Figure 2.

Comparisons of the ROC curves of the tobacco-specific biomarkers used to distinguish the active smoking behavior. Urine creatinine can be used to calculate the urine NNAL/creatinine ratio, which is an adjusted indicator of NNAL. The sensitivity and specificity values at the optimal cut-off points were as follows: urine NNAL, 99.60% and 86.70%, respectively; urine NNAL/creatinine, 97.50% and 90.20%, respectively; and serum cotinine, 98.30% and 91.60%, respectively. Data obtained from the National Health and Nutrition Examination Survey (2007–2012), National Center for Health Statistics. AUC, area under the curve; NNAL, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanonol; ROC, receiver operating characteristic.