title: [Reliability of covariates in baseline survey of a cohort study: Epidemiological Investigation on Cancer Risk Among Residents Who Reside Near The Nuclear Power Plants in Korea].
abstract: OBJECTIVE
  We evaluated the reliability of the possible covariates of the baseline survey data collected for the Epidemiological Investigation on Cancer Risk Among Residents Who Reside Near the Nuclear Power Plants in Korea.
  
  
  METHODS
  Follow-up surveys were conducted for 477 participants of the cohort at less than 1 year after the initial survey. The mean interval between the initial and follow-up surveys was 282.5 days. Possible covariates were identified by analyzing the correlations with the exposure variable and associations with the outcome variables for all the variables. Logistic regression analysis with stepwise selection was further conducted among the possible covariates to select variables that have covariance with other variables. We considered that these variables can be representing other variables. Seven variables for the males and 3 variables for the females, which had covariance with other possible covariates, were selected as representative variables. The Kappa index of each variable was calculated.
  
  
  RESULTS
  For the males, the Kappa indexes were as follow; family history of cancer was 0.64, family history of liver diseases in parents and siblings was 0.56, family history of hypertension in parents and siblings was 0.51, family history of liver diseases was 0.50, family history of hypertension was 0.44, a history of chronic liver diseases was 0.53 and history of pulmonary tuberculosis was 0.36. For females, the Kappa indexes were as follow; family history of cancer was 0.58, family history of hypertension in parents and siblings was 0.56 and family history of hypertension was 0.47.
  
  
  CONCLUSIONS
  Most of the possible covariates showed good to moderate agreement.
authors.affiliation: Department of Preventive Medicine, College of Medicine, Seoul National University, Korea.
authors.forename: Sanghyuk
authors.initials: S
authors.lastname: Bae
authors.forename: Bo-Young
authors.initials: BY
authors.lastname: Park
authors.forename: Zhong Min
authors.initials: ZM
authors.lastname: Li
authors.forename: Yoon-Ok
authors.initials: YO
authors.lastname: Ahn
mesh_terms: D000368:Aged; D015331:Cohort Studies; D015986:Confounding Factors, Epidemiologic; D004781:Environmental Exposure / Q000009:adverse effects; D005260:Female; D015438:Health Behavior; D006306:Health Surveys; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000453:epidemiology* / Q000209:etiology; D055848:Nuclear Power Plants; D056910:Republic of Korea / Q000453:epidemiology; D012737:Sex Factors