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. 2014 Jun 2;16(10):1348–1355. doi: 10.1093/ntr/ntu085

Table 1.

ROC Analysis: Sensitivity and Specificity of Expired CO Output (N = 662)

CO cutoff Sens Spec PPV NPV Eff False − (n)a False + (n)a
0 1 0 .94 .99 .944 0 37
1 .998 .108 .95 .8 .949 1 33
2 .99 .541 .97 .77 .965 6 17
3 .981 .811 .99 .71 .971 12 7
4 .957 .838 .99 .53 .950 27 6
5 .938 .838 .99 .44 .932 39 6
6 .907 .838 .99 .35 .903 58 6
7 .877 .865 .99 .29 .876 77 5
8 .85 .919 .99 .27 .854 94 3
9 .829 .946 1 .25 .836 107 2
10 .794 .946 1 .21 .802 129 2
11 .749 .973 1 .19 .762 157 1
12 .698 .973 1 .16 .713 189 1
13 .655 .973 1 .14 .673 216 1
14 .594 .973 1 .12 .615 254 1
15 .550 .973 1 .11 .573 281 1

Note. Bold and italic values correspond to ideal cut-off value. ROC = receiver operating characteristics; CO cutoff = carbon monoxide (CO) level in ppm used as cutoff to identify smokers (i.e., positive cotinine outcome); sens = sensitivity (i.e., proportion of smokers accurately identified; positive outcome); spec = specificity (i.e., proportion of nonsmokers accurately identified; negative outcome); PPV = positive predictive value (i.e., the percent of participants identified as smokers who are actually smokers); NPV = negative predictive value (i.e., the percent of participants identified as nonsmokers who are actually nonsmokers); eff = efficiency (i.e., weighted average of sensitivity and specificity taking into account disease prevalence); false − = false negatives (i.e., smokers mislabeled as “nonsmokers”); false + = false positives (i.e., nonsmokers mislabeled as “smokers”).

aActual smoking status: 37 nonsmokers (i.e., negative cotinine) and 625 smokers (i.e., positive cotinine).