• We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
Logo of heartHeartVisit this articleSubmit a manuscriptReceive email alertsContact usBMJ
Heart. Sep 2007; 93(9): 1024–1025.
PMCID: PMC1955004

Consent bias in research: how to avoid it

Abstract

See article on page 1116

Keywords: selection bias, consent, observational research

Consent bias, also known as authorisation bias or volunteer bias, is described as a systematic error in creating patient groups, such that they differ with respect to study outcome. That is, the groups differ in measured or unmeasured baseline characteristics because of the way participants were selected or assigned. It is also used to mean that the participants are not representative of all possible participants.1 In short, it describes the impact on a study when those who consent to participate in research differ from those who do not or cannot consent. Buckley et al2 in the current edition of Heart (see article on page 1116) add to the small but important body of evidence showing how ethical requirements can bias medical research in the area of cardiovascular disease in a large community‐based cohort.3,4

Why is consent bias important?

Why is consent bias important for researchers and clinicians? In a review Hewison and Haines noted that consent requirements for recruiting patients to medical research could result in a failure to include participants who were most likely to benefit from interventions, such as older or socioecononomically deprived patients.5 It might lead to under‐ or overestimation of incidence or prevalence of a condition, it might bias assessment of an association between risk factors and health outcome, fail to detect differences in quality of care between certain patient groups and fail to capture the full range of views about a health concern. Biased research ultimately leads to poorer patient care, as evidence may be unreliable or invalid (low response rate), misleading (failure to capture an important association owing to selection bias) or lacking (failure to start or complete research projects owing to prohibitive costs and administrative burden).

Although scientific evidence on the effects of consent requirements is growing, there has been surprisingly little research into patients' views on this issue. Ethical review boards often enforce the opt‐in approach with the patients' interest at heart. Whereas there is a suggestion that an opt‐in approach is what patients prefer6 or expect,7 there is no evidence that patients would chose improved confidentiality over improved health, if asked to make a cost–benefit trade‐off between poor medical research and the risk of intrusion of privacy. Non‐response is more likely to be due to apathy8 or misconception9 than to principled objection. Few patients deny consent,8 or object,10 when contacted directly, and even fewer complain about being approached for research.8

What can researchers do about consent bias?

One way to deal with consent bias, in an environment where opt‐out is no longer considered an ethical option, is to adjust for it using an anonymised sample of the full patient data.11 However, this is no panacea. Although the proposed method may detect bias and adjust for it, it is also clear that no amount of statistical manipulation can remedy poor data. In addition, even obtaining anonymised data represents hurdles and the process is likely to add to the recognised substantial time‐intensive and costly burden of ethics and governance requirements.12

An alternative solution for UK researchers would be an application to the Patient Information Advisory Group (PIAG) provision under the Health and Social Care Act (2001). This body can give permission to use data without patient consent, where the effort to obtain consent is impractical and it can be proved that a low response rate would compromise the validity of the research. Application to the PIAG, however, is still a lengthy process and what constitutes compromised research or a disproportionate effort to obtain consent is open to interpretation.

Another plausible solution would be explicitly to ask the ethics review board to consider the opt‐out approach as default when submitting an ethics application and draw on published research as evidence in favour of the opt‐out approach.3 The patients' right to opt out of their data being used is safeguarded and patients who would not be able to opt out owing to mental ill health or terminal illness would be protected by their doctors from being approached for research.5

What can ethics review bodies do about consent bias?

It is the interpretation of the law by guardians and review bodies rather than the law (Common Law of Confidentiality, the Data Protection Act 1998 and the Human rights Act 1998) itself which unnecessarily hinders important medical research, as some ethics committees find opting‐out of patient recruitment acceptable.13 In the light of observed variability in decision making, a recent report issued by the Academy of Medical Sciences called for a clearer framework on these issues.14 In addition to considering opt‐out as the default, an explicit assessment of risks and benefits has been proposed, which might help sensible, more standardised decisions for each individual study to be reached.15

What can clinicians do about consent bias?

It is important that clinicians and patients as “end users” of research can spot consent bias and draw appropriate conclusions. In addition to critically appraising each paper, we propose a checklist to look for effects of consent or authorisation bias (box 1).

Box 1: Checklist to look for effects of consent bias

  • Are the total numbers in the study approached for consent reported? If not, it is difficult to gauge how representative this paper is of your patient population—treat with caution.
  • Is the consent method documented?
    • Is it opt‐in or active consent (more likely to lead to bias)
    • or opt‐out or passive consent (less likely to lead to bias).
  • Is the percentage response/consent rate reported? A response rate of at least 60% is common in community cohorts, whereas it is expected to be higher for hospital‐based cohorts. A low response rate may lead to diminished validity for your patient population.
  • If the study used an opt‐in approach:
    • Have comparisons or adjustments been made to ensure generalisability?
    • Do the authors report the impact of their approach on generalisability or validity on their study?
  • Are the baseline characteristics of the patients in the study broadly similar to your patient population?

Conclusion

Consent bias has potentially serious consequences for the quality of medical research, the use of public resources and the quality of patient care. A public debate on the benefits and harms of being approached for medical research is important but has not yet happened. As Buckley et al argue in their paper, there is a public lack of knowledge about research, and education about research was shown to increase patients' willingness to participate in research.16 Possibly, the public may decide that individual privacy is more important than the societal benefits of research, once an open debate has taken place. In this case, patient education may be the only way forward to ensure adequate and unbiased participation in research. Until that debate, however, we need more fearless ethics committees, more critical doctors, more assertive researchers and rigorous data security.

Footnotes

Conflict of interest: None.

References

1. Bandolier Selection bias. 2007. Available at http://www.jr2.ox.ac.uk/bandolier/booth/glossary/selectbi.html (accessed 1 June 2007)
2. Buckley B, Murphy A W, Byrne M. et al Selection bias resulting from the requirement for prior consent in observational research: a community cohort of people with ischaemic heart disease. Heart 2007. 931116–1120.1120 [PMC free article] [PubMed]
3. Junghans C, Feder G, Hemingway H. et al Recruiting patients to medical research: double blind randomised trial of “opt‐in” versus “opt‐out” strategies. BMJ 2005. 331940 [PMC free article] [PubMed]
4. Al‐Shahi R, Vousden C, Warlow C, for the Scottish Intracranial Vascular Malformation Study (SIVMS) Steering Committee Bias from requiring explicit consent from all participants in observational research: prospective, population based study. BMJ 2005. 331942 [PMC free article] [PubMed]
5. Hewison J, Haines A. Overcoming barriers to recruitment in health research. BMJ 2006. 333300–302.302 [PMC free article] [PubMed]
6. Robling M R, Hood K, Houston H. et al Public attitudes towards the use of primary care patient record data in medical research without consent: a qualitative study. J Med Ethics 2004. 30104–109.109 [PMC free article] [PubMed]
7. Wilkie T. Public opinion may force researchers to seek “opt in” consent for all studies (commentary). BMJ 2001. 3221221
8. Iversen A, Liddell K, Fear N. et al Consent, confidentiality, and the Data Protection Act. BMJ 2006. 332165–169.169 [PMC free article] [PubMed]
9. Crombie I K, McMurdo M E T. et al Overcoming barriers to recruitment in health research: Concerns of potential participants need to be dealt with. BMJ 2006. 333398 [PMC free article] [PubMed]
10. Barrett G, Cassell J A, Peacock J L. et al National survey of British public's views on use of identifiable medical data by the National Cancer Registry. BMJ 2006. 3321068–1072.1072 [PMC free article] [PubMed]
11. Boardman H F, Thomas E, Ogden H. et al A method to determine if consenters to population surveys are representative of the target study population. J Public Health 2005. 27212–214.214 [PubMed]
12. Elwyn G, Seagrove A, Thorne K. et al Ethics and research governance in a multicentre study: add 150 days to your study protocol. BMJ 2005. 330847 [PMC free article] [PubMed]
13. Pegg M S. Overcoming barriers to recruitment in health research: Some research ethics committees believe in facilitating ethical research. BMJ 2006. 333398 [PMC free article] [PubMed]
14. Academy of Medical Sciences Personal data for public good: using health information in medical research. London: The Academy of Medical Sciences, 2006, Available at http://www.acmedsci.ac.uk (accessed 3 June 2007)
15. Davies C, Collins R. Balancing potential risks and benefits of using confidential data. BMJ 2006. 333349–351.351 [PMC free article] [PubMed]
16. Cousins G, McGee H, Ring L. et alPublic perceptions of biomedical research: a survey of the general population in Ireland. Dublin: Health Research Board, 2005

Articles from Heart are provided here courtesy of BMJ Group
PubReader format: click here to try

Formats:

Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...

Links

  • PubMed
    PubMed
    PubMed citations for these articles

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...