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What influences communication about retention in randomised trials: a multi-trial, theory-based analysis exploring trial staff perspectives



Retention (participants completing a trial) is a persistent, and often under-studied, challenge within clinical trials. Research on retention has focussed on understanding the actions of participants who decide to remain or withdraw from trial participation and developing interventions to target improvements. To better understand how trial staff may influence participants to remain or withdraw from trials, it is important to explore the experiences of staff that recruit and retain said participants and how the process of recruitment impacts retention.


Two qualitative interview studies informed by the Theoretical Domains Framework (TDF) were conducted with staff involved in various stages of clinical trials. The first set of interviews were focussed on staff perceptions about why participants failed to be retained and what helped to keep others engaged in trials, but also explored more generally what strategies or factors contributed to retention in trials. The second set of interviews were focussed on staff perceptions specifically about the recruitment and informed consent process and how that may influence trial retention. All interviews were analysed using the TDF and assigned to relevant behavioural domains according to perceived barriers/facilitators of the target behaviour. Belief statements were generated, summarising the narrative content of related responses within these behavioural domains. These belief statements were further analysed for themes that captured higher order relationships between separate beliefs within and between behavioural domains.


Twenty-five participants (9 retention staff and 16 recruitment staff) were interviewed. Themes describing the barriers/facilitators to retention broadly, and to communication of retention information at consent, were generated. Four themes on retention broadly and six themes on communication of retention information at consent were identified. Overall, beliefs within all fourteen TDF domains populated these themes.


This study explored staff perspectives on retention and how they interpret their behaviour as contributing to retention success. Perspectives varied considerably but several key themes regarding communication were seen consistently. Specific barriers and facilitators within these findings will serve to guide the design of a behavioural intervention aimed at addressing issues within retention. Findings contribute to a notable gap in the literature on staff behaviour in trials and on retention generally.

Peer Review reports


Randomized clinical trials (herein referred to as trials) are often considered the foundation of evidence-based medicine [1]. The conduct of trials requires the careful coordination of complex healthcare networks and research teams. However, even the most well-coordinated trials face logistical issues that affect trial outcomes. These can include coordinating teams across multiple sites, differences in site-specific training of staff, and the competing demands of other trials, to name a few. Two of the most persistent challenges when conducting trials are recruiting and retaining participants (i.e., identifying potential participants, enrolling them, and then keeping those enrolled on study until data collection is complete). Methodological research into trial recruitment and retention have been identified as top priorities for the UK clinical trials community [2, 3]. Recruitment has often been the focus of trials methods research, which leaves research into improving retention in need of investment [4,5,6].

Failures in trial retention can be defined as ‘instances where participants are prematurely “off-study” (i.e., consent is withdrawn or participants are lost to follow-up) and thus outcome data cannot be obtained from them’ [7]. It is estimated that around 50% of trials experience a loss to follow up of at least 11% with some as high as 20% [8]. In fact, some pose that any trial with loss to follow-up over 20% would fail to withstand scrutiny on the strength of their results [9, 10]. The generalizability and internal validity of a trial is at risk from differential loss to follow-up as it introduces bias that can skew effects towards one group or another [5, 10, 11]. Even non-differential loss to follow-up can result in a loss of statistical power and the associated confidence in conclusions drawn from these data [8,9,10,11,12]. Beyond the practical and financial costs associated with replacing those lost to follow-up, ethical concerns need to be considered. If a trial is forced to extend recruitment and follow-up to achieve adequate power, the number of participants that may be exposed to unnecessary risks increases. Those trials unable to reach such power will also be less likely to confidently determine a treatment’s effectiveness, undermining the investment of participants.

Approaches to address consequences of poor of retention have typically involved statistical methods to deal with missing data [9]. Strategies to improve trial retention prospectively have largely focussed on trial participants, with many interventions developed and evaluated but little conclusive evidence on what works, and even less on strategies targeting trial staff [5]. In addition, whether these approaches address perceptions of participants who do not complete a trial is also in question. A qualitative evidence synthesis exploring participant reasons for drop out identified several themes that predominantly have to do with participants’ understanding and/or beliefs about their role in a trial and their “fit” in continuing [13]. It was suggested that not completing a trial may be influenced by inadequate consent processes that fail to set expectations with these participants [13].

For many trials, trial staff are expected to deliver information to potential trial participants during an initial recruitment consultation. This consultation should include sharing of information relevant to retention, such as the ability to withdraw voluntarily, the participant's responsibilities in the study, and the expected duration of their participation in the trial. However, how much of this information is communicated, and whether recruiters prioritise delivering that information, has been put into question [14]. In an analysis by Kearney et al. of patient information leaflets (PILs), only eight trials (16%) made any reference to the importance of patient retention or data collection and no PILs explicitly discussed the problems caused by incomplete data collection [15]. Only 17 trials (34%) described options for partial data collection to help retain patients and this information was not communicated consistently across corresponding trial documents [15]. An investigation into how retention information is communicated verbally during recruitment discussions has found a similar dearth of mentions [14]. Of the recruitment discussions analysed, 79% of them did not include any mention of retention and, among those that did, the conversation regarding retention only occupied 3% of the time in consultation [14]. There is then a need to further assess how recruiters are approaching discussions leading to informed consent that should, ideally, contain information relevant to participant retention.

Retention as a whole is comprised of many separate but interrelated behaviours (i.e., actions of individuals). For participants, behaviours can include returning questionnaires or attending clinic visits. For trial staff, that may include communicating with participants or entering outcome data. Methods from behavioural science can be used to understand what drives behaviour by defining key influences that contribute to that behaviour and how they interact. Those influences can include factors internal to the individual (e.g., motivations, attitudes, or beliefs) and external influences (e.g., environment, resources, or the behaviours of others) [16,17,18,19]. The Theoretical Domains Framework (TDF) has been utilised in the context of clinical trials to understand both participant and staff behaviours. The TDF is an amalgamation of 128 explanatory constructs drawn from 33 psychological theories that were deemed relevant to understanding and changing the behaviour of healthcare professionals [20, 21]. It was designed to simplify psychological theories relevant to behaviour change and to make it accessible to those looking to design or evaluate interventions [20, 21]. Newlands et al. used the TDF through qualitative interviews to identify barriers and enablers to trial participants returning questionnaires and/or attending follow-up at clinics [22]. Ellis et al. and Guillot et al. both used TDF-based interviews to assess barriers and enablers amongst clinicians to refer/enrol patients to clinical trials [23, 24]. This current study aimed to use the TDF and explore the behavioural influences on trial staff’s behaviour with regard to retention in trials. Our objectives were to identify which barriers and enablers to retention were relevant to staff within the context of their roles in trials. In particular, we sought to identify those barriers and enablers to retention that exist during the recruitment process and their perceived influence on trial follow-up success.


Specification of the target behaviours

Sufficient specification of the behaviour under investigation is paramount to a successful application of behavioural theory [25, 26]. One of the frameworks that has been used to specify trial specific behaviours is the Action, Actor, Context, Target, Time (AACTT) framework [26].The AACTT framework was used to specify the target behaviours of this study and are presented in Table 1.

Table 1 AACTT specification of target behaviour of each interview set

Participant identification

Two cohorts of trial staff were interviewed in this study. The first cohort, hereafter referred to as “retention staff”, were trial staff members primarily involved in the process of retention (i.e., issuing questionnaires, contacting participants for follow up data, oversight of trial retention activity). These retention staff were interviewed on their perspectives on retention more broadly. The second cohort, hereafter referred to as “recruitment staff”, were trial staff members who were primarily involved in having conversations about trial participation with potential participants. These recruitment staff members were interviewed on their perspectives specifically on discussions of retention information during informed consent. Each cohort was sampled from a different set of host trials, resulting in a high diversity of staff and trial experiences.

Retention staff

Ongoing trials with ‘poor’ retention (defined as those with more than 15% missing primary outcome data) were selected from the clinical trial portfolios of project contacts and also through adverts on social media. Trials were either actively in follow-up or had recently completed follow-up procedures. Five trials were selected purposively, all of which were phase III pragmatic effectiveness trials with adults consenting for themselves in non-emergency settings. Further details on trial selection and recruitment are published elsewhere [22, 27].

Trial staff (e.g., research nurses, trial managers, data coordinators) associated with the five host trials (which were set in within urology, frailty and aging, dentistry, and gastroenterology) were invited for interview. One-to-one semi-structured telephone interviews were conducted informed by the TDF topic guide. Verbal informed consent was sought from each participant before interviews commenced. All interviews were audio-recorded and transcribed verbatim by an external company.

Recruitment staff

Active trials were identified through known professional networks and social media. Trials could be from any speciality or design but needed to be a clinical trial in which adults consented under their own capacity. Clinical trials were defined as “any research study that prospectively assigns human participants or groups of humans to one or more health-related interventions to evaluate the effects on health outcomes” [28]. Trials needed to be either actively recruiting or have finished recruiting no longer than 12 months from the start of data collection. Trials included those in which recruiters were also tasked with follow-up procedures or in which they were primarily responsible for recruitment/enrolment of participants, but then handed off study follow-up to dedicated trial staff (e.g., a central trial office).

Participants were recruited from both eligible host trials and separately through known professional networks and social media. Those recruited through host trials were invited through an invitation sent via the trial’s central email account by supervising trial staff. Details of this study, along with a participant information leaflet and contact information for the study team, were included in the email. It was stressed to recipients that participation in this study was voluntary but that it was approved by the trial’s steering committee and would not adversely impact their work if they chose to participate or not. Participants recruited through other means (i.e., those not employed through a host trial) contacted the study authors to indicate their interest in being interviewed. A participant information leaflet was forwarded via email and any questions were answered either via email or immediately preceding the interview. Verbal informed consent was taken before the interviews commenced. Interviews were conducted remotely via video call (i.e., Microsoft Teams). Interviews were audio recorded and then transcribed verbatim by an external company. These transcripts were checked for quality and de-identified.

Data collection

Retention staff interviews

These interviews were conducted between 21/02/2019 and 02/04/2019 as part of a project titled “Systematic Techniques to Enhance rEtention in Randomised controlled trials” or STEER, the protocol for which is published [27]. An interview topic guide was developed using guidance on TDF-based qualitative techniques, as well as experience from the study authors in designing similar interviews [13, 14, 22, 27, 29, 30]. The topic guide was refined through group discussion, following AACTT specification of the study’s target behaviour. The topic guide was then piloted through mock interviews, after which it was further refined to optimise wording and flow of questions. The final version of the topic guide is available in Additional file 1. Interviews were conducted by a research fellow (RN) and the initial three interviews were assessed for quality by KG. Ultimately, the purpose of these interviews was to explore staff’s perspectives on why trial participants fail to remain on trial, as well as strategies or factors that promote retention. These interviews were not included in the analysis of the STEER study as their target for intervention development was the behaviour of trial participants, as opposed to staff. Accordingly, the content of these staff interviews presented an opportunity to be used within this current project to maximise its output and efficiency.

Recruitment staff interviews

Semi-structured qualitative interviews, informed by the TDF, were conducted for this group between the 24th of May and 19th of August 2021. An interview topic guide was developed using guidance on TDF-based qualitative techniques, as well as experience from the study authors in designing similar interviews [13, 14, 22, 27, 29, 30]. The topic guide was refined through group discussion, following AACTT specification of the study’s target behaviour. The topic guide was then piloted through mock interviews, after which it was further refined to optimise wording and flow of questions. One further iteration of the topic guide was completed after the initial three interviews following feedback from the study team. The final version of the topic guide is available in Additional file 1. Interviews were conducted by the study’s first author (TC) and the initial three interviews were assessed for quality by KG. The interviewer (TC) adapted the order of questions within the topic guide to facilitate the natural flow of conversation.

Data analysis

Interview transcripts were imported into NVivo qualitative analysis software (Version 12 [31]). Coding guides for each target behaviour were developed using the domains and constructs of the TDF and refined through group discussion. Coding was completed independently by one author (TC) and two transcripts from each interview set were double-coded by another (ED) to assess fidelity of the coding guide and quality of coding. These double-coded transcripts were reviewed during a group meeting to discuss any discrepancies and reach consensus between the coders. Verbatim data were coded into appropriate behavioural domains using the coding guide.

Once data were coded into domains, excerpts within these domains were reviewed to identify emergent beliefs across interviews. These beliefs were summarised into belief statements that captured the core narrative content of these utterances, with the associated domain (e.g., knowledge, skills, etc.) framing the structure of these statements. Belief statements were then analysed for emergent themes that captured similarities between these statements. These themes would provide higher level summaries of barriers and facilitators to the target behaviour that appear relevant across separate, but related, beliefs, and across different TDF domains. Both the belief statements and the resultant themes identified were reached through team consensus, with particular attention being placed on frequency, presence of conflicting beliefs, and the strength of beliefs [30].

For the purposes of a comprehensive analysis, a broad perspective on the target behaviour of retention to trials was adopted, as participants often spoke on the behaviour of others (e.g., other trial staff or participants) than exclusively about their own behaviours. The belief statements that will be presented were thus produced to differentiate the proposed actor(s) involved (e.g., I am confident [self], My colleagues don’t [other staff]).


The results presented here are reported per the Consolidated criteria for reporting qualitative research (COREQ) checklist. This checklist is available in Additional file 2.

Participant characteristics

Participant characteristics for both interview sets are presented in Table 2, with further detail provided in the following sections.

Table 2 Participant characteristics by interview set; NS = not specified; *Data is number in retention staff; recruitment staff

Retention staff interviews

For those interviews involving retention staff, participants represented four host trials. The trials were broadly within urology, frailty and aging, dentistry, and gastroenterology. The host trials included a range of interventions: two host trials were evaluating surgical interventions, one trial a pharmaceutical intervention, and the fourth trial was evaluating alternative monitoring schedules. All four trials used the same method of outcome data collection by requiring participants to return questionnaires through post, with one also requiring the attendance at a clinic visit. Follow-up timepoints ranged from singular follow-up at six months, to multiple timepoints from three to 24 months after participant randomisation. Information on how staff responsibilities were delegated (as reported below for recruitment staff) was not collected for these trials. A total of nine trial staff members were recruited and interviewed, with four members of staff from one trial, two members of staff each for two trials, and one member from the remaining trial. Their roles were: trial manager (n = 3), trial administrator/data coordinator (n = 3), and research nurse (n = 3). Time in their roles ranged from three weeks to 10.5 years (mean 5.4 years). Those that self-reported their gender (n = 7) all identified as women.

Recruitment staff interviews

Sixteen participants were interviewed, fourteen from across five host trials and two not associated with a host trial, instead identified through social media. These trials were broadly in 1) orthopaedic surgery, 2) urology, 3) sleep medicine, 4) dermatology, and 5) gastroenterology. As mentioned previously, all trials consisted of adults consenting for themselves and the trial outcomes were typically patient-reported but also included safety and economic outcomes, as relevant to their design (additional details on these host trials is available in Additional file 3). Trials varied in the breakdown of responsibilities across local and central sites. Trials 1, 2, 3, and 5 allocated a central study team to facilitate the collection of patient-reported outcomes that required participant input (i.e., questionnaires sent to participants). Recruiters in these four trials were still expected to monitor participants, typically through entering data from medical records into case report forms. Trial 4 tasked staff recruiting to also complete all follow-up (i.e., schedule and conduct follow-up visits and collect outcome data from participants). Participants predominantly identified as women (n = 12, 75%) and were employed as a research nurse at varying seniorities (n = 10, 62.5%). Other roles included research physiotherapist (n = 1), research fellow (n = 1), and consultant (n = 4). Average length in their roles varied considerably, ranging from six months to 22 years (mean = 6.4 years). Participants were involved in recruiting to a number of trials, with some involved in one to three trials and the highest being 20–25 trials (median = 5).

Overall findings

In total, 25 participants across the two interview data sets provided their experiences and beliefs about trial retention. Results are presented below within two overarching themes. Within the first overarching theme of “Critical components that comprise retention”, four themes were identified: “Retention is not an equal priority to recruitment”, “Effective relationships are key to retention”, “Communication is the cornerstone to promote retention”, and “A sense of agency informs the belief that what you do matters to retention”. Six themes were identified in the second overarching theme of ‘Verbal communication of retention information at consent’, these were: “Recruiter reflections on their practices and overall trial retention”, “The importance of trying to contribute to retention”, “Being responsive to the individual guides the conversation”, “The practices that guide the conversation”, “Personal experience(s) and its influence on future conversations”, and “Trial-specific and general work-related factors that influence recruiters’ ability to have effective conversations”. The overarching themes and their individual themes are presented in detail below.

Critical components that comprise retention

This theme recognises that retention is defined not as a distinct action but as a grouping of separate and related actions that contribute to the outcome of retention. In other words, none of these actions by themselves are sufficient to be considered as retention but all can be considered necessary to achieve retention. This overarching theme includes data from across both sets of interviews (N = 25), as both sets of participants offered perspectives that can be included as contributing or restricting efforts to achieve retention. TDF domains are listed in parentheses next to each theme when described below. The belief statements that contribute to these themes are listed in Table 3, along with their associated TDF domain and illustrative quotes for each belief statement.

Table 3 Themes describing what constitutes retention and the associated belief statements; RET-00 = retention staff participant ID, REC-00 = recruitment staff participant ID

Retention is not an equal priority to recruitment (Knowledge, beliefs about consequences, social professional role and identity, and behavioural regulation)

What retention encompasses, and what leads to “good” or “bad” retention, seems to be less well understood compared to analogous processes within trial recruitment. Staff demonstrated an awareness that recruitment is often given a higher priority to retention in the way it is operationalised and incorporated into the specific roles within a trial and the research culture present at an institution. On a practical level, this can mean that staff are not sufficiently informed on the strategies that may be available to them to promote retention. For example, staff indicated that full participant withdrawal is often defaulted to, even where alternative means of participation are available that would allow outcome data to be collected in some form. Staff were also unsure of how effective existing strategies of retaining participants were.

Staff also indicated that there were tensions among research teams regarding who actually carried responsibility for retention. Roles may be more strictly demarcated in some trials or institutions, leading to a less holistic view of one’s contribution towards a trial’s success. When considering possible ways to ameliorate both these practical and cultural issues within trials, training that focused on retention was suggested. This included raising a general awareness about the importance of retention and the implications of poor retention, redefining roles within the trial to encourage a synergistic view between separate teams, and instruction on retention strategies available to the team and the evidence supporting those strategies.

Effective relationships are key to retention (Skills, beliefs about consequences, social influences, and reinforcement)

Trials were acknowledged as an inherently interpersonal endeavour and the need to nurture such relationships was viewed as fundamental to their success. A key skill that was emphasised by staff was the ability to form and maintain effective relationships with participants. These relationships were believed to precipitate a shared sense that participants are partners within a trial and participant contributions should be acknowledged. Staff often pointed to these interpersonal elements as potent incentives that motivated them as trial staff to retain. They emphasised that being able to have such relationships was an important aspect of what they enjoyed about their role in trials. Positive relationships with other staff members were also seen as contributing to retention success. Open and collaborative relationships between members of local teams and trial colleagues in other centres fostered beliefs in staff’s ability to engage effectively within their own roles and respond to challenges.

Communication is the cornerstone to promote retention (Skills, beliefs about consequences)

Staff presented strong beliefs in the efficacy of communication in their roles and its influence on retention. Staff who had a more active role in retention advocated for the importance of participants receiving adequate information about follow-up during informed consent. There was a belief present amongst these staff members that those recruiting may not be doing so and that those tasked with retention were facing the repercussions of this. The recruiters interviewed (who were from separate host trials from the staff mentioned above) echoed the importance of communicating follow-up information in their consent discussions. Many emphasised that it is essential that they do so, but some did admit they may not do so to a degree that is effective.

Expectation setting was one of the main goals put forward by staff as to why communication of follow-up information with participants about what they will be doing as part of the trial is essential. At consent, and throughout the study, it was advocated that staff help participants to understand what is expected of them, how the trial differs from usual care, what the trial procedures entail, and how often they occur and how long they take to complete. It was believed that, by not doing so, participants would be unprepared or otherwise dissuaded from continuing their participation.

A sense of agency informs the belief that what you do matters to retention (Goals, environmental context and resources, behavioural regulation, intentions, and emotions)

Perhaps one of the most diverse themes, in terms of the breadth of opinion, was whether staff believed they had any substantial impact on retention. Predictably, staff who had less of a direct role in follow-up (i.e., were recruiters) presented with less confidence that they could influence retention. However, even amongst those staff tasked with follow-up, one’s ability to influence retention seemed to depend on a perceived sense of control over those outcomes. Staff often discussed the importance of trying to accommodate participants to improve retention. This included adapting ways of working, finding suitable alternatives to collect data, and generally to remain flexible. This staff flexibility was facilitated by the flexible follow-up options that were allowed within a trial. The ability to make necessary changes to the follow-up schedule, location, or procedures in order to accommodate the participant was noted as particularly effective in promoting retention.

Certain aspects of trial design appeared detrimental to staff’s confidence in their ability to retain. It was often mentioned that the design of particular documents could be revisited to better promote retention. This could be aspects of the consent form to emphasise follow-up, to both staff and potential participants. The length or complexity of questionnaires was also described as a barrier. Staff believed that participants were lost when questionnaires were unnecessarily long or contained questions that were not relevant to them or their allocated treatment. Questionnaires that were only as long as needed, formatted to allow simple answers, and easy to return (either through electronic means or pre-paid postage and envelope provided), were advocated to improve retention. Potential changes to how questionnaire data are collected were also suggested. This included translated versions in areas of non-native English speakers or the option to complete questions over the phone with staff.

Where staff appeared most unclear on their relative influence often had to do with factors intrinsic to their participants. Participants’ competing “real life” priorities were often cited as detrimental to retention. It was evident that these competing priorities were not always offered by participants as reasons for dropout and that could lead to frustration for staff who cannot link their efforts to retention. Similarly, it appeared to frustrate staff when their motivation to keep someone engaged in a trial was not met with similar motivation from the participant. The motivation of the participant was described as one major factor in retention that was relatively outside the ability of staff to influence.

Verbal communication of retention information at consent

The results presented below represent the perceived barriers and facilitators to communicating follow-up information to potential participants at the time of consent and is thus restricted to the second set of interview participants involved in recruiting (n = 16). These interview participants were primarily tasked with recruiting to trials, but some were also involved in collecting follow-up data, to varying degrees. Themes and their associated belief statements, along with illustrative quotes for each belief statement, are provided below in Table 4.

Table 4 Themes describing the overarching theme of communication of retention information at consent and associated belief statements; REC-00 = recruitment staff participant ID

Recruiter reflections on their practices and overall trial retention (Knowledge, skills, beliefs about capabilities)

The range of definitions of retention volunteered by interview participants was broad and varied in the specific detail given. Some participants, notably the consultants, had concise descriptions that defined retention as a trial participant completing follow-up through the associated primary outcome measure. Others offered comprehensive descriptions that included their own responsibilities, those of the trial participant, and why retention is important for a trial, along with the aforementioned completion of follow-up data.

Interview participants were predictably knowledgeable on the follow-up procedures and schedules of their trials, even when they were not directly tasked with that follow-up. They were able to give examples of how they believed they communicated this knowledge during their consent discussions and were typically confident in their ability to do so effectively. There was also a general sense that recruiters attempted to stay informed on the overall progress of the trial and rates of retention, including what strategies were implemented to ensure success in retention. However, some did admit to an unawareness of any issues in retention. They attributed this to a separation in their role from follow-up and conceded this did not mean such issues were absent but rather that they had not been brought to their attention. When asked about what was known generally to drive retention in trials, some participants referenced research on retention, or lack thereof, whilst others mentioned analogous research on recruitment. This was echoed when discussing the training that they had received in trials. A subset believed the training they received to not have covered anything specific to promoting retention. Alternatively, some answered affirmatively that they had been trained to promote follow-up but either did not offer detail on what that meant (e.g., whether strategies were discussed) or seemed to lack confidence in their answer. Those who did offer detail on their training often cited known courses in good clinical practice (GCP) offered by the National Institute for Health Research (NIHR) or other sponsors.

The importance of trying to contribute to retention (Intentions, beliefs about consequences, optimism, reinforcement)

Regardless of their training, recruiters nearly universally believed their role within the trial pathway to be important to retention. Often, they believed discussing follow-up was necessary in their consent discussions and that consent would only be valid if trial participants received an adequate explanation of that follow-up. There did not seem to be a clear consensus amongst recruiters how much of an impact their discussions of follow-up had on retention. Some expressed optimism that it would, whilst others were unsure or felt they had no impact. For those who felt they had some degree of impact on overall retention, there appeared to be a sense of professional pride that motivated them to have these follow-up discussions. They acknowledged the rewarding aspect of feeling as if one has contributed to the success of the trial through their own efforts.

Being responsive to the individual guides the conversation (Social influences, social professional role and identity, skills, goals, beliefs about consequences, beliefs about capabilities, emotion, environmental context and resources)

Recruiters are acutely aware of the human aspect of trial recruitment and moderate their discussions with potential participants accordingly. The idea that “no two approaches should be the same” was recurrent throughout the interviews. Recruiters often saw their role was to be transparent with a potential participant. They felt that they needed to be able to set and manage expectations about follow-up with participants from the time of consent. This was done by trying to highlight to participants what their commitment to the trial means for them as an individual and how that contributes to the larger success at the site and the trial as a whole. That included being pragmatic in discussing the follow-up appointments and procedures, so participants are fully informed and prepared for a certain level of involvement on their part. However, this information needs to be delivered with respect to the idea that these consent conversations can involve the dissemination of large volumes of information. Recruiters often felt the need to balance their conversations so that this level of information did not become burdensome to participants, especially at the cost of dissuading them from considering participation.

In order to have this balance, it was emphasised that recruiters should be able to assess a participant’s level of comprehension. Recruiters often said that they had to incorporate real-time assessment of a participant’s understanding of follow-up, along with the other necessary aspects of trial participation. This skill was admitted to be challenging to develop and those who were unsure of their ability to make these assessments were less confident in the effectiveness of their consent discussions. These consent discussions were said to be challenging at times, particularly if one was approaching a potential participant when they were unwell. The limitations of an individual’s attention and memory when unwell were cited as reasons recruiters may feel it inappropriate to cover all aspects of follow-up and instead prioritise what is necessary and deemed relevant to the potential participant.

Recruiters were also concerned about the implicit pressures that some individuals may feel to participate in a trial. In difficult contexts, like life-changing injury or chronic illness, recruiters described the need to be further cognisant of their potential influence and present trials impartially. Indeed, consenting under such potentially coercive circumstances was believed to be not just unethical but also lead to poor retention. In order to ameliorate potential pressures, and as an essential point to convey regardless, recruiters sought to emphasise that the trial was voluntary and that they were free to withdraw at any time. Additionally, they often advocated the support available to participants of a trial. The care received in a trial was promoted as being complementary to their typical care, with value added in the research team’s attentiveness and appreciation for the participant’s contributions to the trial.

The practices that guide the conversation (Behavioural regulation, environmental context and resources, memory, attention, and decision processes)

Recruiters reported a range of ways to prepare for their consent conversations. They reported reviewing trial documents, like the protocol or participant information leaflet. These same documents were often used during the conversation itself to guide the flow of discussion. Recruiters also mentioned having “mental checklists” for the information they want to discuss. More often, these mental checklists appeared to be a product of experience, potentially freeing up attention resources to be re-directed at responsivity towards the participant.

Personal experience(s) and its influence on future conversations (Beliefs about capabilities, skills, reinforcement, behavioural regulation, memory, attention, and decision processes)

As alluded to above, experience seemed to be linked to an ability to remember more easily what to discuss about follow-up during consent. Recruiters often mentioned that experience in their role serves to define their confidence in discussing follow-up and their preferred methods to approach those discussions. These methods appear to be trialled and refined through self-reflection on their behaviour and its outcome. Reflection with colleagues was mentioned less frequently, as the solitary practice of recruitment does not afford such opportunities. This reflection could often be precipitated by difficult or negative prior experiences with recruitment conversations. In some cases, recruiters were able to identify issues within the consent conversation immediately after and integrate these reflections. In other cases, issues did not become apparent until later in follow-up when staff and participant conceptions of trial commitments conflicted.

Trial-specific and general work-related factors that influence recruiter’s ability to have effective conversations (Environmental context and resources, beliefs about capabilities, memory, attention, and decision processes, social professional role and identity)

The interviews identified several factors outside the control of the recruiter that have a notable effect on their perceived ability to carry out recruitment conversations that include discussions of retention. The design of the trial was mentioned often as having considerable influence on how these conversations are structured. Those that are focused on patient-reported outcome measures, as opposed to safety/efficacy etc., align the scientific priorities of the trial with the expectations required from participants. This seemed to facilitate retention discussions as recruiters feel they do not have to balance the abstract goals of trial outcomes with the treatment priorities of the participant. The relative complexity of follow-up also, understandably, impacts on recruiter’s confidence. A trial that presents frequent and/or invasive outcome measures are considered more difficult to “sell” to a participant. Those trials with more involved follow-up place strain on the memory/attention capacity of recruiters (and participants), along with straining the time limits of the consultation. These time limitations are further complicated by the competing work pressures faced by recruiters. And, finally, the extent of recruitment conversations is subject to who in a research team makes first contact with a potential participant. Some recruiters start their recruitment process with a participant who has first met with a consultant. These consultant conversations vary in their content, but typically focus on the treatment pathway, with less attention paid to the trial pathway. Recruiters then pick up this aspect of the conversation. In contrast, other trials are designed in such a way that recruiters have initial contact with a potential participant and thus a higher degree of control on the extent of trial-relevant communication.


This study has identified key perspectives from trial staff on the behavioural influences to trial retention at the point of initial recruitment discussions of informed consent and more broadly. These perspectives come from both staff involved in retention directly and those more involved with recruitment. By drawing on the experiences of a wide range of trial staff, in role and in tenure, we have expounded on the complex interplay of behaviours important for recruiters, their colleagues, and trial participants.

The themes generated fall broadly into two overarching themes, those relevant to the full range of staff roles interviewed and those specific to the recruiters interviewed. The former theme identified that retention in trials does not seem to be given equal weight to recruitment, which is echoed by the dearth of methodology research on retention in favour of recruitment [4,5,6]. This imbalance appears to be reflected in the training offered to trial staff, with an emphasis on assessing medical eligibility and reaching suitable benchmarks for ethical consent, but perhaps at the expense of practical considerations that promote retention. In particular, staff that may be isolated from the day-to-day practices of follow-up due to trial design could underestimate the impact of their contributions to retention. Opportunities for recruiters to contribute positively to the probability someone is retained may be neglected in favour of the other aspects of the trial they have been trained to cover. More troubling are the behaviours detrimental to retention that are not addressed with alternative best practices. Such gaps in training may also explain why some of our participants demonstrated uncertainty, or outright pessimistic views, about their contributions to retention. Even for those staff tasked with follow-up, uncertainties on the effectiveness of their retention strategies demonstrates a potential lack of training and/or further reflects a lack of available evidence on effective retention strategies.

From interviews in this study, a sense that one’s behaviour is effective in contributing to retention is predicated on the weight attributed to factors outside the influence of their behaviour. Staff clearly demonstrated their motivations to work with their participants to keep them involved in the trial, but these efforts were moderated by the motivations and priorities of the participants themselves. Key elements to successful retention noted by our participants often described elements that could feasibly modulate the motivations and priorities of trial participants. The recurrent emphasis we witnessed on the quality and timing of retention-relevant communication, along with the quality of the relationships formed within trials, points to these interpersonal aspects of trial roles as potent potential levers for aligning discordant motivations and priorities throughout a trial. Gaining perspective on participant motivations and potential mechanisms for positively influencing these motivations has been identified by trial stakeholders (participants and staff) as important targets for further methodology research [3]. The perspectives of our interview participants address five of the top 10 priority questions set by this stakeholder group (Q1. What motivates a participant’s decision to complete a clinical trial; Q4; What are the best ways to encourage trial participants to complete the tasks (e.g., attend follow-up visits, complete questionnaires) required by the trial?; Q7. What are the most effective ways of collecting information from participants during a trial to improve retention?; Q8. How does a participant’s ongoing experience of the trial affect retention?; Q9. What information should trial teams communicate to potential trial participants to improve trial retention?) as seen in Table 5 [3].

Table 5 Mapping of findings to PRioRiTy 2 trial retention methodology targets [3]

For many trials, there is complex interplay between groups of individuals involved in delivery. Recruiters, regardless of their later roles, are a participant’s introduction to the social networks involved in running trials. They need to set realistic expectations about risks, potentially limited benefits, and commitments of time and effort that are required by the trial in order to be a participant. Recruiters have a restricted window to set these expectations but need to do so impactfully, particularly if they do not have ongoing contact with participants. It is here that recruiters should seek to highlight follow-up in a way that it reframes the sometimes-abstract trial outcomes to the perspective of the participant. Staff involved in follow-up could employ a complementary suite of behaviours supporting retention, providing ongoing management of a participant’s retention behaviours. Examples of such behaviours could include debriefing participants after appointments, discussing particulars of the next visit, or reminding them of the accommodations and support that the trial team can offer. Oftentimes, it was mentioned that this support required is based on relational aspects. The relationships between staff and participants rely on the social and communicative behaviours exercised by staff. Several staff mentioned that the relationships they form with their participants serves to reinforce their own retention behaviours. These results parallel findings on what relational aspects of trials are important to participants [32]. As our interview participants seemed to place a premium on the ability to establish and maintain effective relationships (echoed by other research with staff [4]), a perceived strain or breakdown in these relationships could have implications on staffs’ confidence in their roles. The knock-on effects from this disturbed confidence have the potential to exert detrimental effects at several points along the trial retention pathway. Taken together, our results demonstrate a need to further explore the impact of communication practices and relational factors within the context of trial staffs’ behaviour. Importantly, the interaction between this behaviour and their participants’ retention behaviour is a pivotal area to consider for possible intervention design. Pursuing such avenues towards effective interventions that address issues within retention will serve to fill gaps seen within the current evidence base. That gap is highlighted in the recent Cochrane review of retention interventions which identified very few existing interventions with even moderate-certainty evidence (4/70 interventions) and primarily low effect size (1–7% improvement in retention outcomes) [refworks crashed]. Overwhelmingly, those interventions (68/70) sought to intervene on participants which further leaves open the possibility that interventions aimed at staff may prove to be a severely undeveloped resource of moderate to high rates of improvement in retention outcomes.

Strengths and limitations

This study shares many of the same strengths and limitations of previous interview studies using the TDF. The structured approach to topic guide design and coding of data is useful in its systematic exploration of behavioural domains known to be relevant in understanding behaviours [30]. However, there are criticisms that this approach may restrict topics of conversation important to interview participants and the predominantly deductive nature of analysis prohibits including results that do not “fit” within these domains [33]. Efforts have been made in this study to utilise the topic guide flexibly to facilitate a more natural flow of conversation. Open-ended questions outside the TDF domains were also included to prompt interview participants to discuss topics not already addressed by the topic guide. Similarly, the analysis was carried out in both deductive and inductive phases to capture as much pertinent data as possible. Our studies made use of behavioural specification guidelines when identifying the target behaviours for each interview set to facilitate efforts in interpretation and replication by others. However, interview participants did not always cooperate with our intended defined boundaries of behaviour when discussing their experiences. As such, an inclusive approach to the target behaviour of “retention” was adopted to make use of such data. Data was also generated within our specific target behaviour of “retention communication at consent” to allow analysis within this more narrowly defined context. We believe this two-pronged approach to behavioural specification in analysis has allowed for a more comprehensive approach. This is particularly important in the context of these studies as they aimed to explore a relatively unknown area of methodology research.

A potential limitation of the data set could be that the main author (TC) was not involved in the planning or conduct of the first set of interviews. However, as other members of the research team were directly involved with the implementation of this prior study, there is a marked consistency in the conduct and quality of both studies, complemented by integrated, independent analysis of one set of data. The interviewer in that (RN) study was consulted prior to the second interview set was conducted and was available throughout for questions regarding the context of the first interview set [22, 27]. Topic guides and coding guides for the first interview study served as references for the development of the analogous documents in the second interview study, which further aligned their conduct.

Our study sample, while notably diverse, is still subject to the limitations of self-selection bias and a relatively small sample size. Trials involved in this study, and the staff recruited, may be comprised of individuals who are particularly motivated in their roles and so may not be representative of the larger trials community. In addition, as our host trials were solely pragmatic effectiveness trials, we cannot speak to the possible reasons behind non-retention in other types of trials, such as early phase trials where the influences on staff involved in recruitment discussing retention will likely differ. Future work on the feasibility and acceptability of any interventions generated from these results will look to counteract this by soliciting the opinions of those outside our sample. However, a strength of our study sample is the breadth of experience cited by our participants and in the diversity of the trials that they have gained that experience from. Ideally, this diversity will confer a generalisability of our results and a wider applicability of the interventions produced.


The themes generated in our interview study present the barriers and facilitators to retention from a breadth of roles and levels of experience in trials. As the consequences of poor retention present a threat to the validity of any trial, our research aimed to elucidate the complex mechanisms underlying its success or failure. Key findings add detail on the behavioural impact of preoccupation towards recruitment, elaboration on the roles staff believe they play towards retention, and, most importantly, perspective on how staff look to excel in those roles through successful communication and rapport development. Future efforts should focus on intervention development based on these findings to improve how trial staff involved in recruitment enable discussions about trial retention during informed consent.

Availability of data and materials

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.



Action, Actor, Context, Target, Time


Accident and emergency


Acceptability, Practicability, Effectiveness, Affordability, Side-effects, and Equity


Clinical Trial of Investigational Medicinal Products




Good clinical practice


General practitioner


Participant (patient) information leaflet


Patient-reported outcome measure


National Health Service


National Institute for Health Research


Standard Protocol Items: Recommendations for Interventional Trials


Study within a trial


Theoretical Domains Framework


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The authors would like to thank Rumana Newlands (RN) for her work in conducting the first set of interviews and support in accessing that data. We would also like to thank Louisa Lawrie for helping to provide training to TC in the analysis of TDF interviews.


TC held a PhD linked to the Trials Methodology Research Partnership funded by the Medical Research Council UK and National Institute for Health research (MR/S014357/1). The study that generated data for interview set two was supported by the Chief Scientist Office of the Scottish Government Health and Social Care Directorates (Grant number CZU/3/3). The Health Services Research Unit, Institute of Applied Health Sciences (University of Aberdeen), is core-funded by the Chief Scientist Office of the Scottish Government Health and Social Care Directorates. They were not involved in the design of the study or the collection, analysis, and interpretation of data.

Author information

Authors and Affiliations



TC contributed to the conceptualisation of the study, was responsible for the design and conduct of the second set of interviews, the analysis of all data, and was the primary author of the manuscript. ED provided expertise in the development of the TDF interview topic guide and throughout the coding and analysis. KG contributed to the conceptualisation of the study, provided the data from the first set of interviews and provided expertise in the development of the TDF interview topic guide and throughout the coding and analysis. ED, KG, and HM all provided ongoing training to TC on the conduct of interviews, assessed interviews and coding for quality, and contributed edits and final approval of the manuscript.

Authors’ information

TC is a PhD student within the Health Services Research Unit at the University of Aberdeen and this manuscript is part of his larger dissertation work. To date, this work also includes a mapping review on applications of behavioural science to recruitment and retention to clinical trials [34]. The results of this manuscript and the review will feed into the next phase of the PhD project, which will be to design behavioural strategies to address barriers to retention in clinical trials.  

Corresponding author

Correspondence to Katie Gillies.

Ethics declarations

Ethics approval and consent to participate

Participants taking part in the interviews were consented via an informed verbal consent script (approved by North of Scotland Research Ethics Service (NoSRES) Committee (ref: 17/NS/0086) and the University of Aberdeen College Ethics Review Board (CERB) (Application No. 2007, Title: CERB/2020/12/2007)). The recordings were not started until the participant first gave permission to the interviewer to start that recording. These recordings were then sent via secure file transfer to an external transcription service contracted by the study team. Transcripts were generated, participant identifiers removed, and returned to the study team via secure file transfer. The study team then went through an additional deidentification of the transcripts to remove trial names, places of employment, etc. Both identifiable and de-identified data, in the form of recordings and transcripts and their associated meta-data, were stored on secure University of Aberdeen servers and only accessible to members of the study team.

The study that generated data for interview set one was granted ethical approval by the North of Scotland Research Ethics Service (NoSRES) Committee (ref: 17/NS/0086). The study that generated data for interview set two was approved by the University of Aberdeen College Ethics Review Board (CERB) (Application No. 2007, Title: CERB/2020/12/2007) on 17/02/2021. Approval by host trial steering committees was also confirmed and records of those communications stored for posterity. All methods were performed in accordance with the relevant guidelines and regulations.

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This paper does not contain any individual person’s data in any form as they have been appropriately anonymised.

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The authors declare that they have no competing interests.

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Supplementary Information

Additional file 1.

Topic guides for interviews. Final versions of TDF topic guides used in interviews is provided. Two topic guides are available in the file. The first is the topic guide for the retention staff interviews, the second is for the recruitment staff interviews.

Additional file2.

COREQchecklist. Completed COREQ checklist for the manuscript.

Additional file 3.

Additional detailson host trials. Table giving additional details on the five host trials sampledfrom for the recruitment staff interviews. Data is populated to provide contexton the trial outcomes and delegation of staff responsibilities.

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Coffey, T., Duncan, E., Morgan, H. et al. What influences communication about retention in randomised trials: a multi-trial, theory-based analysis exploring trial staff perspectives. BMC Med Res Methodol 22, 231 (2022).

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