16th January 2024

Diagnosis

The diagnosis of OA relies on careful history-taking in order to help identify key risk factors such as atopy, smoking and exposure to sensitising agents and irritants. The following investigations help to support a diagnosis of OA.

Serial peak expiratory flow rate (PEFR) measurements

• This is the first-line investigation for OA
• Standard guidelines recommend PEFR measurements at least four times daily (equally spaced) over a period of at least three weeks
• PEFR measurements should be recorded alongside work tasks and any exposures 
• In work-related diseases, there will be an increase in diurnal variability of PEFR. 

Spirometry (pre- and post-bronchodilator)

• Values may be normal; however, this is useful as it provides a baseline for any future investigations.
• An increase in FEV1 and/or FVC of over 12% following bronchodilation confirms reversible airflow obstruction. This confirms the diagnosis of asthma.

Blood tests

• Specific serum IgE assays- These detect specific IgE antibodies to workplace allergens and can thus confirm sensitisation.