Step 3. Establish work-relatedness: serial PEFR testing, augmented by serial FEV₁ or non-specific bronchial hyperresponsiveness testing.

• Cooperation of patient, the employer / company doctor / occupational health nurse.
• Changes in FEV₁ through the course of the working shift or after specific exposures (on site) = >10% decline in FEV₁ significant
• Remember - late (nocturnal) response may be overlooked

• Serial PEFR testing (if spirometry not possible):

  • PEFR at six different times each day, over a period of at least three weeks;
  • at least one week should be free of exposure (recommend sick leave for this period);
  • > 25% variability in PEFR significant.
  
  

• Non-specific bronchial hyperreactivity (histamine or methacholine challenge) changes with removal from and return to exposure at work - PC₂₀ £ 8 mg/ml or equivalent.

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