Asthma USMLE Step 1 Practice Question
A 32-year-old man presents with a 3-month history of progressive dyspnea on exertion. He denies chest pain, fever, or recent infections. Vital signs are normal. Chest examination reveals end-expiratory wheezing bilaterally. Spirometry shows FEV1 of 78% predicted with an FEV1/FVC ratio of 0.68. To evaluate for asthma, the patient undergoes methacholine bronchoprovocation testing. Which of the following results would be most consistent with asthma?
Answer choices
- AFEV1 decreases by 8% at the maximum methacholine concentration of 16 mg/mL
- BFEV1 decreases by 22% at a methacholine concentration of 4 mg/mLCorrect answer
- CFEV1 increases by 15% following inhaled albuterol
- DDiffusion capacity (DLCO) is 125% of predicted with normal FEV1
- EPeak flow variability of 12% between morning and evening measurements over 2 weeks
- FReversible airflow obstruction with 20% FEV1 improvement post-bronchodilator
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