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Exercise-Induced Asthma: Differential Diagnoses & Workup

Author: Anthony J Saglimbeni, MD, Staff Physician, Family Practice Residency, President, South Bay Sports and Preventive Medicine Associates; Private Practice; Team Internist, San Francisco Giants; Team Internist, West Valley College; Team Physician, Bellarmine College Prep; Team Physician, Presentation High School
Contributor Information and Disclosures

Updated: Jun 15, 2009

Differential Diagnoses

Anxiety
Hyperventilation Syndrome
Vocal Cord Dysfunction

Other Problems to Be Considered

Deconditioning syndrome
Seasonal asthma 
Upper airway obstruction

Workup

Laboratory Studies

• In general, EIA is diagnosed clinically and may not need any further laboratory studies, imaging, or other tests and procedures. Laboratory evaluation is reserved for equivocal cases, for treatment failures, and to narrow the differential diagnosis when it seems reasonable. Therefore, consider testing to evaluate cardiac conditions, vocal cord and upper airway obstructive conditions, allergic conditions, and psychiatric conditions.
• A complete blood cell count and differential ("CBC with diff") can help in the assessment of the likelihood of infection by analysis of the patient's white blood cells and by evaluation of the eosinophil counts (for allergy).
• An erythrocyte sedimentation rate (ESR) result may help in the evaluation of inflammatory and infectious conditions.
• Assessing the immunoglobulin E (IgE) count helps in determining the likelihood of allergic disease.
• Skin allergen testing or a radioallergosorbent test (RAST) can be used to help identify specific allergens to promote patient avoidance or immunotherapy, if indicated. Either method has been used extensively in atopic workups. In young children, RAST testing may be preferable owing to the relative ease of administration, but this is a less specific test, and therefore, skin testing may be preferred in general.
• Thyrotropin levels can be used to help evaluate the potential of patient thyroid dysfunction in the likelihood that anxiety is mimicking the symptoms of asthma.
• If the diagnosis is uncertain, performing a nasal swab for the presence of eosinophils is helpful in identifying the role of allergic rhinitis.
• Sputum analysis and culture can be used to help identify the presence of infection and treatment options for strains of resistant organisms.

Imaging Studies

• Imaging studies are often not indicated in the evaluation of routine EIA, but they may be useful for evaluating other possibilities in the differential diagnosis.
• Chest radiograph
  • To evaluate for signs of chronic lung disease (eg, hyperexpansion, scarring, fibrosis, hilar adenopathy)
  • To evaluate for congestive heart failure and/or valvular heart disease (eg, chamber enlargement, pulmonary edema, vascular or valvular calcification)
  • To evaluate for a foreign body
• Lateral neck radiographs/soft-tissue penetration to evaluate the upper airway for a foreign body or obstruction
• Echocardiography to evaluate for cardiac valvular abnormality or global contractile function

Other Tests

• Echocardiography can also be used to evaluate dysrhythmia, cardiomegaly, or other heart disease that may manifest during exercise.

Procedures

• Various challenge tests exist that can be used to formalize the diagnosis of EIA. A formal diagnosis is often not critical, clinically, but in recent years, the US Olympic Committee has required a positive challenge test to be documented for an athlete to qualify for the use of controlled substances that aid in ameliorating the symptoms of EIA. This requirement has resulted in new studies that have been used to validate some of these assessment tools, whether they are field challenges, treadmill testing, or new techniques such as eucapnic voluntary hyperventilation (EVH).^7,10,11
• Treadmill exercise challenges with preexercise and postexercise pulmonary functions
  • This type of testing formalizes an aerobic challenge and provides an objective measure of the degree of bronchospasm that results from the exercise. The results can help the physician to clarify the diagnosis and to enforce the treatment; the results can also be used to evaluate success of the treatment.
  • Before the exercise challenge, the patient's baseline pulmonary function levels should be obtained (preferably forced expiratory volume in 1 second [FEV₁], forced vital capacity [FVC], or FEV₁/FVC, or, less ideally, peak expiratory flow rate [PEFR]). The exercise challenge involves exercising the athlete on a treadmill until his or her heart rate reaches 70-85% of the maximum predicted heart rate. This is maintained for 6-10 minutes, at which time the exercise is stopped. Pulmonary function levels are measured every 2-10 minutes for 15-30 minutes and then compared with the baseline measurements.
  • Any drop from the baseline that is greater than or equal to 10%, on any postexercise measurement, indicates EIA. Severity of disease can be classified as follows:
    • Mild – Decrease of 10-20% from baseline
    • Moderate – Decrease of 20-40% from baseline
    • Severe – Decrease of greater than 40% from baseline
• An informal exercise challenge can be substituted for the above procedure, but without monitoring the heart rate, the level of work is not reliable.
• Laryngoscopy can be performed to evaluate for foreign body or other obstruction in the upper airway.
• Postexercise laryngoscopy can be used to evaluate for vocal cord dysfunction, a condition often mistaken for EIA. Vocal cord dysfunction manifests as stridor with exercise due to paradoxical contraction of the vocal cords with inspiration; this condition can be evaluated via laryngoscopy after an exercise challenge.
• Pulmonary function testing can be used to evaluate baseline pulmonary function or allergic asthma and to categorize pulmonary function as obstructive or restrictive disease.
• Bronchoprovocation testing, as used with general asthma, methacholine, histamine, or cold air challenges, can be used to assess asthma. However, if the results are positive, they are indicative of asthma in general, not specifically EIA.
• EVH is a new technique believed to be more sensitive and more accurate for diagnosing EIA.^7,11 Furthermore, EVH can be applied in a laboratory setting and altered to mimic the environmental conditions of the sport in question.

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