Differentiating between smokers and nonsmokers using serum cotinine

Our goal is to evaluate implications of cotinine cut points in subgroups of smokers and nonsmokers. Data were assessed from 13,357 adult participants and collected over a period of 6 years by the National Health and Nutrition Examination Survey (2009–2014). Receiver operating characteristic curve analysis was used to identify optimal cut points. Rao–Scott χ tests measured associations between group characteristics. The optimal serum cotinine cut point adult cigarette smokers was 3.63 ng/ml (sensitivity of 96.7%; specificity of 93.0%). This cut point differed by gender as well as race/ethnicity. There are notable differences in subgroup cut points compared with previous research. Use of gender or race/ethnicity specific cut points is more appropriate when feasible and may help clinician recommendations.