Urine cotinine levels by self-reported smoking status in November 2017, N=202
| Self-reported smoking status* | Age, mean (SD) (years) | N (%) | Cotinine levels (ng/mL)† | ||||
| Median (IQR) | P value‡ | Cotinine >50 ng/mL, N (%) | Cotinine ≤50 ng/mL, N (%) | P value‡ | |||
| All participants | 29 (8) | 202 (100%) | <LOD (<LOD, 106.75) | 68 (34) | 134 (66) | ||
| Current smoker | 30 (8) | 24 (12%) | 310.03 (76.23, 650.58) | <0.01 | 19 (79) | 5 (21) | <0.01 |
| Former smoker | 32 (9) | 28 (14%) | 7.84 (<LOD, 92.98) | 10 (36) | 18 (64) | ||
| Never smoked | 28 (8) | 150 (74%) | <LOD (<LOD, 63.34) | 39 (26) | 111 (74) | ||
Sensitivity: 19 true positive smokers/(19+10+39)×100=28%.
Specificity: 129 true negative former and never smokers/(5+18+111)×100=96%.
*November survey question: ‘do you smoke cigarettes?’.
†Values above 5000 ng/mL were put at 5000 ng/mL. LOD: 5 ng/mL.
‡P value for overall difference between smoking groups.
LOD, limit of detection.