Exams and Tests

Diagnosis of asthma is based on medical history, a physical exam, and simple lung function tests such as spirometry.

Diagnosing asthma in babies and toddlers is often very difficult. Symptoms may be the same as those of other diseases, such as infection with respiratory syncytial virus (RSV) or inflammation of the lungs (pneumonia), sinuses (sinusitis), and small airways (bronchiolitis). If you have a very young child, spirometry is not practical. So the diagnosis is made based on your report of symptoms.

Lung function tests

In an older child, lung function tests can diagnose asthma, determine its severity, and check for complications.

• Spirometry is the most common test to diagnose asthma in older children. It measures how quickly a child can move air in and out of the lungs and how much air is moved.
• Testing of daytime changes in peak expiratory flow (PEF) is done over 1 to 2 weeks. This test is needed when your child has symptoms off and on but has normal spirometry test results.
• An exercise or inhalation challenge may be used if the spirometry test results have been normal or near normal but asthma is still suspected. These tests measure how quickly your child can breathe in and out after exercise or after using a medicine. An inhalation challenge also may be done using a specific irritant or allergen.
• A bronchoscopy test involves using a flexible scope called a bronchoscope to examine the airways. Sometimes airway problems such as tumors or foreign bodies will create symptoms that mimic those of asthma.

A newer test to monitor asthma is the NIOX nitric oxide test system. This test measures nitric oxide in exhaled air. A decrease in nitric oxide suggests that treatment may be reducing inflammation caused by asthma. But some experts believe that this test is not useful for monitoring asthma.¹¹

Tests for other diseases

Asthma sometimes is hard to diagnose because symptoms vary widely from child to child and within each child over time. Symptoms may be the same as those of other conditions, such as influenza or other viral respiratory infections. Tests that may be done to determine whether diseases other than asthma are causing your child's symptoms include:

• A chest X-ray. A chest X-ray may be used to see whether something else, such as a foreign object, is causing symptoms.
• A sweat test, which measures the amount of salt in sweat. This test may be used to see whether cystic fibrosis is causing symptoms.

Other tests may be done to see whether your child has health problems such as sinusitis, nasal polyps, or gastroesophageal reflux disease.

Regular checkups

You need to monitor your child's condition and have regular checkups to keep asthma under control and to review and possibly update your child's asthma action plan. The frequency of checkups depends on how your child's asthma is classified. Checkups are recommended:

• About every 6 to 12 months for children with intermittent or mild persistent asthma that has been under control for at least 3 months.
• Every 3 to 4 months for children with moderate persistent asthma.
• Every 1 to 2 months for children with uncontrolled or severe persistent asthma.

During checkups, your doctor will ask you and your child whether symptoms and peak expiratory flow have held steady, improved, or become worse. He or she will also ask about asthma attacks during exercise, at night, or after laughing or crying hard. You and your child track this information in an asthma diary.

Your child may be asked to bring the peak expiratory flow meter and inhaler to an appointment so your doctor can see how he or she uses them. Based on the results, your child's asthma category may change. And your doctor may change the medicines your child uses or how much medicine he or she uses.

Tests to identify triggers

If your child has persistent asthma and takes medicine every day, your doctor may ask about his or her exposure to substances (allergens) that cause an allergic reaction. For more information about tests for allergies, see the topic Allergic Rhinitis.