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When should a child be evaluated for asthma?
A discussion with a pediatrician and/or an examination by a pediatric pulmonologist or allergist who specializes in asthma is important if a child exhibits any asthma symptoms. These symptoms include:
1) Lingering cough which usually begins as a dry, non-productive cough (audio), frequently in association with a cold or upper respiratory infection
2) Recurring coughing episodes (audio)
3) Cough with any type of physical exertion
4) Wheezing (a recurring, audible whistling wheeze) (audio)
5) Shortness of breath or difficulty breathing
6) Episodic chest tightness or pain
7) Presence of previously mentioned symptoms associated with viral infections, cigarette smoke, strong odors or fumes, allergies, changes in weather, or exercise
8) Repeated diagnoses of reactive airway disease, wheezy bronchitis, allergic bronchitis, bronchiolitis, or pneumonia
9) Cough triggered by laughing or crying
10) An itch or tickle under the chin or in the throat
11) Nocturnal (nighttime) cough or shortness of breath (audio)
There are three components to a thorough evaluation:
1) Obtaining the patient and family medical history
2) A physical examination
3) Pulmonary function (lung performance) and supplemental testing
Medical History:
During an evaluation, the physician will ask you about the presence of symptoms associated with asthma, the duration of the symptoms, and the frequency and circumstances under which they occur. Information about any emergency room visits or hospitalizations is important because it speaks to the severity and level of control of asthma. Expect to be asked such questions as: What known factors (triggers) tend to cause or aggravate symptoms? Do these symptoms interfere with physical activity, sleep or school? What impact do they have on the family's life?
Since genetics often plays an important role in the development of asthma, the physician will want to know if any immediate family member has asthma or allergies.
Also, which medications, if any, have been used so far to lessen symptoms and have they been successful.
Finally, while it may not seem especially relevant, newborn and infancy history may suggest significant causal factors. This history must be discussed to determine any possible early injury to the airways due to premature birth, viral infections or parental smoking. Supporting evidence for an alternative diagnosis to asthma, such as cystic fibrosis, congenital heart disease or vocal cord dysfunction will be sought. Questions about non-respiratory systems usually follow because such things as occult (hidden) underlying sinus infections, postnasal drip or gastroesophageal reflux may be contributing factors.
An exam concentrating on the respiratory system, with attention also paid to other systems, is key. Unless the child is in the midst of an asthma episode, the chest findings may be subtle or non-existent. Abnormal physical findings-like asthma itself-are mostly intermittent. During an episode or attack, or when there is poor asthma control, wheezing (a whistling sound on exhalation) (audio), cough, (audio) or a prolonged exhalation phase may be present. When asthma is severe, there may be retractions (a pulling in of the rib muscles or lower neck area), overexpansion of the chest cavity and rapid breathing.
It is a misnomer that every child with asthma wheezes; some may just cough or experience shortness of breath or chest tightness.
Other important findings in the physical exam may support associated atopy (allergy) such as eczema, runny nose with swollen nasal membranes (rhinitis), or dark circles under the eyes. Approximately 70% of children with asthma have associated allergies and may show these signs.
What is spirometry?
Spirometry is a two-part pulmonary function test that measures how quickly air can be forced out of the lungs. Generally, spirometry cannot be reliably performed on a child less than 5 or 6 years of age because it requires cooperation, attention and maximum effort. The first phase of the test, the baseline study, allows a physician to determine the presence and degree of airway obstruction or narrowing. If the airways are narrowed, air empties at a slower rate than normal during exhalation (breathing out) and this is reflected in the result. Since the airflow obstruction of asthma is partially caused by reversible constriction (tightening) of the muscles around the airways, a second phase is very often performed. The patient inhales a fast-acting bronchodilator and measurements are then repeated, checking for reversibility of airway narrowing --- one of the hallmarks of asthma. A significant improvement in airflow suggests asthma.
Asthma symptoms due to airway obstruction are intermittent by nature. And since pulmonary function testing offers a result for only one moment in time, spot testing may be normal or close to normal. If this is the case, and asthma is strongly suspected, there are 3 options:
1) Repeat spirometry when symptoms are occurring
2) Perform bronchoprovocative challenge spirometry
3) Institute a trial of bronchodilator medication in association with peak flow monitoring (home testing)
What are bronchoprovocative challenge tests?
Sometimes basic spirometry may not catch the air flow obstruction due to either the typically intermittent nature of the obstruction in asthma or because asthma is not the cause of the patient's symptoms. Various pulmonary challenge tests can reveal the airflow obstruction of asthma much like an exercise stress test can uncover coronary artery disease.
The methacholine challenge is probably the most commonly used pulmonary challenge study. It is a very sensitive test for asthma and bronchial hyperresponsiveness. A negative test basically rules out asthma. Inhaling tiny amounts of a chemical called methacholine leads to muscle constriction around the airways in everyone. However, it causes a much greater degree of constriction in children/teens with asthma. Like all pulmonary challenge tests, the methacholine challenge is performed very carefully and with close monitoring.
Additional challenge studies, perhaps more targeted to the child or teen with a potential diagnosis of exercise-induced asthma, will be discussed in the Exercise and Asthma section.
Will other testing be needed?
It may be necessary to do additional testing to determine if there is either an alternate diagnosis to asthma or underlying conditions that may be worsening asthma. The decision will usually depend on the physician's judgment and level of suspicion. Supplemental tests may include: blood work, a sweat test, a chest x-ray (typically normal in asthma but perhaps abnormal in other conditions), nasal swab, laryngoscopy, or a sinus CT scan.
New and exciting tests on the horizon:
1) Nitric oxide (NO) measurements: Nitric oxide is formed by the lining cells in the bronchial tubes (airways). It is a marker of inflammation. NO is found in much higher concentrations in the exhaled air of people with asthma.
2) Electronic nose: After inhaling organic compound-filtered air for several minutes, a patient exhales into a bag. The "smell print" of patients with asthma has been found to be distinctly different from those who do not have asthma.
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