title: The impact of consent on observational research: a comparison of outcomes from consenters and non consenters to an observational study.
abstract: BACKGROUND
  Public health benefits from research often rely on the use of data from personal medical records. When neither patient consent nor anonymisation is possible, the case for accessing such records for research purposes depends on an assessment of the probabilities of public benefit and individual harm.
  
  
  METHODS
  In the late 1990s, we carried out an observational study which compared the care given to affluent and deprived women with breast cancer. Patient consent was not required at that time for review of medical records, but was obtained later in the process prior to participation in the questionnaire study. We have re-analysed our original results to compare the whole sample with those who later provided consent.
  
  
  RESULTS
  Two important findings emerged from the re-analysis of our data which if presented initially would have resulted in insufficient and inaccurate reporting. Firstly, the reduced dataset contains no information about women presenting with locally advanced or metastatic cancer and we would have been unable to demonstrate one of our initial key findings: namely a larger number of such women in the deprived group. Secondly, our re-analysis of the consented women shows that significantly more women from deprived areas (51 v 31%, p = 0.018) received radiotherapy compared to women from more affluent areas. Previously published data from the entire sample demonstrated no difference in radiotherapy treatment between the affluent and deprived groups.
  
  
  CONCLUSIONS
  The risk benefit assessment made regarding the use of medical records without consent should include the benefits of obtaining research evidence based on 100% of the population and the possibility of inappropriate or insufficient findings if research is confined to consented populations.
authors.affiliation: General Practice and Primary Care, Division of Community Based Sciences, Faculty of Medicine, University of Glasgow, 1 Horselethill Road, Glasgow, G12 9LX, UK. u.macleod@clinmed.gla.ac.uk
authors.forename: Una
authors.initials: U
authors.lastname: Macleod
authors.forename: Graham C M
authors.initials: GC
authors.lastname: Watt
mesh_terms: D001943:Breast Neoplasms / Q000473:pathology / Q000628:therapy*; D005260:Female; D006801:Humans; D007258:Informed Consent; D008499:Medical Records; D009367:Neoplasm Staging; D019370:Observation / Q000379:methods*; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires