title: An iterative technique for identifying smoking deceivers with application to the Scottish Heart Health Study.
abstract: BACKGROUND
  The study population consists of 3,977 self-declared nonsmokers for whom complete data on smoking biochemistry were available. Data were obtained from the Scottish Heart Health Study, a random cross-sectional population sample of 40- to 59-year-old men and women.
  
  
  METHODS
  Three biochemical markers of smoking (expired-air carbon monoxide, serum thiocyanate, and serum cotinine) are used together to derive optimum cut-points for distinguishing true nonsmokers from self-declared nonsmokers who are smoking deceivers, using an iterative procedure via a computer program.
  
  
  RESULTS
  The cut-points derived are, for carbon monoxide, 6 ppm (sensitivity, 0.81, and specificity, 0.94, when compared with the other two biochemical markers combined), for thiocyanate, 63.4 mumol/liter (sensitivity, 0.75; specificity, 0.92), and, for cotinine, 17.5 ng/ml (sensitivity, 0.77; specificity, 0.98). These cut-points are generally lower than those reported previously, primarily because other studies have taken self-reported smoking status to be the truth. The presence of deceivers among declared nonsmokers would tend to raise the biochemical levels of this group and hence of the cut-points.
  
  
  CONCLUSIONS
  The prevalence of smoking deception in the Scottish population is low: the frequency of those at or above all three cut-points is 1.2%, at or above two or more (the preferred definition of a smoking deceiver) is 2.2%, and at or above at least one is 16.4%.
authors.affiliation: Cardiovascular Epidemiology Unit, Ninewells Hospital, Dundee, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Woodward
authors.forename: H
authors.initials: H
authors.lastname: Tunstall-Pedoe
mesh_terms: D000328:Adult; D001944:Breath Tests; D002248:Carbon Monoxide / Q000032:analysis*; D003367:Cotinine / Q000097:blood*; D003430:Cross-Sectional Studies; D008192:Deception; D006801:Humans; D008875:Middle Aged; D015233:Models, Statistical; D015995:Prevalence; D012606:Scotland / Q000453:epidemiology; D012680:Sensitivity and Specificity; D012907:Smoking / Q000097:blood / Q000453:epidemiology* / Q000523:psychology; D013861:Thiocyanates / Q000097:blood*
chemical_list: D013861:Thiocyanates; D002248:Carbon Monoxide; D003367:Cotinine; C031760:thiocyanate