Clinical evaluation of occupational asthma.

In this paper, the procedures in the assessment of occupational asthma (OA) are discussed. Only the most common subtype of OA is considered here, i.e. that in which symptoms appear after a latency period from the beginning of exposure. OA is characterized by variable bronchial obstruction, and variable bronchial hyperresponsiveness caused by specific agents inhaled at work. The clinical investigation of OA is a stepwise approach which includes a comprehensive history together with physiological and immunological studies. The first step is to identify symptoms and relate exposure at work to the presence in the workplace of substances known to provoke OA. The presence of bronchial asthma must then be confirmed; this is achieved by assessing the reversibility of bronchial obstruction and/or the presence of nonspecific bronchial hyperreactivity and/or the presence of significant peak expiratory flow (PEF) variability. The relationship between work and symptoms may first be assessed by means of serial measurements of PEF and of nonspecific bronchial hyperreactivity during periods at work and away from work. When the suspected agent is a high-molecular-weight (HMW) or a low-molecular-weight (LMW) agent known to act through an immunoglobulin E (IgE)-mediated mechanism, skin tests and/or research for specific IgE should be performed. In case of sensitization, where a relationship between asthma and work has been demonstrated by means of serial monitoring of PEF, a diagnosis can be made. If the suspected agent is a LMW agent, a specific inhalation challenge test in the laboratory or at the workplace is necessary.