Table 1– Key messages for performing and interpreting specific inhalation challenge (SIC) with occupational agents
General safety requirements, contraindications and precautions should be strictly applied in order to minimise the risk of severe adverse events
The duration or concentration of exposure to occupational agents should only be gradually increased under close monitoring of functional parameters
A control challenge test with a 6–8 h period of spirometric monitoring on a separate day is required for the interpretation of the SIC results
Changes in FEV1 should be the primary physiological outcome measure, but other functional indices (i.e. airway resistance/conductance) may be useful in subjects who are not able to complete reproducible expiratory manoeuvres
NSBHR should be measured at least before the SIC and at the end of a negative SIC procedure. A significant increase in post-challenge NSBHR provides further evidence for a positive response when changes in FEV1 are indeterminate and indicates that additional challenges are necessary before excluding a diagnosis of occupational asthma
Sputum eosinophils and FeNO may help interpret equivocal tests and indicate the need for longer SIC exposures to reduce the risk of false-negative results
  • FEV1: forced expiratory volume in 1 s; NSBHR: nonspecific bronchial hyperresponsiveness; FeNO: exhaled nitric oxide fraction.