Clinical criteria for the diagnosis:
(1) A documented absence of preceding respiratory complaints.
(2) The onset of symptoms after a single exposure incident or accident.
(3) The exposure was to a gas, smoke, fume or vapor which was present in very high concentrations.
(4) The exposing agent has irritant qualities to its nature.
(5) The onset of symptoms occurred within 24 hours after the exposure.
(6) Symptoms persisted for at least 3 months.
(7) Symptoms simulated asthma with cough, wheezing, and dyspnea predominating.
(8) Pulmonary function tests show airflow obstruction (reduced FEV1-to-FVC ratio, reduced FEF25-75).
(9) Methacholine challenge testing is positive.
(10) Other types of pulmonary diseases have been ruled out.
Predisposing factors:
(1) accidental exposure, usually in a workplace
(2) poor ventilation with limited air exchange in the area
Features different from occupational asthma:
(1) absence of a preceding period of sensitization
(2) onset of illness after a single, first-time exposure
NOTES:
(1) A person with a pre-existing lung disease can develop the syndrome but it is just harder to be certain about the diagnosis.
(2) Initial chest X-rays are typically negative.
(3) Chronic airways disease and long-term sequelae may occur.
