Associations between SHS exposure (defined using self-report and measured plasma cotinine (>0.05 ng/mL or above the limit of quantification if higher than 0.05 ng/mL)) and asthma outcomes
| Asthma outcomes | OR (95% CI) | |
| Self-reported exposure* | Plasma cotinine determined exposure | |
| Asthma exacerbations in the previous 12 months† | 1.08 (0.75 to 1.57) | 1.40 (1.03 to 1.89) |
| Hospitalisations | 1.77 (0.79 to 3.95) | 1.26 (0.60 to 2.67) |
| ER visits | 1.21 (0.70 to 2.09) | 1.07 (0.65 to 1.75) |
| Oral steroid prescription | 1.00 (0.71 to 1.41) | 1.54 (1.18 to 2.04) |
| Asthma control (binary outcome)‡ | 1.62 (1.09 to 2.38) | 1.53 (1.12 to 2.13) |
| Not well controlled versus controlled | 1.43 (0.93 to 2.21) | 1.39 (0.98 to 1.98) |
| Very poorly controlled versus controlled | 1.79 (1.18 to 2.70) | 1.67 (1.18 to 2.36) |
*Self-reported exposure to SHS was determined as any versus no reported current smokers in the household.
†Asthma exacerbations assessed as a combined variable for any exacerbations (hospitalisations, ER visits, prescription of oral steroids) versus none.
↵‡Asthma control assessed as binary outcome with a combined ‘not well controlled’ and ‘very poorly controlled’ category compared with controlled asthma.
ER, emergency room; SHS, secondhand smoke.