A 39-year-old man is evaluated on a Wednesday for intermittent shortness of breath, cough and chest tightness. He denies fever or chills, sputum production, heartburn or other gastrointestinal symptoms. He currently works in a hardware store where he manages the carpentry and woodcutting department. He is concerned his symptoms may be associated with his work. He works 5 days a week including weekends. His usual days off from work are Monday and Tuesday. He is otherwise healthy and takes no medications, doesn’t drink alcohol and has never smoked. He doesn’t usually wear cologne.
On physical examination, vital signs are normal. BMI is 25.4 and stable. Oxygen saturation breathing ambient air is 99%. The cardiac exam is normal. His lungs are clear, with no wheezing or crackles, dullness to percussion and has good excursion. The remainder of the examination is unremarkable.
His chest radiograph and spirometry are normal.
What is the next best step in management?
A. High-resolution chest CT
B. Methacholine challenge test
C. Recommend changing to a different job
D. Repeat spirometry after workplace exposure
E. Inhaled glucocorticoid daily
Correct answer:D – Repeat spirometry after workplace exposure
Key Point: Occupational asthma is symptomatic mainly during exposure to the workplace specific allergen and will improve after avoidance of this trigger. Diagnosis can therefore be aided by spirometry before and after exposure to the workplace environment.
Discussion: Occupational asthma is due to exposure to specific environmental triggers that occur in the workplace and may occur in up to 15% of patients with asthma. The symptoms of occupational asthma involve the usual problem of airway hyperreactivity and include dyspnea, wheezing, cough and chest tightness.
Diagnostic workup involves tests to investigate and rule out asthma mimics or alternative problems. A chest radiograph and spirometry are good initial choices. When these are unrevealing other tests may help such as repeat peak expiratory flow rates during workplace exposure, or as in this case, repeat spirometry during or just after workplace exposure. This patient is likely triggered by sawdust from one or more specific species of tree.
A high resolution CT scan of the chest is premature in this patient who likely has occupational asthma. While a methacholine challenge test may help identify the diagnosis in patients with intrinsic asthma, it may not help in patients with specific asthma such as this.
Changing jobs is a possible treatment option for patients with occupational asthma but this should only be recommended after the diagnosis is confirmed. Additionally, the patient may be advised to attempt to change workplace location within the same job prior to leaving the job altogether.
Inhaled glucocorticoids may also be used for occupational asthma once the diagnosis is confirmed.
PMID: 24521110