[Optimal cut-point of salivary cotinine concentration to discriminate smoking status in the adult population in Barcelona].
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.
Martínez-Sánchez
Jose M
JM
Institut Català d'Oncologia-IDIBELL, L'Hospitalet de Llobregat, Barcelona, España. jmmartinez@ico.scs.es
Fu
Marcela
M
Ariza
Carles
C
López
María J
MJ
Saltó
Esteve
E
Pascual
José A
JA
Schiaffino
Anna
A
Borràs
Josep M
JM
Peris
Mercè
M
Agudo
Antonio
A
Nebot
Manel
M
Fernández
Esteve
E
D000293:Adolescent; D000328:Adult; D000368:Aged; D019540:Area Under Curve; D003367:Cotinine / Q000032:analysis*; D003430:Cross-Sectional Studies; D005260:Female; D006184:Habits; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012372:ROC Curve; D012463:Saliva / Q000737:chemistry*; D012680:Sensitivity and Specificity; D012907:Smoking / Q000453:epidemiology / Q000378:metabolism*; D013030:Spain / Q000453:epidemiology; D011795:Surveys and Questionnaires; D014028:Tobacco Smoke Pollution / Q000032:analysis* / Q000706:statistics & numerical data; D055815:Young Adult
D014028:Tobacco Smoke Pollution; D003367:Cotinine