Abstract: We included 16 studies involving data from 1884 participants. Nine studies included participants considering real clinical trials, and eight included participants considering hypothetical clinical trials, with one including both. All studies were conducted in high-income countries. There is still much uncertainty about the effect of audio-visual informed consent interventions on a range of patient outcomes. However, when considered across comparisons, we found low to very low quality evidence that such interventions may slightly improve knowledge or understanding of the parent trial, but may make little or no difference to rate of participation or willingness to participate. Audio-visual presentation of informed consent may improve participant satisfaction with the consent information provided. However its effect on satisfaction with other aspects of the process is not clear. There is insufficient evidence to draw conclusions about anxiety arising from audio-visual informed consent. We found conflicting, very low quality evidence about whether audio-visual interventions took more or less time to administer. No study measured researcher satisfaction with the informed consent process, nor ease of use. The evidence from real clinical trials was rated as low quality for most outcomes, and for hypothetical studies, very low. We note, however, that this was in large part due to poor study reporting, the hypothetical nature of some studies and low participant numbers, rather than inconsistent results between studies or confirmed poor trial quality. We do not believe that any studies were funded by organisations with a vested interest in the results. The value of audio-visual interventions as a tool for helping to enhance the informed consent process for people considering participating in clinical trials remains largely unclear, although trends are emerging with regard to improvements in knowledge and satisfaction. Many relevant outcomes have not been evaluated in randomised trials. Triallists should continue to explore innovative methods of providing information to potential trial participants during the informed consent process, mindful of the range of outcomes that the intervention should be designed to achieve, and balancing the resource implications of intervention development and delivery against the purported benefits of any intervention. More trials, adhering to CONSORT standards, and conducted in settings and populations underserved in this review, i.e. low- and middle-income countries and people with low literacy, would strengthen the results of this review and broaden its applicability. Assessing process measures, such as time taken to administer the intervention and researcher satisfaction, would inform the implementation of audio-visual consent materials.

Plain-language summary: We searched for studies of audio-visual informed consent interventions which allocated people to an experimental or control group by a random or quasi-random process, published up until June 2012. We found 16 studies, involving a total of 1884 people. Nine studies included people considering real clinical trials, eight included people asked to imagine participating in a clinical trial (a hypothetical trial), with one including both. Most of the studies were conducted in the United States. People were considering (or imagined considering) participation in a range of different clinical trials, including those testing cancer treatments and drugs for mental health problems. The audio-visual informed consent information was presented on computers, DVDs, videos and CD-ROMs. They included voice overs by professional actors, real patients talking about their experiences and a combination of words, pictures and audio to explain the technical concepts. In some studies, people also received the usual written informed consent forms and/or a face-to-face explanation by the study staff. There is low to very low quality evidence that audio-visual consent interventions may slightly improve knowledge or understanding of the parent trial, but may make little or no difference to rate of participation or willingness to participate. Audio-visual presentation may improve participation satisfaction with the information provided. However its effect on satisfaction with other aspects of the process is not clear. There is not enough evidence to draw conclusions about anxiety arising from audio-visual informed consent. There is conflicting, very low quality evidence about whether audio-visual interventions take more or less time to administer, and no study measured researcher satisfaction with the informed consent process, nor ease of use. We do not believe that any studies were funded by organisations with a vested interest in the results. The quality of evidence from real clinical trials was low, and from hypothetical clinical studies, very low. This is because of the small number of people in the studies, and some issues in the way they were conducted. If the next update of this review includes more studies of audio-visual informed consent presentation, it could change the results of this review.