Diagnosing Asthma in Children

At Hassenfeld Children’s Hospital at NYU Langone, pulmonologists—doctors who treat children with lung conditions—specialize in diagnosing asthma, a condition in which the bronchial tubes, or airways, swell and tighten. This can make it difficult for a child to take a deep breath.

Asthma can appear at any age, and doctors aren’t entirely sure what causes it. Evidence suggests that asthma develops as a result of repeated exposure to the viruses and bacteria that cause respiratory infections, as well as to allergens and other irritants, such as pollen, dust, mold, cigarette smoke, air pollution, and pet dander, which is the dead skin shed by animals.

Exposure to these “triggers” stimulates the accumulation of cells in the lungs called eosinophils, a type of white blood cell that helps to protect the body from foreign substances. Eosinophils release substances that inflame the airways and make them sensitive to triggers.

When exposed to a trigger, the airways overreact. They become swollen and narrow and release mucus, leading to symptoms such as wheezing. An episode of severe symptoms that comes on suddenly is called an asthma attack.

Risk Factors

Children with asthma are not born with the condition, but having a family history of asthma raises the risk of developing it. Children who acquire nasal, skin, or food allergies at a young age have an increased risk of developing asthma. In fact, most children with asthma have some type of allergy.

Viral infections, such as respiratory syncytial virus (RSV) and the common cold, can increase a child’s risk for asthma. So can exposure to air pollutants and secondhand cigarette smoke—a leading trigger of asthma and other breathing problems in children.

Some children show asthma symptoms after vigorous exercise. Exercise-induced asthma attacks may be more common in children who are active outdoors, where they’re exposed to allergens such as pollen.


During an asthma attack, some children feel tightness in the chest as the airways become narrowed, or spastic. Others may feel out of breath or begin wheezing, an almost musical sound that occurs when a child inhales or exhales through narrowed airways. Cough-variant asthma, in which the only symptom of the condition is coughing, is more common in adults than in children.

If a child’s asthma isn’t properly controlled with medication, it can lead to an asthma attack—a flare-up of severe symptoms that may require treatment at a hospital or emergency room. Over time, uncontrolled asthma can lead to a permanent narrowing of the airways, which may increase the risk of developing chronic obstructive pulmonary disease, or COPD, during adulthood. If your child has severe uncontrolled asthma, specialists from our Pediatric Severe Asthma Program provide advanced evaluation and targeted treatments.

Diagnosing asthma requires experience with treating children who have pulmonary conditions. This is because other health conditions, such as narrowing of the airways that is present at birth, allergies, and respiratory infections, can cause asthma-like symptoms, such as wheezing, chest tightness, and coughing.

Our doctors use a variety of tests to diagnose asthma. An asthma diagnosis is confirmed if your child’s symptoms improve after using medications that open the airways.

Respiratory Exam and Medical History

A doctor asks about your child’s respiratory symptoms, such as breathlessness, and recent illnesses. You may also discuss whether your child has allergies or a family history of asthma or allergies and whether he or she has been exposed to pets, cigarette smoke, or other possible triggers.

Our doctors look for signs that your child is having difficulty breathing, such as retraction, or sinking in, of the area between the ribs. They also listen for unusual breathing sounds, such as wheezing, which can be difficult to distinguish from other breathing noises.

Lung Function Tests

Lung function tests are critical in distinguishing between asthma and other breathing problems. These tests can be performed in children as young as age 4. Doctors at Hassenfeld Children's Hospital may perform one or more of the following tests.


Spirometry determines how much and how quickly your child can blow air out of the lungs. In this test, your child inhales deeply and then exhales into a plastic tube, allowing the spirometer to measure the volume and flow of your child’s breath. This test can be performed in the doctor’s office.

Bronchodilator Challenge Test

In a bronchodilator challenge test, performed in the doctor’s office after spirometry, your child inhales a bronchodilator medication called albuterol, which opens up the airways, and exhales into the spirometer again. Your child may wear a nose clip to make sure that no air escapes through the nose during the test.

The test measures whether using the medication increases air volume and flow. Giving albuterol to healthy children is harmless and does not cause a noticeable change. However, children with asthma show a significant improvement after receiving the medication.

Impulse Oscillometry

Impulse oscillometry can help doctors diagnose asthma in younger children who have difficulty forcing air into a spirometer. In this noninvasive test, which is offered at the Pediatric Pulmonary Function Laboratory, part of Hassenfeld Children’s Hospital, your child breathes normally into a tube. The device uses sound waves that bounce off of the tube to measure the resistance to pressure in your child’s airways, which can reveal any problems with airflow.

Impulse oscillometry can also be used in combination with a bronchodilator medication to see whether it changes the resistance measured.


Plethysmography, which measures total lung capacity, may be used if a doctor suspects that your child’s symptoms are caused by a weakness in the muscles involved in breathing, rather than asthma.

In this test, performed in the Pediatric Pulmonary Function Laboratory, your child sits in an airtight booth for about three minutes and breathes or pants against a special mouthpiece. A computer calculates total lung capacity—the amount of air the lungs can hold—by measuring how the air pressure and volume in the room changes as your child breathes.

Exercise Challenge

An exercise challenge test uses spirometry to measure how well the lungs work before and after a child rides on a stationary bicycle. This test can help to distinguish exercise-induced asthma symptoms from the everyday shortness of breath seen in people who aren’t used to exercising. This test may be performed in the Pediatric Pulmonary Function Laboratory.


Bronchoscopy is a more invasive diagnostic test sometimes recommended for children who have unusual asthma symptoms, such as a chronic wet cough or persistent wheezing, that make it difficult to breathe into a spirometer. Bronchoscopy may also be used to rule out congenital lung problems—those a child is born with—that can cause asthma-like symptoms in very young children.

After giving a child a mild sedative to relax, the pulmonologist inserts a flexible tube attached to a fiber-optic camera, called a bronchoscope, through your child’s nose or mouth and into the airways. Bronchoscopy allows the doctor to see if your child’s airways appear swollen.

The doctor also uses the bronchoscope to spray saline into the airway. The saline is suctioned out and examined under a microscope to count the number of inflammatory cells contained in the sample.

Bronchoscopy is performed in the hospital. Your child can return home shortly after the procedure, which is usually completed in about 30 minutes.

Allergy Tests

Your doctor may suggest an allergy test to look for evidence of an allergy as an underlying cause of your child’s asthma symptoms. The most common type of allergy test is a skin test, which is done in the doctor’s office. In this test, the doctor gently pricks the surface of your child’s skin, usually on the back or arm, and places a small amount of several allergens, such as ragweed pollen, mold, or the proteins found in pet dander, which is the dead skin shed by animals.

Allergies increase the production of immunoglobulin E, an antibody found in blood that indicates an allergic reaction. The skin swells and feels itchy if your child is allergic to any of these substances. This reaction usually occurs within 20 minutes after the test and goes away a few minutes later.

If your child cannot have skin testing because of a skin or health condition, the doctor may use other blood tests to look for immunoglobulin E. Blood test results are usually available in two to three days.

Information from these tests helps our doctors make an asthma diagnosis and determine the severity of your child’s condition.

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