Table 2—

Results of pre-/postchallenge histamine reactivity, bronchial challenge and occupational asthma system (OASYS)-2 score

CasePrevious histamine PD20 µmolPrechallenge histamine PD20 µmolPostchallenge histamine PD20 µmol% Maximum immediate fall in FEV1% Maximum late fall in FEV1OASYS-2 score
3>8Not doneNot done−14 work challengeNot doneSee text
4>4800 µg methacholine125 µg methacholine70 µg methacholine−15 (NCl3) −41 (formaldehyde)0 (NCl3) −4.1 (formaldehyde)4.00
  • #: The prechallenge histamine test was performed within 2 days of being at work in case 3, but in case 2 the worker had relocated to a library 1-yr previously. The worker previously had a positive histamine challenge when seen in the clinic whilst working as a lifeguard (2 days prior to the test) with a provocative dose causing a 20% fall in the forced expiratory volume in one second (FEV1) (PD20) of 1.5 µmol

  • : The worker had two challenges to nitrogen trichloride with 30 min exposure on consecutive days. The data shown in the table are for the second day following a 30-min exposure. On the first day, the maximum immediate reaction fall in FEV1 was −17% at 20 min and maximum late reaction at 40 min was −15.