Occupational asthma caused by toluene di-isocyanate (TDI) in a polyurethane foam factory worker is best characterised by which feature that distinguishes it from non-occupational asthma?
- A Improvement in FEV1 >12% with bronchodilator
- B Peripheral blood eosinophilia >500 cells/μL
- C Symptoms worsen on work-days and improve during weekends and vacations ✓
- D Presence of serum-specific IgE against TDI
Explanation
The hallmark of occupational asthma is the work-relatedness of symptoms: worsening on work days (especially towards the end of the shift or in the evening) and improvement during weekends, public holidays, and vacation periods — the 'temporal work-related pattern.' Specific IgE may be absent in irritant-induced TDI asthma (sensitiser vs. irritant mechanisms). Bronchodilator reversibility and eosinophilia are features of asthma in general, not specific to occupational origin. Serial PEF monitoring showing this temporal pattern is the standard diagnostic approach.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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