A 38-year-old man is being evaluated for shortness of breath, cough, and chest tightness. He reports that his breathing "gets noisy" sometimes. The symptoms appeared 3 months ago, last throughout most of the day, and have gradually become more severe. The patient started working as a research laboratory technician 2 years ago, spending most of his day maintaining rodent colonies. He is unsure if his respiratory symptoms are related to his arrival at or departure from the animal facility. The patient's breathing improved when he attended a weeklong conference in another city. He reports no fevers, night sweats, weight loss, or unusual fatigue. Vitals signs are within normal limits. Pulmonary examination reveals normal lung sounds. Chest x-ray is normal. Baseline spirometry demonstrates normal airflow rates. Which of the following diagnostic tests will be most useful for establishing the diagnosis?

Question

A 38-year-old man is being evaluated for shortness of breath, cough, and chest tightness.  He reports that his breathing "gets noisy" sometimes.  The symptoms appeared 3 months ago, last throughout most of the day, and have gradually become more severe.  The patient started working as a research laboratory technician 2 years ago, spending most of his day maintaining rodent colonies.  He is unsure if his respiratory symptoms are related to his arrival at or departure from the animal facility.  The patient's breathing improved when he attended a weeklong conference in another city.  He reports no fevers, night sweats, weight loss, or unusual fatigue.  Vitals signs are within normal limits.  Pulmonary examination reveals normal lung sounds.  Chest x-ray is normal.  Baseline spirometry demonstrates normal airflow rates.  Which of the following diagnostic tests will be most useful for establishing the diagnosis?

Quizplus · Accepted Answer

11ec25c8_d102_a184_bc81_45ed113d66b2_MD0003_00 The patient has vague respiratory symptoms and an unremarkable initial workup (ie, normal examination, chest x-ray, and spirometry). However, his symptoms improved upon sustained absence (ie, 1-week conference) from the workplace. This key history element is suggestive of occupational asthma (OA), defined as asthma (ie, reversible airflow obstruction) as a result of workplace antigen exposure. Common antigens include animal proteins (eg, laboratory rodents), grain proteins or polysaccharides (eg, baking flours), and isocyanates (eg, paints, epoxies). At the onset of OA, patients may link their symptoms closely to the workplace. When airway inflammation becomes chronic, however, the symptoms may persist throughout the workweek and abate only after prolonged absence (days to weeks). Due to differences in levels of persistent airway irritation, physical examination, chest imaging, and spirometry may be normal despite the presence of symptoms. Therefore, clinical suspicion for OA rests upon diligent occupational history and symptom query. OA is diagnosed by demonstrating workplace-specific changes in airway physiology. This can be established through serial peak expiratory flow rate measurement (eg, ≥4 times daily, >2-week period) demonstrating decline by ≥20% at the workplace relative to at home. Patients should be counseled to maintain a concurrent symptom diary. Other diagnostic tactics include in-workplace spirometry, serial methacholine bronchoprovocation testing, and serial sputum eosinophil count. Patients diagnosed with OA should be counseled to seek alternate employment whenever possible. (Choice A) Allergic bronchopulmonary aspergillosis can cause refractory asthma. However, it presents with radiographic opacities (eg, bronchiectasis and mucus plugging), productive cough with tenacious sputum, and constitutional symptoms (eg, low-grade fever, malaise). (Choice B) Acute occupational hypersensitivity pneumonitis can present with respiratory symptoms waxing and waning with workplace exposure. However, the chest x-ray demonstrates ground glass opacities (reflecting alveolitis), spirometry reveals restriction or a mixed pattern, and constitutional symptoms are common. (Choice C) Vocal cord dysfunction (ie, paradoxical inspiratory adduction) can present with dyspnea and noisy breathing (stridor). However, it tends to affect young women, attacks occur in paroxysms (instead of lasting daylong), and spirometric flow-volume loop abnormalities would be expected. (Choice E) Allergic rhinitis with postnasal drip can produce cough with no obvious physiologic abnormalities. However, nasal and sinus symptoms would be expected, and cough would not be expected to remit upon absence from the workplace. Educational objective: Occupational asthma (OA) is induced by workplace antigen exposure (eg, animal proteins, flours, isocyanates). Chronic OA may result in persistent airway inflammation that abates only after prolonged absence. OA is diagnosed by demonstrating workplace-specific declines in airway physiology, such as impaired peak expiratory flow rate.

A 38-Year-Old Man Is Being Evaluated for Shortness of Breath