The most appropriate next step in management is to repeat spirometry after workplace exposure. Occupational asthma, related to workplace exposures to agents associated with airway hyperreactivity, should be suspected in all adults with a diagnosis of asthma because it may be a primary target for treatment. It should also be suspected in patients with asthma-like symptoms that vary with exposure to the workplace, as in this patient. This patient has likely been exposed to diisocyanates from spray painting in the auto body shop where he works, which are associated with triggering bronchospasm. Early recognition of an association of asthma symptoms with potential workplace exposure, and testing if indicated, is important for diagnosis and to guide therapy. Serial monitoring of peak flows throughout the workday, with comparison to a baseline time period away from exposures, can be helpful to support the diagnosis. Similarly, spirometry before and after rechallenge with workplace exposures is helpful to confirm the diagnosis. Because of the possibility that this patient's occupational exposure may be responsible for his asthma symptoms, it is appropriate to perform spirometry before and after exposure to the potential causative agent. If documented, treatment of occupational asthma should follow guidelines for typical asthma, and allergen exposure should be controlled or eliminated if possible. If significant changes in spirometry are not seen post workplace exposure and a suspicion for any underlying asthma remains, a methacholine challenge test may be appropriate.
Advising a change in workplace venue to avoid allergen exposure for occupational asthma would be premature because the diagnosis has not been confirmed.
High-resolution chest CT is indicated for evaluation of suspected parenchymal lung disease. However, this patient's symptoms are most consistent with airways disease, and he has no clinical evidence of a parenchymal process. Therefore, this testing would not be expected to be of benefit.
Empiric therapy for asthma without documentation of the diagnosis or an association of his asthma symptoms with workplace exposure would not be appropriate.