Occupational asthma: a practical approach.

Although evaluation of possible occupational asthma may be complex, it can be pursued systematically by first assessing whether asthma is present, and then determining whether asthma is caused or triggered by the workplace or by alternative or confounding nonoccupational explanations. A detailed history is of great importance in raising suspicion of occupational asthma, but studies have shown that even detailed histories obtained by experienced specialists can lead to inaccurate conclusions about the presence or absence of occupational asthma. Consequently, objective measurements should be performed to establish the diagnosis of occupational asthma whenever possible. If the patient is still working in the workplace, work-related changes in spirometry or peak flow measurements can confirm the diagnosis. For occupational asthma from some airborne sensitizers, immediate-type skin testing or in vitro tests for specific IgE may establish sensitization. However, there is evidence that for some isocyanates, in vitro tests for specific IgG serum antibody levels correlate better with documented bronchospasm from isocyanate exposure, even though the IgG antibody is not thought to be pathogenic. Controlled, specific inhalation tests may be valuable, but they should be performed only under experienced medical supervision. Intervention should be focused on reducing or avoiding harmful workplace exposures so that permanent lung impairment and need for chronic medical treatment are avoided. Assessment of permanent impairment/disability from occupational asthma optimally should be determined 2 years after the removal from occupational exposure, when improvement has been shown to plateau and the patient will likely have reached maximal medical improvement.