To diagnose asthma, the doctor will see if three criteria are met:
- You have recurring episodes where your airflow becomes blocked, resulting
in at least one of the asthma signs
- The blocked airflow can be at least partially reversed through medication
(see spirometry, below)
- Other potential causes of your symptoms are ruled out
The doctor will want to evaluate your medical history to identify what symptoms
you have had, when your symptoms occur, and how long they last. The doctor
will ask about possible triggers, such as allergens, exercise, or occupational
exposure to chemicals. The doctor will also want to know if you have a family
history of asthma, allergy, sinusitis, or nasal polyps.
The doctor will conduct a physical exam that focuses on the upper respiratory
tract, chest, and skin. The doctor will listen for wheezing and may look for
nasal secretions, eczema, and similar allergy-related symptoms.
Lung function tests
Spirometry is the most reliable test for diagnosing asthma. A spirometer is
an instrument that measures the maximum volume you can exhale after breathing
in as much as you can. The total volume you exhale is called "forced vital
capacity," or FVC. The spirometer also measures the volume of air you exhale
in the first second. (This is referred to as "forced expiratory volume in one
second," or FEV1.) In general, the more air you breathe out during the first
second of a full exhalation, the better.
The doctor will take the reading several times. Your FVC and FEV1 results
will be compared to what is normally seen in people without any blockage in
their airways. Your doctor will have a good idea just from this data how much "obstruction" is
in your airways.
Then, you will be given a bronchodilator, a drug that relaxes the muscles
of your airways. After the drug has had time to take effect, you blow into
the spirometer again. If you can breathe out significantly more air during
the first second than you could before, it indicates that your breathing obstruction
is "reversible." This is a strong indication of asthma.
Many doctors use a "peak flow meter" to diagnose asthma. This simple, portable
device is available in most doctor's offices and may allow a doctor to quickly
and easily determine whether asthma is your problem.
Because both spirometry and peak flow measurements require coordinated cooperation
from the person being tested, they may not be practical in children younger
than 6. (About 80% of all asthma begins before age 6). In younger children,
lung function can be measured by a technique called forced oscillation, which
simply involves breathing vibrating air. Often the diagnosis is based on the
medical history and physical exam, perhaps with some other supporting tests.
No one single test, or set of tests, is appropriate for every patient. Your
doctor may use other tests, such as chest x-rays, to help rule out the possibility
of other causes of your symptoms. The doctor may perform additional lung function
tests to rule out bronchitis or emphysema (especially
if you are a smoker or an older patient).
A test called "bronchoprovocation" may be performed if the doctor strongly
suspects asthma but your spirometry readings were normal. (This test must be
conducted by a trained specialist in an appropriate facility.) Other tests
include chest x-rays, allergy testing, examinations for nasal polyps or sinusitis,
and evaluation for gastroesophageal reflux.
Allergy testing can provide important supportive evidence [the Childhood Asthma
Management Program (CAMP) reports that about 88% of school-aged children with
asthma have positive allergy prick skin tests to inhaled allergens]. Not only
can allergy testing support the diagnosis, but treating the allergies can help
manage the asthma. Allergy test results can help predict the long-term course
of child asthma.
Throat Clearing - An Important Clue?
Might throat-clearing be an overlooked symptom of asthma? Researchers
surveyed the parents of over 2,500 3- to 5-year-old children attending
daycare on the island of Crete. Among the questions asked: "Does your
child have a habit of clearing his or her throat often?" More than 100
parents said yes. Many of those children already had been diagnosed with
asthma, but most had not.
When pulmonary function testing was performed on the children believed
not to have asthma, the results were enlightening: These children all had
mild asthma that had not yet been suspected! And their lung function
and throat clearing improved with asthma medicines. The study, published
in the April 10, 2003, issue of the New England Journal of Medicine,
suggests that throat clearing may be the first sign of asthma in some
children. Children with asthma fare better with early diagnosis and
early treatment. It might be wise for doctors thinking about asthma
to ask parents about throat clearing, and for parents whose children
often clear the throat to ask their doctors about asthma testing.
If it is asthma...
If you or your child has asthma or recurrent wheezing, ask your doctor what
category of asthma it is. Those with mild intermittent asthma might be managed
with occasional albuterol use. Those with mild persistent asthma (or moderate
or severe persistent asthma) fare much better if they also receive anti-inflammatory
or preventive medicines. One study, though, found that most children with persistent
asthma are assumed by doctors and parents to have intermittent asthma. Thus,
they miss out on getting the right medicines -- medicines that could actually
improve their asthma and result in less albuterol being needed. Classifying
your asthma is a conversation you want to have!
If it's not asthma...
According to the National Institutes of Health, "recurring episodes of cough
and wheezing are almost always due to asthma in both children and adults." However,
there are other possibilities. A certain amount of airway inflammation and
narrowing are NORMAL responses to airborne irritants. Recurrent wheezing could
come from ongoing exposure to chemical fumes, for example. It's only asthma
if the narrowing is out of proportion to the threat to the lungs. And in young
adults, "vocal cord dysfunction" can cause symptoms very similar to asthma,
such as shortness of breath and wheezing.
Regardless of age, if asthma is ruled out, your doctor will explain other
National Asthma Education and Prevention Program Expert Panel Report: guidelines
for the diagnosis and management of asthma update on selected topics -- 2002. J
Allergy Clin Immunol. 2002 Nov;110(5 pt 2):S141-219.
National Asthma Education and Prevention Program Expert Panel Report 2:
guidelines for the diagnosis and management of asthma. Bethesda (MD):
U.S. Department of Health and Human Services, Public Health Service, National
Institutes of Health, National Heart, Lung and Blood Institute; 1997 Jul.
NIH Publications 97-4051.
Williams SG, Schmidt DK, Redd SC, Storms W. Key clinical activities for quality
asthma care: recommendations of the National Asthma Education and Prevention
Program. MMWR Recomm Rep. 2003 Mar 28;52(RR-6):1-8.
Review Date: 5/16/2007
Reviewed By: Alan Greene, M.D., F.A.A.P., Department of Pediatrics, Packard Children's Hospital, Stanford University School of Medicine; Chief Medical Officer, A.D.A.M., Inc.
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