title: The effect of seeking consent on the representativeness of patient cohorts: iron-deficiency anaemia and colorectal cancer.
abstract: OBJECTIVE
  The study aimed to establish the level of selection bias that may occur should individual patient consent be sought, by comparing characteristics of consenters and nonconsenters to a request for access to medical records within a cohort of patients diagnosed with iron-deficiency anaemia (IDA).
  
  
  METHODS
  A cohort study and cross-sectional survey was carried out of consent preferences that compared the sociodemographic characteristics of patients providing or not providing consent for access to their records, the consent rates by participant subgroup and the predictors of consent/nonconsent.
  
  
  RESULTS
  Of 599 patients mailed requesting consent for access to their medical records, 425 (71.0%) responses were received. Of the valid responses, explicit consent was granted by 371 (62.7%) respondents, with 47 (7.9%) refusals. The characteristics of consenters and nonconsenters differed with regard to age, gender and deprivation quartile. Nonconsent was associated with younger age (40-60 years vs 60 + years; bivariate OR = 2.84; 95% CI = 2.01-4.02), female gender (OR = 1.62; 95% CI = 1.13-2.34) and being socioeconomically deprived (OR = 1.61; 95% CI = 1.15-2.26).
  
  
  CONCLUSIONS
  The current research governance framework demonstrates a conflict between protecting the rights of the individual and the development of a sound research base to improve the delivery of healthcare services for society as a whole. If epidemiological research includes data only from individuals who have given consent for access to their records, the resulting selection bias may have consequences for the scientific validity and generalizability of research findings, and ultimately the quality of patient care.
authors.affiliation: Primary Care Clinical Sciences, School of Health and Population Sciences, University of Birmingham, Edgbaston, West Midlands B15 2TT, UK.
authors.forename: S
authors.initials: S
authors.lastname: Damery
authors.forename: R
authors.initials: R
authors.lastname: Ryan
authors.forename: R J
authors.initials: RJ
authors.lastname: McManus
authors.forename: S
authors.initials: S
authors.lastname: Warmington
authors.forename: H
authors.initials: H
authors.lastname: Draper
authors.forename: S
authors.initials: S
authors.lastname: Wilson
mesh_terms: D022126:Access to Information; D000328:Adult; D000367:Age Factors; D018798:Anemia, Iron-Deficiency / Q000150:complications / Q000453:epidemiology*; D015179:Colorectal Neoplasms / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology*; D003430:Cross-Sectional Studies; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D007258:Informed Consent; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D018579:Patient Selection; D045808:Refusal to Participate; D015983:Selection Bias; D012737:Sex Factors; D012959:Socioeconomic Factors