2 BIOCHEMICAL MARKERS EFFECTIVELY USED TO SEPARATE SMOKELESS TOBACCO USERS FROM SMOKERS AND NONUSERS

Data from asbestos workers were used to devise a cutpoint classifier t o identify subjects as Nonuser (non-tobacco user), Smokeless (exclusiv e smokeless tobacco user), and Smoker (ignited tobacco user). In some clinical trials and smoking cessation programs, Smokeless should be se parated from Smoker. One therefore needs a marker for smoke exposure, such as thiocyanate, since nicotine levels, as measured by cotinine, c ould be similar in both groups. Levels of cotinine (ng/mL) and thiocya nate (mu mol/L) levels (mean +/- SD) were, respectively: 320.9 +/- 201 .1 and 145.9 +/- 63.7 for the Smoker group; 339.1 +/- 327.5 and 32.0 /- 16.9 for the Smokeless group; and 0.6 +/- 2.6 and 58.2 +/- 33.2 for the Nonuser group. For Nonuser, Smokeless, and Smoker, respectively, the self-reported status was 45.1%, 10.8%, and 44.1%, which was adjust ed to 42.2%, 11.6%, and 46.2%; the classifier yielded sensitivities of 100%, 76.1%, and 92.2%; specificities of 96.1%, 97.6%, and 96.4%; and predictive values of 94.9%, 80.6%, and 95.6%. The classifier successf ully identified Nonusers, separated Smokeless from Smoker, and determi ned the prevalence of false reports in our cohort.