title: Participation rates in the selection of population controls in a case-control study of colorectal cancer using two recruitment methods.
abstract: OBJECTIVE
  Low participation rates in the selection of population controls are an increasing concern for the validity of case-control studies worldwide.
  
  
  METHODS
  We conducted a pilot study to assess two approaches to recruiting population controls in a study of colorectal cancer, including a face-to-face interview and blood sample collection. In the first approach, persons identified through a population roster were invited to participate through a telephone call by an interviewer telephoning on behalf of our research center. In the second approach, individuals were identified from the lists of selected family practitioners and were telephoned on behalf of the family practitioner.
  
  
  RESULTS
  When the second method was used, participation rates increased from 42% to 57% and the percentage of refusals decreased from 47% to 13%. The reasons for refusing to participate did not differ significantly between the two methods.
  
  
  CONCLUSIONS
  Contact through the family practitioner yielded higher response rates in population controls in the study area.
authors.affiliation: Center for Research in Environmental Epidemiology, Barcelona, Spain. gcastano@creal.cat
authors.forename: Gemma
authors.initials: G
authors.lastname: Castaño-Vinyals
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Nieuwenhuijsen
authors.forename: Víctor
authors.initials: V
authors.lastname: Moreno
authors.forename: Estela
authors.initials: E
authors.lastname: Carrasco
authors.forename: Elisabet
authors.initials: E
authors.lastname: Guinó
authors.forename: Manolis
authors.initials: M
authors.lastname: Kogevinas
authors.forename: Cristina M
authors.initials: CM
authors.lastname: Villanueva
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D016022:Case-Control Studies; D002391:Catchment Area, Health; D015179:Colorectal Neoplasms / Q000453:epidemiology*; D035061:Control Groups; D005194:Family Practice; D006304:Health Status; D006801:Humans; D007407:Interviews as Topic; D008875:Middle Aged; D009042:Motivation; D010560:Personnel Selection / Q000379:methods*; D010865:Pilot Projects; D045808:Refusal to Participate / Q000523:psychology / Q000706:statistics & numerical data*; D012042:Registries; D013030:Spain / Q000453:epidemiology; D013997:Time Factors; D014195:Travel; D055815:Young Adult