Critical Aspects of the History of Occupational Asthma
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Critical Aspects of the History of Occupational Asthma Susan M. Tarlo, MB, BS, FRCP(C)
Abstract The medical history is the gateway to the diagnosis of occupational asthma. The medical history should indicate whether a patient’s asthma began during a work period and whether the asthma worsens during work periods or improves on days when the patient is off work or on holidays. A suspicion of sensitizer-induced occupational asthma will increase if the patient was exposed to a recognized respiratory sensitizer in the workplace at the time of the onset of symptoms or if the patient had associated symptoms of allergic rhinitis and conjunctivitis. A history of accidental high respiratory irritant exposure shortly before the initial onset of symptoms would raise the possibility of irritant-induced occupational asthma. Although such features of the history are sensitive indicators of occupational asthma, they are not specific and should therefore be followed by further investigations to confirm the diagnosis of asthma and its relation to the workplace exposure. The earlier the diagnosis is suspected and investigated, the better the outcome is likely to be for the patient.
The best medical outcome for those with OA related to a sensitizer is associated with removal from further exposure to the sensitizer, especially early after the onset of symptoms and when the asthma is relatively mild.5 Nevertheless, the diagnosis can result in very significant socioeconomic effects, even with appropriate workers’ compensation support.6 An accurate and early diagnosis is therefore of great importance, to allow a better medical outcome and to facilitate early relocation within the same company or retraining to give the worker the best chance for reentry at another workplace. Unfortunately, there are often delays in the diagnosis of OA, and the diagnosis may not be reached until several years after the onset of symptoms.7 A recent chart review at an occupational lung clinic in Ontario showed a mean time to diagnosis of over 3 years. Delayed suspicion of work-related asthma by the primary care physician was related to the patient’s fear of losing work and to a lack of inquiry by the physician about the relationship of the asthma to the patient’s work.7 Lower income and education levels were also associated with a longer time to diagnosis.
Occupational asthma (OA) is defined as asthma that is due to causes and conditions attributable to a particular occupational environment and not to stimuli encountered outside the workplace.1 It has been estimated to account for 10 to 15% of all adult-onset asthma.2 It is most often caused by sensitization to a workplace substance (via immunoglobulin E [IgE] antibody responses or other immunologic mechanisms) but can also be due to high-level irritant exposure in about 5% of all cases (irritant-induced asthma,3 of which the clearest example is reactive airways dysfunction syndrome [RADS]4). This article will not discuss work-aggravated asthma, which is the aggravation of underlying asthma by factors in t
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