The primary physiologic manifestation of airways hyperresponsiveness is variable or reversible airflow obstruction. Airflow changes can occur spontaneously, with treatment, with a precipitating exposure, or with diagnostic maneuvers such as nonspecific inhalation challenge. Work-related changes in medication requirements can accompany these symptom patterns. Workplace exposure to an agent previously associated with occupational asthma. Positive response to specific inhalation challenge testing with an agent to which the patient has been exposed at work.
Many agents can induce occupational asthma via a specific hypersensitivity mechanism.
A comprehensive list of these asthma inducers is used for this criterion. Cross-shift spirometry testing on multiple days might help confirm the association with work. Alternatively, PEFR can be measured serially throughout the day on multiple days at and away from work using a portable peak flow meter. Specific inhalation challenge testing is potentially dangerous and should be performed by experienced personnel in a hospital setting where resuscitation facilities are available and frequent observations can be made over sufficient time to monitor for delayed reactions. Specific inhalation challenge testing is usually not necessary for clinical diagnosis of occupational asthma.