Medical surveillance for occupational asthma-how are cases detected?

In Finland, medical surveillance, including spirometry, is periodically performed for workers who are exposed to agents capable of causing occupational asthma (OA). Although it has been shown that surveillance can detect OA at an early stage, few studies have assessed its benefits or the role of surveillance spirometry.

To assess the role of surveillance and spirometry in detecting OA and to evaluate the quality of spirometry.

We retrospectively reviewed the medical files of patients in health surveillance programmes who were diagnosed with sensitizer-induced OA at the Finnish Institute of Occupational Health in 2012‒14. We collected information on work exposure, respiratory symptoms, healthcare visits that initiated the diagnostic process, first spirometry and other diagnostic tests.

Sixty files were reviewed. Medical surveillance detected 11 cases (18%) and 49 cases (82%) were detected at doctors' appointments that were not related to surveillance. The median delay from the onset of asthma symptoms to diagnosis was 2.2 years. Delay did not differ between these groups. No cases were detected on the basis of abnormal spirometry without respiratory symptoms. However, five patients (8%) initially reported solely work-related rhinitis symptoms. Spirometry was normal in half of the cases and quality criteria were fulfilled in 86% of the tests.

Fewer than one in five OA cases were detected through medical surveillance. Investigations were initiated by respiratory symptoms. No asymptomatic worker was referred because of abnormal spirometry. Our results highlight the importance of work-related nasal symptoms in detecting OA.