A 19-year-old boy complains of difficulty breathing during exercise. He reports being in good physical shape, but occasionally experiences coughing and have to stop and catch his breath. This seems to occur more often in cold weather. The patient has no significant medical history other than seasonal allergies, and he takes no medication. He has some patchy dry skin over the elbows with some erythema and excoriations; otherwise the physical examination is normal. He is referred for spirometry, which is normal.
Which of the following is the most appropriate next step in management?
A. Albuterol challengeMethacholine challenge. Although the diagnosis of asthma is tested more often on the Pediatrics shelf examination, it may show up on the Medicine shelf examination and therefore a brief overview may be useful. Asthma is an intermittent obstructive lung disease that is classically described as airway hyper-responsiveness with variable airflow obstruction. It is a common condition, especially in those with other features of the atopic triad (seasonal allergies, eczema, and asthma). Symptoms are usually caused by common triggers such as infections, environmental exposures (smoke, allergens, etc.), medications (β-blockers, aspirin, NSAIDs), cold air, and exercise. Because symptoms of asthma may be intermittent, the physical examination is often normal. If spirometry is consistent with an obstructive pattern, then asthma can be differentiated from COPD by assessing the improvement in FEV1 after bronchodilator administration (e.g., albuterol); if FEV1 improves by at least 12%, then the diagnosis is more consistent with asthma. If spirometry is normal, as in this patient, a provocative test such as the methacholine challenge can be performed. Methacholine is a muscarinic agonist that will cause bronchoconstriction; asthmatics will be much more sensitive to lower doses of methacholine than the regular population and will develop an obstructive pattern on spirometry with a prolonged FEV1.
(A) This patient has normal findings on spirometry and therefore the administration of albuterol will not change the findings. (C) A chest x-ray would likely be normal in this patient. During an acute exacerbation, there may be hyperinflation of the lungs. (D) Allergen skin testing is not a bad idea, especially since the patient has a history of seasonal allergies and eczema, but it is not the best next step in management. (E) If the initial workup is negative, then the patient might be encouraged to measure peak expiratory flow or try a bronchodilator while symptomatic. Since he is undergoing spirometry already, a methacholine challenge should be attempted first to make the diagnosis.