Urinary cotinine concentrations in healthy controls with different levels of active or passive tobacco smoke exposure
| Cut-off ng·mL−1 | |||
| Patients | Smokers | Exposed nonsmokers | |
| Heavy versus light (actual smokers or SHS) | 327 | 2100 | 170 |
| Heavy smokers versus unexposed nonsmokers | 327 | NA | 50 |
Heavy and light smokers, heavily and lightly exposed nonsmokers, and lightly exposed and non-exposed non-smokers were compared. SHS: second-hand smoke; NA: not available. Data from [15].