, your immune system produces antibodies to it, causing your skin in that spot to become swollen or itchy, usually in about 15 or 20 minutes; the reaction lasts only for a short time. 

Your doctor may also perform what is known as a patch test, where he or she applies a common allergen to a patch and puts it on your skin—usually on your back—for 48 hours. If your skin reacts to the patch, you likely have an allergy to that substance.