OBJECTIVE: To assess the optimal cut-point for salivary cotinine concentration to identify smoking status in the adult population of Barcelona. METHODS: We performed a cross-sectional study of a representative sample (n=1,117) of the adult population (>16 years) in Barcelona (2004-2005). This study gathered information on active and passive smoking by means of a questionnaire and a saliva sample for cotinine determination. We analyzed sensitivity and specificity according to sex, age, smoking status (daily and occasional), and exposure to second-hand smoke at home. ROC curves and the area under the curve were calculated. RESULTS: The prevalence of smokers (daily and occasional) was 27.8% (95% CI: 25.2-30.4%). The optimal cut-point to discriminate smoking status was 9.2 ng/ml (sensitivity=88.7% and specificity=89.0%). The area under the ROC curve was 0.952. The optimal cut-point was 12.2 ng/ml in men and 7.6 ng/ml in women. The optimal cut-point was higher at ages with a greater prevalence of smoking. Daily smokers had a higher cut-point than occasional smokers. CONCLUSIONS: The optimal cut-point to discriminate smoking status in the adult population is 9.2 ng/ml, with sensitivities and specificities around 90%. The cut-point was higher in men and in younger people. The cut-point increases with higher prevalence of daily smokers.
OBJECTIVE: To assess the optimal cut-point for salivary cotinine concentration to identify smoking status in the adult population of Barcelona. METHODS: We performed a cross-sectional study of a representative sample (n=1,117) of the adult population (>16 years) in Barcelona (2004-2005). This study gathered information on active and passive smoking by means of a questionnaire and a saliva sample for cotinine determination. We analyzed sensitivity and specificity according to sex, age, smoking status (daily and occasional), and exposure to second-hand smoke at home. ROC curves and the area under the curve were calculated. RESULTS: The prevalence of smokers (daily and occasional) was 27.8% (95% CI: 25.2-30.4%). The optimal cut-point to discriminate smoking status was 9.2 ng/ml (sensitivity=88.7% and specificity=89.0%). The area under the ROC curve was 0.952. The optimal cut-point was 12.2 ng/ml in men and 7.6 ng/ml in women. The optimal cut-point was higher at ages with a greater prevalence of smoking. Daily smokers had a higher cut-point than occasional smokers. CONCLUSIONS: The optimal cut-point to discriminate smoking status in the adult population is 9.2 ng/ml, with sensitivities and specificities around 90%. The cut-point was higher in men and in younger people. The cut-point increases with higher prevalence of daily smokers.