Diagnosing Asthma - dummies

By William E. Berger, Jackie Joyner-Kersee

Effectively managing your asthma begins with your doctor correctly diagnosing your condition. In order to determine whether asthma causes your respiratory symptoms, your doctor should take your medical history, perform a physical exam, test your lung functions, and perform other tests.

The diagnostic processes that your doctor uses are crucial because asthma is not a neat little package of symptoms that you or your doctor can easily identify and eliminate. Asthma symptoms vary widely from patient to patient. In fact, your own symptoms may change over time.

The key points that your doctor should establish in diagnosing your asthma include the following:

  • You experience episodes of airway obstruction.
  • Your airway obstruction is at least partially reversible (and can be improved through treatment).
  • Your symptoms result from asthma, not from other conditions.

Taking your medical history

A careful, thorough medical history is vital in diagnosing the correct cause of your respiratory symptoms. For this reason, your doctor may ask a great number of questions about many aspects of your condition and your life. Keeping track of symptoms in a diary may help provide your doctor with details that can assist her with a proper diagnosis. Try to provide your doctor with as much information as possible about the following subjects:

  • The type of symptoms you experience, which may include coughing, wheezing, shortness of breath, chest tightness, and productive coughs (coughs that bring up mucus).
  • The pattern of your symptoms:

• Perennial (year-round), seasonal, or perennial with seasonal worsening

• Constant, episodic, or constant with episodic worsening

  • The onset of your symptoms: At what rate do your symptoms develop — rapidly or slowly? Does that rate vary?
  • The duration and frequency of your symptoms and if the type and intensity of symptoms vary at different times of day and night. Especially note if your episodes are more severe when you wake up in the morning.
  • The impact that exercise or other physical exertion has on your symptoms.
  • Your exposure to potential asthma triggers. Your doctor needs to know about endocrine factors, such as adrenal or thyroid disease, in addition to allergens, irritants, and precipitating factors. Special considerations for women are pregnancy or changes in the character or duration of their menstrual cycles.
  • The development of your disease, including any prior treatment and medication you’ve received or taken and their effectiveness. Your doctor particularly wants to know whether you presently take or have previously taken oral corticosteroids and, if so, the dosage and frequency of use.
  • Your family history, especially whether parents, siblings, or close relatives suffer from asthma, allergic or nonallergic rhinitis, other types of allergies, sinusitis, or nasal polyps.
  • Your social history, including

• The characteristics of your home, such as its age and location, type of cooling and heating system, condition of the basement, whether you have a wood-burning stove, humidifier, carpet over concrete, mold and mildew, and the types of bedding, carpeting, and furniture coverings that you use.

• Whether anyone smokes in your home or the other locations where you spend time, such as work or school.

• Any history of substance abuse.

  • The impact of the disease on you and your family, such as

• Any life-threatening symptoms, emergency or urgent care treatments, or hospitalizations.

• The number of days you (or your child with asthma) tend to miss from school or work, the economic impact of the disease, and its effect on your recreational activities.

• If your child has asthma, your doctor may ask you about the effects of the illness on your youngster’s growth, development, behavior, and extent of participation in sports.

  • Your knowledge, perception, and beliefs about asthma and long-term management of the disease, as well as your ability to cope with the illness.
  • The level of support you receive from your family and their abilities to recognize and assist you in case your symptoms suddenly worsen.

Examining your condition

A physical exam for suspected asthma usually focuses not just on your breathing passageways, but also on other characteristics and symptoms of atopic disease (relating to allergies or asthma). The significant physical signs of asthma or allergy that your doctor looks for primarily include

  • Chest deformity, such as an expanded or over-inflated chest, as well as hunched shoulders
  • Coughing, wheezing, shortness of breath, and other respiratory symptoms
  • Increased nasal discharge, swelling, and the presence of nasal polyps
  • Signs of sinus disease, such as thick or discolored nasal discharge
  • Any allergic skin conditions, such as atopic dermatitis (eczema)

Testing your lungs

Objective pulmonary-function tests are the most reliable means of assessing the extent to which your lung function is limited or affected. The following are some of the important tests that doctors use to diagnose asthma.


In order to determine whether you have airway obstruction and whether your condition is reversible (can improve with appropriate treatment), doctors often use a spirometer to measure the volume of air you exhale from your large and small airways before and 15 minutes after inhaling a short-acting inhaled beta2-adrenergic bronchodilator.

Your doctor compares the values obtained from spirometry (lung function tests) to the predicted normal reference values, based on your age, height, sex, and race, as established by the American Thoracic Society.

Doctors consider spirometry a valuable diagnostic tool for diagnosing childhood cases of asthma in children over 4 years old. However, for children under that age, the test can be difficult, if not impossible, to perform. In those cases, your child’s physician may decide that trying a peak flow meter or other less complicated assessment process is more appropriate.

Peak flow meters

Just as diabetics check their blood sugar levels with a monitoring device and people with hypertension take their own blood pressure, you can also keep an eye on your lung functions at home with a peak flow meter. Peak flow meters, which are available in a variety of shapes and sizes from different manufacturers, are convenient, portable, and easy-to-use devices for monitoring peak expiratory flow rate (PEFR), the maximum rate of air (in liters per minute) that you can force out of your large airways, as a measurement of lung function.

This measurement isn’t as accurate as spirometry, but you can perform it easily at home. Measurements of PEFR are also a vital part of long-term management of your asthma.


If spirometry indicates normal or near-normal lung functions but asthma continues to seem the most likely cause of your symptoms, your doctor may decide that a form of challenge test is necessary for a more conclusive diagnosis.

Challenge tests usually involve your doctor’s administering small doses of inhaled methacholine or histamine to you or making you exercise under her observation. The goal of such tests is to see if these challenges cause obstructive changes in your airways, thus provoking mild asthma symptoms. Your doctor usually measures your lung functions before and after each test.