Correlation between urinary nicotine, cotinine and self-reported smoking status among educated young adults

The objective of this study was to correlate, differentiate and validate the self-reported smoking status of educated young adults with urinary biomarkers (i.e. nicotine and cotinine). Freshmen students were recruited on voluntary basis. They filled-up self-administered questionnaire and their urine samples were collected for analysis. The urinary nicotine (UN) and cotinine (UC) were measured by gas chromatograph–mass spectrometry. Smokers, non-smokers and ex-smokers were found to be both significantly correlated and different in their UN and UC levels. UC level of 25 ng/ml was the optimal cut-off to differentiate smokers from non-smokers. Using this cut-off value, the prevalence of smoking among the students was found to be higher (15.4%) than the self-reported data (14.3%). UC is useful in validating individual recent smoking history and the cut-off could serve as a marker for assessing the clinical impact of smoking and environmental tobacco smoke (ETS) exposure on human health.