Differentiating between smokers and nonsmokers using serum cotinine

Aim: Our goal is to evaluate implications of cotinine cut points in subgroups of smokers and nonsmokers. Materials & methods: 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 χ² tests measured associations between group characteristics. Results: 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. Conclusion: 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.