Table 1.
Demographic, occupational and clinical characteristics of the participants
| Positive SIC (n=17) | Negative SIC (n=27) | p Value | |
|---|---|---|---|
| Gender (female) | 13 (76) | 23 (85) | 0.466 |
| Age, years* | 47 (39–49) | 47 (35–53) | 0.942 |
| Referral by WCB | 13 (76) | 20 (74) | 0.858 |
| Job/industry | |||
| Professional cleaners | 9 | 15 | |
| Healthcare facilities | 2 | 5 | |
| Various industries | 3 | 4 | |
| Private houses | 1 | 3 | |
| Public buildings | 2 | 2 | |
| Kitchens | 1 | 1 | |
| Healthcare workers | 7 | 9 | |
| Food workers | 1 | 2 | |
| Pharmaceutical workers | 0 | 1 | |
| Exposure to respiratory sensitisers | 16 (94) | 16 (59) | 0.033 |
| QAC | 10 | 6 | |
| QAC and glutaraldehyde | 1 | 3 | |
| Glutaraldehyde | 3 | 7 | |
| Ethanolamines | 2 | 0 | |
| No identified sensitiser | 1 | 11 | |
| Current and ex-smokers | 6 (35) | 8 (30) | 0.694 |
| Atopy† | 7 (41) | 13 (48) | 0.651 |
| Asthma pre-existing to exposure | 2 (12) | 2 (7) | 0.624 |
| Duration of exposure before the onset of asthma, months* | 12 (5–153) | 53 (31–165) | 0.114 |
| Duration of asthma before SIC, months* | 25 (7–59) | 25 (10–55) | 0.980 |
| Delay since last work exposure, months* | 10 (0.3–16) | 8 (0.1–24) | 0.808 |
| Work-related respiratory symptoms | |||
| Wheezing | 14 (82) | 14 (52) | 0.056 |
| Breathlessness | 14 (82) | 20 (74) | 0.716 |
| Cough | 11 (65) | 21 (78) | 0.343 |
| Chest tightness | 11 (65) | 18 (67) | 0.893 |
| Sputum | 4 (24) | 8 (30) | 0.740 |
| Work-related rhinitis | 8 (47) | 16 (59) | 0.429 |
| Work-related dermatitis | 5 (29) | 5 (19) | 0.401 |
| Inhaled corticosteroid | |||
| Number with inhaled corticosteroid | 13 (76) | 15 (56) | 0.160 |
| Low dose‡ | 3 (18) | 5 (19) | |
| Medium dose‡ | 5 (29) | 5 (19) | 0.494 |
| High dose‡ | 5 (29) | 5 (19) | |
| Short-acting β2-agonist≥once a day | 7 (41) | 1 (4) | 0.002 |
| Baseline FEV1,% predicted* | 92 (73–101) | 100 (88–109) | 0.049 |
| Baseline FEV1/FVC, %* | 71 (63–77) | 80 (73–83) | 0.002 |
| Baseline airway obstruction§ | 5 (29) | 1 (4) | 0.016 |
Data are presented as n (% of available data) unless otherwise specified.
*Median value with 25th–75th IQR in parentheses.
†Atopy defined by a positive skin-prick test to at least one common inhalant allergen.
‡Low dose: equal or less than 500 µg beclomethasone dipropionate equivalent/day; medium dose: more than 500 µg but equal or less than 1000 µg/day; and high dose: more than 1000 µg/day.
§Airway obstruction defined by an FEV1 <80% predicted value and an FEV1/FVC ratio <70%.
FEV1, forced expiratory volume in one-second; FVC, forced vital capacity; PC20, provocative concentration of histamine causing a 20% fall in FEV1; QAC, quaternary ammonium compound; SIC, specific inhalation challenge; WCB, workers' compensation board.