Validation of subjects statements as compared with expired carbon monoxide, in a sub-sample of the population
| Strategy A | Strategy B | |
| Comparison between self reported smoking status and expired CO ⩾7 ppm | ||
| At inclusion, in the whole population | ||
| Number | 612 | 285 |
| Concordance | 0.82 | 0.79 |
| κ coefficient (95% CI) | 0.61 (0.54, 0.67) | 0.56 (0.46, 0.65) |
| At one year follow up, among subjects who were smokers at inclusion | ||
| Number | 164 | 67 |
| Concordance | 0.82 | 0.76 |
| κ coefficient (95% CI) | 0.38 (0.20, 0.56) | 0.37 (0.12, 0.62) |
| Among smokers, correlation between expired carbon monoxide and number of cigarettes/day3-150 † | ||
| Inclusion | ||
| Number | 205 | 98 |
| r | 0.57 | 0.51 |
| p | p=0.0001 | p=0.0001 |
| One year follow up | ||
| Number | 142 | 49 |
| r | 0.54 | 0.57 |
| p | p=0.0001 | p=0.0001 |
↵3-150 Given the skewness of the distribution, cigarette consumption was log transformed. †The consumption of occasional smokers (<1 cig/day) was arbitrarily fixed at 0.2 cigarettes/day as many occasional smokers reported smoking 1 cig/week.