Question

Asthma Diagnosis

How is asthma diagnosed?

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  • It can be hard to tell if someone has asthma, especially in children under age five. Having a doctor check how well your lungs work and check for allergies can help you find out if you have asthma.

    During a checkup, the doctor will ask if you cough a lot, especially at night, and whether your breathing problems are worse after physical activity or at certain times of year. The doctor will also ask about chest tightness, wheezing, and colds lasting more than 10 days. They will ask whether anyone in your family has or has had asthma, allergies, or other breathing problems, and they will ask questions about your home. The doctor will also ask if you have missed school or work and about any trouble you may have doing certain things.

    The doctor will also do a breathing test, called spirometry, to find out how well your lungs are working. The doctor will use a computer with a mouthpiece to test how much air you can breathe out after taking a very deep breath. The spirometer can measure airflow before and after you use asthma medicine.

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  • To establish a diagnosis of asthma, healthcare providers should determine the following:
    • Episodic symptoms of airflow obstruction or airway hyper-responsiveness are present;
    • Airflow obstruction is at least partially reversible; and
    • Alternative diagnoses are excluded (e.g., vocal cord dysfunction, cough-variant forms of asthma, physiologic dyspnea and protracted or persistent bacterial bronchitis).
    In young children and infants, particularly “happy wheezers” or children with primarily “noisy breathing,” also consider etiologies such as laryngomalacia, tracheobronchomalacia, structural airway disease and congenital abnormalities. Common comorbidities include obstructive sleep apnea, allergic bronchopulmonary aspergillosis and gastroesophageal reflux, which should be aggressively treated and evaluated.

    In addition to a detailed history and physical exam, accurate and reliable pulmonary function testing (spirometry) is crucial to establishing a diagnosis of asthma and excluding alternative diagnoses. Spirometry before and after inhalation of a short-acting bronchodilator should be performed in patients 5 years old for whom an asthma diagnosis is being considered. Spirometric indices most often used to evaluate obstructive lung disease and asthma are the forced expiratory volume in the first second (FEV1) of forced exhalation expressed as either a percent of the predicted value or as a percent of the forced vital capacity (FVC), an FEV1-to-FVC ratio.

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  • Here’s what your doctor may do to gather information before an asthma diagnosis:

    • During the medical history, your doctor will ask questions about your symptoms and what seems to trigger them. Your doctor will pay particular attention to repeated symptoms. Try to provide as many details as possible, even if they seem unrelated.

    • During your physical examination, your doctor may listen to your breathing and heartbeat, and check your body for signs of allergies. (Allergies are common asthma triggers.)

    • A lung function test (also called a pulmonary function test, or PFT), shows how well your lungs are working. For example, spirometry measures how much air you can breathe out and how fast. In addition to other readings, spirometry can give your forced expiratory volume, or FEV1. FEV1 is the volume of air you can blow out in one second -- and it is a useful measure both for diagnosing asthma and for checking asthma control later on. Note that for young children -- who often aren’t able to perform lung tests correctly -- doctors often rely on a medical history and physical exam to diagnose asthma.

    • With various other tests, your doctor may gather more information about your lungs, your breathing, and your asthma triggers. For example, chest x-rays can help rule out other lung problems that could be causing your symptoms. Blood tests and skin prick tests can check for allergies that might cause your asthma symptoms.
  • Your health care provider will ask about your medical history including whether any of your family members have asthma and if you smoke, have allergies, or are exposed to pollutants. During a physical exam, your health care provider will ask you to breathe normally into a mouthpiece attached to a machine called a spirometer. A spirometer measures the amount and speed at which you breathe air in and out of your lungs. You may also be asked to use a peak flow meter during the office visit as well as later to monitor your symptoms at home. This device measures how well you can breathe out air from your lungs. Your health care provider also may use blood tests, allergy tests, and sinus or chest X-rays to aid in the diagnosis.

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