title: Assessment of alcohol consumption by mailed questionnaire in epidemiological studies: evaluation of misclassification using a dietary history interview and biochemical markers.
abstract: BACKGROUND
  Self-reported information on alcohol from questionnaires is generally assumed to introduce misclassification of consumption, mainly in the direction of underestimation. The aim of this study was to evaluate self-reported information on alcohol consumption from a mailed questionnaire by comparing to a dietary history interview and biochemical markers of alcohol intake.
  
  
  METHODS
  For 76 male twin pairs of the Finnish Twin Cohort Study aged 40-70 years information on self-reported alcohol consumption was collected through mailed questionnaire and dietary history interview. Carbohydrate-deficient transferrin (CDT), Gamma-glutamyltransferase (Gamma-GT) and mean corpuscular volume (MCV) were determined from blood samples.
  
  
  RESULTS
  Mean levels of CDT, gamma-GT and MCV showed a rise with increased self-reported alcohol consumption already at low levels of reported consumption (<20 g alcohol/day). There was a positive correlation between reported amount alcohol intake per day and levels of CDT (r = 0.46), gamma-GT (r = 0.32) and MCV (r = 0.36) but within the high consumption group (> or = 30 g/day) there was no such correlation. The questionnaire had sensitivity of 28-43% and specificity of 89% for identification of high consumers of alcohol using the biochemical markers as reference and sensitivity 41% and specificity 94% using the dietary history interview as reference. Sensitivity was improved when information on binge drinking (82%) or possible drinking problems (73%) was considered.
  
  
  CONCLUSIONS
  Comparison to dietary history interview as well as to biochemical markers indicate that self-reported information on alcohol consumption from a mailed questionnaire may be used to distinguish between groups with different levels of alcohol consumption. The suggested misclassification of high consumers implies that only strong associations between high alcohol intake and disease are likely to be detected in studies based on questionnaire data.
authors.affiliation: Division of Epidemiology, Stockholm Centre of Public Health, Stockholm, Sweden. sofia.carlsson@imm.ki.se
authors.forename: Sofia
authors.initials: S
authors.lastname: Carlsson
authors.forename: Niklas
authors.initials: N
authors.lastname: Hammar
authors.forename: Paula
authors.initials: P
authors.lastname: Hakala
authors.forename: Jaakko
authors.initials: J
authors.lastname: Kaprio
authors.forename: Jukka
authors.initials: J
authors.lastname: Marniemi
authors.forename: Tapani
authors.initials: T
authors.lastname: Rönnemaa
mesh_terms: D000328:Adult; D000368:Aged; D000428:Alcohol Drinking / Q000453:epidemiology*; D015415:Biomarkers; D004200:Diseases in Twins / Q000453:epidemiology; D005247:Feeding Behavior; D005387:Finland / Q000453:epidemiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012650:Self Disclosure; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires; D014168:Transferrin / Q000031:analogs & derivatives* / Q000378:metabolism; D005723:gamma-Glutamyltransferase / Q000097:blood
chemical_list: D015415:Biomarkers; D014168:Transferrin; C056759:carbohydrate-deficient transferrin; D005723:gamma-Glutamyltransferase