title: Nonparticipation in a population-based trial to increase colorectal cancer screening.
abstract: BACKGROUND
  Many trials have tested different strategies to increase colorectal cancer (CRC) screening. Few describe whether participants are representative of the population from which they are recruited.
  
  
  OBJECTIVE
  To determine risk factors related to nonparticipation among patients enrolled in an integrated health plan and not up to date for CRC testing, in a trial to increase screening rates.
  
  
  METHODS
  Between July 2008 and October 2009, a total of 15,000 adults aged 50-74 years from 21 clinics in Washington State who were due for CRC screening were contacted. Nonparticipants were defined as English-speaking patients who did not engage in the call or refused participation while still potentially eligible. Log-binomial regression models were used to estimate the relative risk of nonparticipation. Analyses were completed between October 2010 and June 2011.
  
  
  RESULTS
  Patients who were nonwhite, had less education, used tobacco, had less continuity of care, and had lower rates of preventive care and cancer screening were more likely to be nonparticipants. Patients reporting never having received any type of CRC testing or screening were also more likely not to participate (62% of nonparticipants vs 46% of participants; adjusted RR=1.58, 95% CI=1.47, 1.70). Reasons for refusal included costs, risks of procedures, and not wanting their medical records reviewed.
  
  
  CONCLUSIONS
  Patients eligible for but not participating in the trial were more likely to be from minority socioeconomic and racial groups and had behaviors that can negatively affect cancer outcomes. Additional efforts are needed to recruit patients who need CRC screening the most.
  
  
  BACKGROUND
  This trial is registered at clinicaltrials.gov NCT 00697047.
authors.affiliation: Group Health Permanente, University of Washington Medical School, Seattle, USA. green.b@ghc.org
authors.forename: Beverly B
authors.initials: BB
authors.lastname: Green
authors.forename: Andy
authors.initials: A
authors.lastname: Bogart
authors.forename: Jessica
authors.initials: J
authors.lastname: Chubak
authors.forename: Sally W
authors.initials: SW
authors.lastname: Vernon
authors.forename: Leo S
authors.initials: LS
authors.lastname: Morales
authors.forename: Richard T
authors.initials: RT
authors.lastname: Meenan
authors.forename: Sharon S
authors.initials: SS
authors.lastname: Laing
authors.forename: Sharon
authors.initials: S
authors.lastname: Fuller
authors.forename: Cynthia
authors.initials: C
authors.lastname: Ko
authors.forename: Ching-Yun
authors.initials: CY
authors.lastname: Wang
mesh_terms: D000368:Aged; D015179:Colorectal Neoplasms / Q000175:diagnosis*; D019033:Delivery of Health Care, Integrated / Q000706:statistics & numerical data; D005260:Female; D015438:Health Behavior; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods* / Q000706:statistics & numerical data; D008875:Middle Aged; D010342:Patient Acceptance of Health Care / Q000706:statistics & numerical data*; D018579:Patient Selection; D044469:Racial Groups / Q000706:statistics & numerical data; D012044:Regression Analysis; D012959:Socioeconomic Factors; D016312:Treatment Refusal