Saliva cotinine and thiocyanate: chemical indicators of smokeless tobacco and cigarette use in adolescents. 
Recent attempts to measure smoking behavior using chemical tests may have been confounded by the use of smokeless tobacco.  An objective measure of smokeless tobacco use is needed, particularly among adolescents who may not provide accurate self-reports of tobacco usage.  Saliva cotinine was used to distinguish self-reported tobacco users from nonusers and a combination of saliva cotinine and thiocyanate (SCN) tests was used to distinguish smokers from smokeless tobacco users.  The subjects were 471 students in grades 7 through 11 who lived in a high-tobacco production area.  Approximately 89% of reported nonusers had no detectable cotinine and 99% of nonusers had levels less than 25 ng/ml.  Of those who had used tobacco within the last 12 hr, 95% had detectable levels of cotinine.  Samples that tested positive for cotinine were also tested for SCN.  Eighty-six percent of smokers and 74% of mixed users had SCN values of greater than 1000 mumol/liter, while only 14% of smokeless users had SCN values at that level.  The combination of cotinine and SCN was effective in distinguishing smokers from smokeless users but was not effective in distinguishing mixed use from the other two types of use.