| All | High activity | Low activity | |
| Centres n | 24 | 12 | 12 |
| SIC used | |||
| Systematically to confirm occupational asthma | 9 (38) | 6 (50) | 3 (25) |
| Only if other tests are inconclusive | 14 (58) | 6 (50) | 8 (67) |
| Number of SIC annually | 12.2 (0.3–124) | 25.0 (12–124) | 8.0 (0.3–12.0) |
| Dedicated# facilities for SIC | 21 (88) | 11 (92) | 10 (83) |
| Physician oversees SIC | 24 (100) | 12 (100) | 12 (100) |
| Nurse performs SIC | 16 (67) | 8 (67) | 8 (67) |
| Hygienist, chemist or technician involved in SIC | 13 (54) | 7 (58) | 6 (50) |
| Informed consent from patient | 19 (79) | 10 (83) | 9 (75) |
| Patients routinely admitted to hospital | 13 (54) | 8 (67) | 5 (42) |
| Inhaled steroids stopped prior to SIC¶ | 22 (92) | 11 (92) | 11 (92) |
| Control exposure used | 23 (96) | 12(100) | 11 (92) |
| Simulation of work tasks | 20 (83) | 10 (83) | 10 (83) |
| GenaSIC+ or comparable device | 5 (21) | 3 (25) | 2 (17) |
| Different doses of active agent used on same day | 15 (63) | 7 (58) | 8 (67) |
| Different active agents used on same day | 4 (17) | 4 (33) | 0 (0) |
| FEV1 as primary outcome | 21 (88) | 11 (92) | 10 (83) |
| NSBHR routinely used as an outcome parameter | 17 (71) | 9 (75) | 8 (67) |
| Sputum cytology used as an outcome parameter | 11 (46) | 8 (67) | 3 (25) |
| FeNO used as an outcome parameter | 16 (67) | 8 (67) | 8 (67) |
| SIC with low molecular weight agents in the past 3 years | 822 (51) | 693 (51) | 129 (50) |
| Percentage of SIC with excessive asthmatic response | 0 (0–18) | 2 (0–6) | 0 (0–18) |
Data are presented as n (%) or median (range), unless otherwise stated. SIC: specific inhalation challenge; FEV1: forced expiratory volume in 1 s; NSBHR: nonspecific bronchial hyperreactivity; FeNO: exhaled nitric oxide fraction. #: enclosed and ventilated chamber reserved for SIC; ¶: inhaled steroids were stopped prior to SIC always or when possible; +: GenaSIC (SCL Medtech, Montréal, QC, Canada) is a closed-circuit chamber that facilitates the production of aerosols at steady concentrations.