Question 2. When should you suspect occupational asthma?

From Chapter 8 of the Philippine Consensus Report on Asthma 2004 by the Philippine College of Chest Physicians.
This guideline starts below.

When should you suspect occupational asthma?

Answer

An occupational cause should be considered for all new cases of asthma in adults.

A detailed occupational history of past and current exposure to possible causal agents in the workplace, work processes and specific job duties should be obtained. A history of asthma beginning during a working lifetime should lead to consideration of occupational asthma. The classic history is one of a worker whose asthma is worse at work, with improvement during weekends or holidays. However, this pattern may often be absent because symptoms are also usually present outside the workplace, being triggered by exposure to irritants such as cold air, fumes or exercise.

Questionnaires, although sensitive and essential in the assessment, are not specific tools. In a study on workers suspected to have occupational asthma, the predictive value of a positive questionnaire was 63% and a negative questionnaire was better at 83%. Another study showed that clinical history has a high sensitivity of 96% but a low specificity of 25% for the diagnosis of occupational asthma.