title: Validity of random-digit-dialing in recruiting controls in a case-control study.
abstract: OBJECTIVE
  To evaluate whether the participating controls represented the underlying population in a colorectal cancer case-control study in a geographically isolated North American population.
  
  
  METHODS
  The characteristics of the study controls recruited through Random-digit-dialing (RDD) were compared with those in the corresponding target population estimates.
  
  
  RESULTS
  Participating controls were more likely to have higher levels of education and income and were less likely to be smokers.
  
  
  CONCLUSIONS
  Study controls recruited through RDD tend to have higher socioeconomic status, which may lead to overestimation of a number of risk factors in this study.
authors.affiliation: Division of Community Health and Humanities, Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL, Canada. pwang@mun.ca
authors.forename: Peizhong Peter
authors.initials: PP
authors.lastname: Wang
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Dicks
authors.forename: Xianying
authors.initials: X
authors.lastname: Gong
authors.forename: Sharon
authors.initials: S
authors.lastname: Buehler
authors.forename: Jinhui
authors.initials: J
authors.lastname: Zhao
authors.forename: Josh
authors.initials: J
authors.lastname: Squires
authors.forename: Banfield
authors.initials: B
authors.lastname: Younghusband
authors.forename: John R
authors.initials: JR
authors.lastname: McLaughlin
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Parfrey
mesh_terms: D000328:Adult; D000368:Aged; D015982:Bias; D016022:Case-Control Studies; D004522:Educational Status; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009523:Newfoundland and Labrador; D018579:Patient Selection; D012307:Risk Factors; D012907:Smoking; D012923:Social Class; D013689:Telephone