Asthma: Steps in diagnosis

Asthma symptoms raise a red flag, but firm diagnosis of asthma is more complicated.

If you have bouts of wheezing, coughing and shortness of breath, your doctor may suspect asthma. But symptoms alone aren't enough for him or her to arrive at a diagnosis of asthma. Your doctor will also need to understand how, when and where your symptoms occur. After gathering that information, your doctor will probably recommend a lung function test, followed by a trial of medication that helps people with asthma breathe more easily. If the medication works, you probably do have asthma.

Diagnosis of asthma: Medical history holds clues

During an assessment for asthma, your doctor may ask a series of questions about your symptoms. It's best if you can provide detailed answers. Here are some questions that explore symptoms of asthma and help with the diagnosis of asthma.

During the past 12 months, have you:

• Had a sudden, severe episode or recurrent episodes of wheezing, coughing or shortness of breath?
• Had colds that "go to the chest" or take more than 10 days to get over?
• Had wheezing, coughing or shortness of breath only when you're in certain places, such as your home or workplace, or outdoors?
• Had wheezing, coughing or shortness of breath when exposed to certain substances such as pollen, tobacco smoke, cat dander or perfume?
• Used any medications that help you breathe better? If so, how often did you use them and how well did they work?

In the past four weeks, have you had wheezing, coughing or shortness of breath:

• At night that has awakened you?
• In the early morning?
• After running, moderate exercise or other physical activity?

A "yes" answer to any of these questions may suggest that you have asthma.

Because the tendency to develop asthma may run in families, be prepared to talk about your family's health history. Your childhood illnesses and exposure to certain substances are also of interest. These questions may include:

• Have your parents, brothers, sisters or children ever been diagnosed with asthma, allergies, sinusitis or nasal growths (polyps)?
• Have you ever been diagnosed with an allergic condition such as hay fever or eczema?
• As a young child, did you ever develop pneumonia?
• As a young child, were you exposed to second-hand smoke from your parents or other family members?

Physical exam: Detecting signs of asthma

A physical examination of your upper respiratory tract, chest and skin generally follows the history. Using a nasal speculum, your doctor may look inside your nose for signs of allergic disease such as increased nasal secretions, swelling or polyps. These signs may suggest that allergies are responsible for triggering your suspected asthma.

Your doctor also may use a stethoscope to listen to the sounds your lungs make as you breathe. Wheezing sounds indicate one of the main signs of asthma: obstructed airways.

Finally, your doctor may examine your skin for signs of allergic conditions such as eczema or hives, which are often associated with asthma.

Lung function tests: Measurements of breathing to assess possible asthma

Although your symptoms, medical history and physical examination may suggest that you have asthma, one final step, a lung (pulmonary) function test, is required to confirm an asthma diagnosis. A pulmonary function test may include one or more of the following tests.

Spirometer

Spirometry
This noninvasive test, which takes 10 to 15 minutes and measures how well you breathe, is the preferred test for diagnosing asthma. During spirometry, you take deep breaths and forcefully exhale into a hose connected to a machine called a spirometer.

Spirometry measures three values that are important in diagnosing asthma:

• Vital capacity, which is the maximum amount of air that you can inhale and exhale
• Peak expiratory flow rate, also known as the peak flow rate, which is the maximum flow rate you can generate during a forced exhalation
• Forced expiratory volume, which is the maximum amount of air you can exhale in one second

If certain key measurements are below normal for a person your age, it may be a sign that your airways are obstructed. Your doctor may ask you to inhale a bronchodilator drug used in asthma treatment to open obstructed air passages. Then you retake the spirometry test. If your measurements improve significantly, it's likely that you have asthma.

Spirometry isn't foolproof. Your doctor may still suspect that you have asthma even if your initial spirometry measurements are normal. If so, he or she may recommend the next test — a challenge test.

Challenge test
During this test, you deliberately trigger airway obstruction and asthma symptoms by inhaling an airway-constricting chemical or taking several breaths of cold air. If you appear to have exercise-induced asthma, you may bring on symptoms by doing vigorous physical activity.

After inhaling the symptom-producing substance or engaging in physical activity, you retake the spirometry test. If your spirometry measurements are still normal, it's likely that you don't have asthma. But if your measurements have fallen significantly, it may be an indication that you have asthma.

Peak expiratory flow
This test, an alternative to spirometry, also measures how well you breathe. What you do is exhale forcefully into a peak flow meter, a small, hand-held device that measures the rate at which you can force air out of your lungs.

Although peak expiratory flow is less accurate than spirometry in measuring airway obstruction, it can still play a role in asthma diagnosis. If your spirometry and challenge tests are normal but your doctor still suspects asthma, he or she may send you home with a peak flow meter and a trial prescription for asthma medications.

Over a six- to eight-week period, you record your peak flow readings before and after taking your medications. If your readings improve significantly, it may be the evidence your doctor needs to make an asthma diagnosis.

Additional tests: Ruling out conditions other than asthma

Your doctor may suspect that you have a condition other than or in addition to asthma. Possibilities include chronic obstructive pulmonary disease (COPD), pneumonia, bronchitis, pulmonary embolism, panic disorder and heart failure, all of which may mimic asthma. Conditions that often accompany asthma include gastroesophageal reflux disease, hay fever and sinusitis.

If your doctor suspects that you have another condition, he or she may conduct other tests or assessments, such as:

• Complete blood count
• Chest and sinus X-rays
• Computerized tomography (CT) scans
• Gastroesophageal reflux assessment
• Sputum induction and examination

Your doctor may also perform allergy tests. Although allergy tests aren't used to diagnose asthma, they can help identify substances that may be causing or worsening your asthma.

Diagnosing asthma in children

When assessing children under age 5, doctors seldom conduct lung function tests because young children usually have trouble following the instructions. Instead, when a child's signs and symptoms, medical history and physical examination suggest asthma, the doctor may prescribe a bronchodilator — a drug that opens the airways. If your child's signs and symptoms improve after using the bronchodilator, an asthma diagnosis is likely.

A new diagnostic approach: Exhaled nitric oxide

Because diagnostic tests such as spirometry aren't always accurate, doctors are looking for better ways to diagnose asthma. One newer approach is to measure a chemical marker of asthma — nitric oxide — in exhaled air. In general, higher levels of nitric oxide correspond with higher degrees of asthma severity.

You have asthma: Now what?

Your asthma treatment program will depend on the severity of your symptoms, indicated mainly by how often you have bouts of wheezing, coughing and breathlessness. Determining asthma severity and identifying the best treatment can take some trial and error, so you may find it more challenging than diagnostic testing. To get control of asthma, you'll need to carefully monitor your symptoms and peak flow meter readings and take your medications exactly as directed. Just as important, you'll need to be flexible about changing medication routines if your doctor recommends it. Your improved health will be well worth the time and effort you invest in getting a firm diagnosis of asthma and developing an asthma treatment plan that keeps your symptoms at bay.

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