Informed consent forms the cornerstone of ethical requirements in healthcare research [1, 2]. In the context of healthcare research, the giving of informed consent signifies that an individual has made an informed and voluntary decision about their participation in a research study. Randomised controlled trials (RCTs) usually require all participants to sign an informed consent document indicating that they have understood the information they have been provided with before they commence participation in the trial .
To assist in making an informed decision about participation, potential trial participants in the UK are provided with a patient information leaflet (PIL) that contains information about the RCT. The information included in PILs is guided by the Declaration of Helsinki, the International Conference on Harmonisation Good Clinical Practice (ICH GCP) and also by national guidance such as the National Research Ethics Service (NRES) [1, 3, 4]. As defined by the guidance, the PIL should include, at minimum, information about: the purpose of the trial; procedures; interventions; possible risks and benefits; sources of finance; potential conflicts of interest; and the researcher’s affiliation [1, 3]. The guidance for informational requirements covers predominantly fact-based information and is standardised at a population level [1, 3].
Currently the PIL and consent form are the only components of the consent decision making process for RCTs that are formally regulated, through specific guidance, and reviewed by ethics committees or internal review bodies . However, as with decisions about treatment, potential participants vary in the amount of information they desire when faced with a decision about trial participation [5–7]. As such, within a trial context where the information minimum has been pre-determined by the guidance [1, 3, 4], many potential participants’ preferences for information may be exceeded  and other approaches to supporting decision making may be required. Despite this, there is evidence that some trial participants, both those considering participation and those actively enrolled in clinical trials, fail to understand key components of the trial processes or rationale [8–10]. This has ranged from misunderstandings about: risks ; the right to withdraw ; confidentiality ; side effects ; and purpose of the trial . This suggests that in the context of trial participation, existing approaches to information provision may be sub-optimal and some decisions may not have been based on a full understanding or consideration of all the relevant issues. This may be because the information is too complex or not designed to support an informed decision but rather to present factual information to the potential participant. A range of studies have explored ways of improving information, and have tended to focus on the content and structure of the information . For example: the length of the information sheet, that is, short versus long leaflets [10, 15]; simplified or enhanced versions of the same PIL [16, 17]; patient-specific information versus generic information [18, 19]; linguistic analysis of leaflets ; consumer involvement in development of PILs ; audio-visual information ; computer-based information ; and user testing to improve content .
As discussed above, the literature to date has tended to focus on the provision of information, to improve understanding about trial processes, with the aim of making the consent process more 'informed’. However, informed decision making in the context of trial participation is a complex process and requires more than just greater understanding or comprehension of certain fact-based information. For example, key considerations which are regarded by established theories of decision making as being important for making 'good’ decisions (for example considering the alternatives (for example standard care and what that is), making trade-offs and evaluating potential outcomes of the decision ) might not be presented or discussed at all during the informed consent discussion or explicit in the PIL. These omissions may stem from the conventional conceptualisation of trial participation as an act of 'informed consent’. This conceptualisation likely relates to the ethical and regulatory requirements, rather than viewing deliberations and decisions about participation as broader and more complex .
Decision aids have been developed for a variety of treatment and screening decisions as a means of improving 'informed decisions’ in particular contexts and across the decision making process . These decision aids provide information about: the available options and any associated outcomes; personalise information by including exercises to help patients think about what matters most to them; and provide ways of communicating this with the healthcare professional to reach a decision . There is substantial evidence to suggest that decision aids can positively influence outcomes, such as: improving knowledge, especially when there is clinical equipoise; providing accurate perceptions of outcome probabilities; and align preferred outcomes with the choice made .
As discussed previously, the traditional conceptualisation of informed consent in RCTs is as a behaviour relating to understanding rather than promoting informed decisions. This may have led to the information contained within PILs being focussed on fact-based trial information rather than, for example, what trial participation might mean for that individual. Yet, these personal considerations do play a significant role for people when deciding whether or not to participate in a trial  and this is often the type of information contained within treatment decision aids. As such, it is perhaps timely to re-think the way in which decisions about trial participation and discussions about informed consent are supported.
Preliminary studies exploring the potential of decision aids for use in the informed consent process for RCTs have shown promise in that they appear to improve aspects of the decision making process [28–32]. Decision aids to support decisions about trial participation have been shown to be acceptable and valued by potential participants [28, 29]. In these studies, the decision aid was a substitute for the existing PIL and contained all of the required information expected to be in a PIL in addition to those expected to be in a decision aid. Specifically, decision aids in this context have been shown to improve understanding about the trial and its associated interventions [28, 29], produce low levels of decision conflict  and not raise anxiety [28, 29]. However, these studies had small sample sizes and were set within a hypothetical trial context. As such, the need for further research has been noted [28–32]. A recent study examined the extent to which existing informed consent documents conform to standards for encouraging good quality decision making as laid out by International Patient Decision Aid Standards (IPDAS) [33, 34]. The evaluation tool used in the study by Brehaut and colleagues contained two sections: a series of items derived from the IPDAS and a set of items derived from published guidance on informed consent . Only the first section of the tool, including items developed from the IPDAS, was used and the majority of the included PILs were developed in the US with approximately half being for cancer trials . Guidance for US PILs differs from that for UK PILs with regard to whether specific information is presented in either the information sheet or consent form, with UK consent forms being a one-page document, whereas US consent forms are longer and contain much of the information contained within the UK PIL. Moreover, the study by Brehaut and colleagues did not assess word count or readability, both of which can contribute to understanding of information and length of document.
Previous research has suggested that decision aids for trial participation have the potential to promote good quality decision making [28, 29] and specific components of decision aids that have been applied in RCTs have also offered promise [30, 35]. Therefore, this study aimed to assess the feasibility of assessing the extent to which items considered important in decision aids are present in existing UK PILs. We used the complete evaluation tool (developed by Brehaut et al.), alongside word count and readability 'calculators’, to evaluate PILs across a range of clinical conditions in a UK context.