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  3. Bias from requiring explicit consent from all participants in observational research: prospective, population based study
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Bias from requiring explicit consent from all participants in observational research: prospective, population based study

BMJ 2005; 331 doi: https://doi.org/10.1136/bmj.38624.397569.68 (Published 20 October 2005) Cite this as: BMJ 2005;331:942
  1. Rustam Al-Shahi (Rustam.Al-Shahi{at}ed.ac.uk), specialist registrar in neurology1,
  2. Céline Vousden, medical student1,
  3. Charles Warlow, professor of medical neurology for the Scottish Intracranial Vascular Malformation Study (SIVMS) Steering Committee1
  1. 1Bramwell Dott Building, Division of Clinical Neurosciences, University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU
  1. Correspondence to: Rustam Al-Shahi
  • Accepted 23 August 2005

Abstract

Objective To evaluate the differences between adults who consent to participate in observational research, and those who do not.

Design Prospective, population based cohort study.

Setting Primary and secondary care throughout Scotland.

Participants 187 adults (aged ≥16 years) resident in Scotland at the time of their first diagnosis of a brain arteriovenous malformation in 1999-2002.

Intervention Postal consent form sent via participants' general practitioner.

Main outcome measures Differences between consenters and non-consenters in demographic and clinical features at first presentation, and outcome during follow-up.

Results 111 adults (59%) consented to participate in the study. These consenters were not significantly different from non-consenters in age, sex, or socioeconomic status at first presentation. However, consenters were significantly more likely than non-consenters to present alive and independent, and with a seizure. During follow-up, consenters were significantly more likely to receive interventional treatment. Although consenters' survival was significantly better, they were more likely to have a seizure during follow-up. Presentation with intracranial haemorrhage conferred a higher risk of subsequent haemorrhage when the whole cohort was analysed, but not when it was restricted to consenters.

Conclusions We have found differences between adults who consent to participate in observational records-based research and those who do not, or cannot, consent. Blanket requirements for explicit consent for the use of individuals' identifiable data can bias disease registers, epidemiological studies, and health services research.

Footnotes

  • Contributors RA-S and CW conceived and planned the study. RA-S and CV conducted the study, using data collected by the study team, overseen by the study's steering committee. All authors contributed to the study design and analysis and interpretation of data. RA-S drafted the article, and all authors revised it critically for important intellectual content. All authors gave final approval of the version to be published. RA-S and CW are guarantors for the paper.

  • Funding The Scottish intracranial vascular malformation study was funded by the UK Medical Research Council, the Chief Scientist Office of the Scottish Executive Health Department, and the UK Stroke Association.

  • Competing interests None declared.

  • Ethical approval The Multicentre Research Ethics Committee for Scotland approved the study (MREC/98/0/48).

  • Accepted 23 August 2005
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