Elsevier

Social Science & Medicine

Volume 47, Issue 11, December 1998, Pages 1825-1840
Social Science & Medicine

Informed consent for clinical trials: in search of the “best” method

https://doi.org/10.1016/S0277-9536(98)00235-4Get rights and content

Abstract

Objective: To review the literature on comparisons between different methods of obtaining informed consent for clinical trials. Design: Eight hundred and twelve articles were traced, in the process of conducting a systematic review of the ethics of clinical trials, by searching a number of sources: bibliographic databases (Medline, Psychlit and BIDS science and social science indices), hand searches, personal contacts, an original collection and a systematic follow-up of reference lists. Fourteen research reports were found which provided comparative data on different methods of obtaining informed consent. Eleven of these used a randomised design. Studies were classified according to three outcome measures (anxiety, consent rate and understanding). Results: The results of the various studies suggest that giving people more information and more time to reflect tends to be associated with a lower consent rate. There seems to be an optimal level of information about side-effects such that patients are not overburdened by detail, while grasping the most important risks. More information in general is associated with greater awareness of the research nature of the trial, voluntariness of participation, right to withdraw and (available) alternative treatments. This result does not, however, extend to explanations of the concept of randomisation on which the literature is contradictory — sometimes more information is associated with increased understanding of the concept and sometimes it is not. Although divulging less information seems to be associated with less anxiety, there is evidence of an interaction with knowledge — high levels of knowledge are significantly associated with less anxiety, irrespective of consent method. The more that patients know before they are invited to participate in a trial, the better equipped they are to cope with the informed consent procedure. Conclusion: There is some evidence to suggest that there is an optimal amount of information which enhances patient understanding and which might, in turn, reduce anxiety. However, the studies were not altogether conclusive. More work needs to be carried out, especially on public understanding of science and on how different ways of explaining scientific concepts affect that understanding.

Introduction

“Informed consent” is perhaps the most controversial issue in the ethics of medical research today. Although biomedical research has a history dating back to Aristotle, the idea of informed consent only surfaced in the early part of the nineteenth century and finally supplanted the paternalistic view set out in the Hippocratic Oath. Informed consent is based on the notion that a person of competent mind has the right to determine what is done to him/her and the right to determine what is not done. The request for informed consent thus serves to respect a patient's autonomy. Gross violations of this principle led to its explicit formulation in the Nuremberg Code (1949) and, more expansively, in the Declaration of Helsinki (1964). These guidelines both stress that informed consent should be voluntary, not only technically but also in spirit, and that adequate disclosure of information is crucial. Adequate information typically consists of (1) details about the procedures in question, (2) purpose of the research, (3) (expected) benefits of treatment, (4) (expected) side-effects, (5) (available) alternatives and (6) right to withdraw. Clinical trials have become one of the most widespread methods of clinical research, making them the cornerstone of evidence-based practice. The method by which potential participants are informed of their options is therefore a matter of considerable personal and public interest. We have conducted a systematic review of the empirical literature which has examined the effect of different methods of obtaining “informed consent” on recruitment rates, knowledge, attitudes and anxiety.

Section snippets

Materials and methods

We first carried out a systematic search of all literature relating to the ethics of clinical trials. We used five different methods to ascertain the relevant articles namely, an electronic literature survey (conducted on the three databases, Medline, Psychlit and BIDS1 science and social science citation indices), hand searches, personal

Studies under review

There were fourteen studies providing data on different methods of obtaining informed consent, of which all except three (McLean, 1980; Dal-Re, 1991; Levene et al., 1996) used randomised controlled trial designs i.e. they were trials of methods to get consent for trials. In terms of outcome, eleven studies examined recruitment rates to the clinical trial in question, eight studies examined understanding, and five studies looked at psychological well-being (four studies examined all three

Methodological issues

Results from hypothetical scenarios may not easily be extrapolated to the “real life” situation (King, 1986). Indeed, patients faced with difficult decisions, in reality, may be more concerned to ensure that they understand the issues, or they may make different trade-offs. Data accrued from studies based on real trials are thus more useful.

Several different instruments were used to measure psychological well-being and one administered a formal psychometric scale, while the others relied on

Conclusion

The moral imperative of informed consent is an ideal whereby patients should be given full details of the trial procedure so that a person can determine what is or is not done to him/her. In theory, if autonomy is the foundation of informed consent, a patient should be asked whether or not they wish any information upon which to base a decision, and then, given an expressed desire for information, the patient should make a considered decision about trial entry. Practice, as ever, falls short of

Acknowledgements

This study was supported by the methodology section of the National Health Technology Assessment programme. We would like to thank Mr Martin Gill, Dr Chris Hyde and Ms Jennifer Jackson for their helpful comments.

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