What are the key diagnostic criteria for identifying work-related asthma in a patient presenting with respiratory symptoms?

Key diagnostic criteria for identifying work-related asthma in a patient presenting with respiratory symptoms include:

• Taking a detailed clinical history focusing on the temporal relationship between symptoms and work exposure, specifically asking if symptoms are the same, better, or worse on days away from work, during holidays, weekends, or longer breaks from work. This helps identify a possible occupational component in adult-onset, poorly controlled, or recurrent asthma NICE NG245.
• Confirming asthma diagnosis with objective tests such as spirometry showing variable airflow obstruction, bronchodilator reversibility, or peak expiratory flow (PEF) variability of 20% or more measured twice daily over 2 weeks NICE NG245.
• Referral to an occupational asthma specialist for further assessment and confirmation, including consideration of specific inhalation challenge tests or serial PEF monitoring at and away from work NICE NG245; Baur et al. 2012.
• Excluding alternative diagnoses through clinical examination and investigations, as work-related asthma can mimic or coexist with other respiratory conditions NICE NG245; Bardana 1995.
• Supporting investigations may include skin prick testing or measurement of specific IgE to workplace allergens, blood eosinophil counts, and fractional exhaled nitric oxide (FeNO) to identify allergic sensitisation and airway inflammation consistent with asthma NICE NG245; Arnaiz & Kaufman 2002.

In summary, the diagnosis of work-related asthma relies on a combination of a suggestive clinical history linking symptoms to workplace exposure, objective confirmation of asthma, exclusion of other diagnoses, and specialist referral for occupational assessment and testing.