title: Biochemical verification of the self-reported smoking status of screened male smokers of the Dutch-Belgian randomized controlled lung cancer screening trial.
abstract: BACKGROUND
  Smoking is the main cause of lung cancer, so data linked to smoking behaviour are important in lung cancer screening trials. However, self-reporting data concerning smoking behaviour are mainly used. The aim of this study was to biochemically determine the validity and reliability of self-reported smoking status among smokers at high risk for developing lung cancer participating in the Dutch-Belgian lung cancer screening (NELSON) trial.
  
  
  METHODS
  For this sub study, a random sample of 475 men was selected who were scheduled for the fourth screening round in the NELSON trial. They were asked to complete a short questionnaire to verify the smoking behaviour for the previous seven days and a blood sample was collected to measure the cotinine level. The validity (sensitivity (Se), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV)) and reliability (Kappa) of the self-reported smoking status compared to the cotinine level (as golden standard) were determined.
  
  
  RESULTS
  Both a completed questionnaire as well as a cotinine level were available for 199 (41.9%) participants. Based on these data, Se and Sp were respectively 98% (95%-Confidence Interval (CI): 91-99) and 98% (95%-CI: 93-100). PPV and NPV were 98% and 96% and Kappa was 0.96.
  
  
  CONCLUSIONS
  In conclusion, the validity of the self-reported smoking status turned out to be reliable amongst men at high risk for developing lung cancer who participate in the NELSON lung cancer screening trial.
authors.affiliation: Department of Public Health, Erasmus MC Rotterdam, Dr. Molewaterplein 40, 3015 GD Rotterdam, The Netherlands. Electronic address: c.vanderaalst@erasmusmc.nl.
authors.forename: Carlijn M
authors.initials: CM
authors.lastname: van der Aalst
authors.affiliation: Department of Public Health, Erasmus MC Rotterdam, Dr. Molewaterplein 40, 3015 GD Rotterdam, The Netherlands.
authors.forename: Harry J
authors.initials: HJ
authors.lastname: de Koning
mesh_terms: D000368:Aged; D001530:Belgium / Q000453:epidemiology; D006801:Humans; D008175:Lung Neoplasms / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology*; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D011159:Population Surveillance; D057566:Self Report; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects*
keywords: Biochemical validation; Lung cancer; Screening; Self-report; Smoking