A 14-year-old girl is brought to the office due to intermittent shortness of breath over the past 4 months. She is unable to link the episodes to specific events or exposures. The patient has no prior medical conditions and takes no medications. She does not smoke and has no second-hand tobacco exposure. Her family has a cat that remains indoors. There is no significant family history. Blood pressure is 110/65 mm Hg, pulse is 80/min, and respirations are 16/min. On physical examination, heart sounds are normal and the lungs are clear to auscultation. Lung function tests reveal a FEV1/FVC ratio of 83%. Which of the following would be most helpful in excluding a diagnosis of asthma in this patient?

Question

A 14-year-old girl is brought to the office due to intermittent shortness of breath over the past 4 months.  She is unable to link the episodes to specific events or exposures.  The patient has no prior medical conditions and takes no medications.  She does not smoke and has no second-hand tobacco exposure.  Her family has a cat that remains indoors.  There is no significant family history.  Blood pressure is 110/65 mm Hg, pulse is 80/min, and respirations are 16/min.  On physical examination, heart sounds are normal and the lungs are clear to auscultation.  Lung function tests reveal a FEV1/FVC ratio of 83%.  Which of the following would be most helpful in excluding a diagnosis of asthma in this patient?

Quizplus · Accepted Answer

Asthma is a disease of airway inflammation and bronchial hyperreactivity, with variable airflow obstruction that improves with bronchodilator medications. Classic symptoms include cough, shortness of breath, and wheeze, although these are nonspecific. Most patients with asthma have a chronic reduction in the FEV1/FVC ratio (≤70%; normal ~80%) due to increased expiratory airflow resistance. However, asymptomatic patients may have normal lung function tests, with alterations in lung function occurring only during exacerbations. This patient with intermittent shortness of breath has a normal FEV1/FVC ratio, therefore, further studies are required to exclude the diagnosis of asthma. Bronchial challenge testing is a highly sensitive test with high negative predictive value used to assess bronchial hyperreactivity and exclude asthma. A provocative stimulus (typically aerosolized methacholine, a cholinergic muscarinic agonist) is administered at increasing concentrations to induce bronchoconstriction. Patients with asthma are hyperresponsive to this stimulus and experience a decline in FEV1 at lower doses than nonasthmatics. However, the test is nonspecific and positive results may also be seen with chronic obstructive pulmonary disease, cystic fibrosis, and allergic rhinitis. (Choice A) Although peripheral eosinophil counts may be elevated in asthmatics, the presence of eosinophilia is not a sensitive or specific indicator of asthma and may be seen in other allergic diseases (eg, allergic rhinitis, drug reactions), parasitic infections (eg, strongyloides), and certain myeloid neoplasms. (Choice B) Most patients with asthma are sensitive to a variety of inhaled allergens, and in such patients, skin tests to various allergens will provoke a localized, immediate, type I hypersensitivity reaction. However, patients may have allergic disease without asthma and patients with nonallergic (intrinsic) asthma may not have allergies; therefore this test is not useful for diagnosing asthma. (Choice D) During an asthma attack, the lungs may appear hyperinflated on chest x-ray. However, chest x-rays are often normal between attacks; therefore, a chest x-ray cannot exclude asthma. (Choice E) Although serum IgE levels are generally elevated in patients with allergic asthma, patients with nonimmune-mediated asthma have normal levels of serum IgE. Intrinsic asthma can be precipitated by pulmonary infections (especially viral), aspirin ingestion, cold air, inhaled irritants (eg, perfumes), stress, and exercise. Educational objective: Bronchial challenge testing is a highly sensitive but nonspecific measure that can help exclude a diagnosis of asthma. A provocative stimulus (typically aerosolized methacholine) is administered at increasing concentrations to induce bronchoconstriction. Patients with asthma are hyperresponsive to this stimulus and experience a decline in FEV1 at lower doses than nonasthmatics.

A 14-Year-Old Girl Is Brought to the Office Due to Intermittent