Why participant recruitment remains the biggest challenge in clinical trials

Clinical trials are essential for advancing medical research and developing new treatments and therapies, yet they all face the same significant hurdle: participant recruitment. Approximately 80% of all clinical trials fail to meet their initial enrolment target on schedule, leading to delays and the costly addition of new study sites, with some resulting in lost revenue of as much as 8 million dollars per day for drug-developing companies (1).

Successful trials depend on not only recruiting a sufficient number of participants but also retaining them from the study's initiation to its conclusion. Statistics reveal that a staggering 85% of trials struggle to retain enough participants, with an average dropout rate hovering around 30%. Additionally, the majority of trial sites, over two-thirds, fail to meet their initial participant enrolment targets.

In some cases, up to 50% of these sites enrol either one or no participants at all, underscoring the widespread difficulties faced in recruiting participants for medical studies (2). In the United Kingdom, the NHS has reported a 44% drop in participants recruited to commercial clinical trials in the past five years (3).

These figures highlight the complex landscape of recruitment and retention issues and the need for innovative approaches. Without adequate recruitment and retention, the participant pool for a trial may be too small to yield conclusive results and potentially undermine the trial's objectives.

What are the challenges?

Participant recruitment is a complex process, and there are multiple reasons why it remains such a pervasive challenge. These include factors like public awareness, logistical issues, strict eligibility criteria, ensuring diversity, participant funnel at site, regulatory barriers, and, once you have successfully recruited enough participants, retention becomes a primary challenge to the success of a trial.

Lack of awareness

A lack of public awareness about clinical trials is one of the primary obstacles to participant recruitment. Many potential participants are either unaware that clinical trials exist or don’t understand their importance. This gap in awareness can be attributed to limited outreach, as many clinical trial opportunities are not widely advertised, making it difficult for potential participants to discover them. Additionally, fears about the safety of experimental treatments deter many, and the scientific and medical jargon used to describe trials can be daunting, making it harder for the general public to grasp the benefits and importance of participation. The lack of immediate benefit also discourages many participants, as they may not receive direct benefits, particularly in placebo-controlled trials where some participants receive no active treatment.

Logistical barriers

Even when individuals are aware of clinical trials, logistical issues often impede their ability to participate. For instance, clinical trials are frequently conducted in specific medical centres or hospitals, which may not be accessible to everyone. Participants may need to travel long distances, which can be costly, inconvenient, or impractical for participants with severe health conditions. The time commitment required is another barrier; participating in a clinical trial often necessitates a considerable time investment, with regular visits for treatment, monitoring, and follow-ups potentially interfering with personal and professional responsibilities. While some trials offer compensation, many do not cover all associated costs, such as time off work and childcare. This financial burden can deter potential participants, particularly those from lower-income backgrounds.

Strict eligibility

Clinical trials also have strict eligibility criteria to ensure the safety and reliability of the study results. These criteria can significantly limit the pool of potential participants. For example, trials often require participants to have a specific diagnosed health condition at a particular stage, which can make it difficult to find suitable candidates. Demographic requirements further narrow the pool, as some trials aim to study effects within certain demographic groups, such as age, gender, or ethnicity. Often, participants' medical histories must align with the trial’s requirements, and circumstances such as pre-existing illnesses, prior treatments, or concurrent medications can disqualify many otherwise willing volunteers.

Accessibility

Ensuring diversity in clinical trials is crucial for the development of effective and safe treatments for a wide range of populations. Diverse participant pools help ensure that the findings of a trial are applicable to various demographic groups, including different ages, genders, ethnicities and the neurodiverse.

However, achieving diversity in clinical trials is challenging. It can often require targeted outreach and engagement strategies to overcome mistrust and ensure that underrepresented groups are informed and encouraged to participate. Trials must be designed with inclusivity in mind, considering factors such as cultural sensitivities, language barriers, and varying levels of access to healthcare resources.

Location

Site selection is another critical aspect that significantly impacts the success of clinical trials. Choosing appropriate sites involves identifying locations with sufficient participant populations, necessary infrastructure, and experienced clinical staff. Urban centres often provide access to larger, more diverse participant populations and advanced medical facilities, but they might not be accessible to participants from rural areas. Conversely, rural sites may have unique participant populations and less competition for trial participants, but they often face challenges such as limited medical infrastructure and resources.

Effective site selection requires a balance between accessibility for participants, the ability to meet trial requirements, and the potential for high enrolment rates.

Regulation

Regulatory barriers present another significant hurdle in participant recruitment for clinical trials. Each country and region has its own regulatory framework governing clinical research, which can lead to complex and time-consuming approval processes. These regulations are designed to protect participant safety and ensure ethical standards, but they can also delay the initiation of trials and limit the types of studies that can be conducted.

Navigating these regulatory requirements requires substantial resources and expertise, which can be particularly challenging for smaller contract research organisations (CROs).

Participant Retention

Finally, once you have recruited a sufficient number of participants, the focus must then turn to participant retention, which presents its own challenges. Retention is a crucial factor in the success of clinical trials, as high dropout rates can compromise the integrity of the study and its findings. Retaining participants throughout the trial period involves addressing various challenges, including maintaining engagement, ensuring consistent communication, and providing support for any logistical or personal issues that may arise. This is particularly important in more vulnerable patient populations, where the risk of drop-out may increase due to the chance of volunteers receiving placebo.

What are the solutions?

Addressing the challenge of participant recruitment in clinical trials requires an innovative approach that caters to the diverse needs of potential participants.

One crucial strategy is to enhance public awareness through comprehensive outreach campaigns. Utilising various media channels, including social media, local community events, and partnerships with healthcare providers, can help disseminate clear and accessible information about the purpose, benefits, and safety of clinical trials. Simplifying medical jargon and providing testimonials from past participants can further demystify the process and ease fears.

Logistical support is another key element in encouraging participation, which begins with understanding the participant’s needs. Offering transportation services, accommodation options, and financial compensation for time and expenses can make participation more feasible, especially for those from lower-income backgrounds. Flexible scheduling and the option for virtual visits can accommodate participants' personal and professional responsibilities, reducing the time commitment required for in-person visits. Additionally, making safeguarding a part of your recruitment message can assist in putting participants minds at ease. Confirming a caregiver, chaperone, or female/male doctor is permitted or available, where necessary and possible, is vital to successful recruitment and retention.

Ensuring diversity in clinical trials is essential for obtaining comprehensive and applicable results. Targeted outreach to underrepresented communities, along with the involvement of community leaders and healthcare providers, can build trust and encourage participation. Where possible, remove or modify any criteria to help widen the recruitment funnel without compromising the study safety and endpoints.

Strategic site selection can further enhance accessibility and enrolment. A mix of urban and rural sites can reach a broader demographic, and collaborating with local healthcare providers and community organisations can enhance site selection efforts, ensuring that trials reach a broad and representative participant base. Identifying locations with sufficient participant populations and necessary infrastructure, while ensuring that sites are not too burdensome for participants to access, is key. Utilising community-based sites can also help in reaching more participants who may not have the means to travel to larger medical centres.

Sponsors and CROs must work closely with regulatory bodies, staying informed about changing regulations and seeking ways to streamline approval processes without compromising safety and ethical standards. Developing clear, consistent protocols and leveraging electronic regulatory submissions can reduce delays and facilitate smoother trial progress.

Maintaining participant engagement throughout the trial is vital to its success. If participants consistently drop out, then recruitment must begin again, leading to unnecessary costs and delays. Regular and transparent communication about the trial’s progress, addressing concerns promptly, and providing ongoing support can build trust and loyalty. Offering additional support services, such as mental health counselling, transportation assistance, and flexible scheduling, can also help participants manage any challenges they face during the trial. Building strong, trusting relationships between researchers and participants is essential for maintaining high retention rates and ensuring the success of clinical trials.

Decentralised or hybrid clinical trials

The adoption of decentralised or hybrid clinical trial designs, which became more prevalent during the COVID-19 pandemic, can significantly improve recruitment and retention. These trials use commonly available equipment, such as smart phones and laptops, to conduct trials remotely, minimising the need for participants to travel to specific sites. This approach is designed to support participant access, recruitment and retention, with research fitting into the lives of the participants. These trials can include telemedicine consultations, home delivery of study medications, and remote monitoring of participants’ health data. By reducing geographical and logistical barriers, decentralised trials can enhance accessibility and convenience for participants, increasing enrolment rates and retention.

What can MAC do to help?

MAC Clinical Research is uniquely positioned to address the challenges of participant recruitment and retention in clinical trials through a combination of advanced software, strategic site management, and participant-centric approaches.

Nicola Armitstead, Vice President of Site Clinical Operations, outlines what makes MAC exceptional:

Our bespoke recruitment and retention programme, MAC EnVision?, is made up of a specialised in-house recruitment team and a purpose-built engagement software platform to find accurately characterised, eligible participants with ease and precision.

Interested and potential patients are initially handled through our dedicated, multi-channel contact centre in the UK, with a large, highly skilled team focused on delivering the right patients for the right study. The contact centre service requests via telephone, email, text and webchat, aiming, where possible, to make the process as easy as possible for participants.

This streamlined process ensures that volunteers are expertly pre-screened according to your study’s inclusion and exclusion criteria and helps ensure a lower screen fail rate, enhancing the efficiency and success of our recruitment efforts.

Through our fully owned and operated clinical research sites, MAC is able to recruit more participants across fewer sites compared to traditional studies conducted in hospitals or care trusts by individual physicians or consultants. This method allows us to avoid the fragmented participant recruitment seen in traditional approaches, where few participants are enrolled at each site, necessitating the activation of many more sites to meet enrollment targets.

Having a fully owned network of sites gives us invaluable insight into delivering successful recruitment strategies that can be applied to our contracted site network across the globe. We also have access to extensive data sets, including NHS data, and targeted recruitment teams focused on each therapeutic area. Our database currently holds 230,000 potential participants. This comprehensive approach means that MAC Clinical Research can often meet and exceed the recruitment and retention needs of your clinical trial weeks ahead of schedule.

This acceleration in recruitment provides sponsors the opportunity to reach study endpoints sooner, reducing timelines and associated trial costs, ultimately benefiting sponsors and participants sooner. With a potential reach of almost 35 million participants across the UK, we are the largest and leading company for participant recruitment and study management services.

We employ effective techniques, such as clear communication and useful information, to assist patients and healthy volunteers from randomisation through to study completion. These techniques are key factors for successful participant retention. Recognising each participant as an individual, we understand that taking part in a clinical trial is an important decision. Our recruitment and retention efforts start long before a study commences and continue throughout the study to ensure both participant and sponsor satisfaction. Our friendly staff builds relationships with participants throughout the study duration, ensuring their needs and requirements are met. We continually gather feedback about their experiences to improve our participant management processes.

Alongside this, MAC maximises subject retention levels for the studies we run by continuously evaluating the reasons for participant withdrawal, using primary data from our participant feedback and secondary data from industry analysis. Most issues are resolved through simple communication methods. We provide all clinical trial participants with 24-hour telephone assistance, a participant-focused website, courtesy calls before appointments, transport arrangements to and from the clinics, and unrivalled hospitality while at the site.

In cases where recruitment has fallen behind schedule, a site was unable to initiate, or study data quality has been compromised, MAC frequently provides study rescue services.

For example, in a recent clinical trial with bulimic participants, MAC was brought in as a rescue site for timeline recovery. We successfully recruited 26 participants in a four-month period, with the rate of recruitment tripling after MAC sites were initiated.

Participant recruitment is likely to remain the most significant challenge in clinical trials, impacting not only timelines and costs but also the validity of the study. The complexities involved in recruitment, from public awareness and logistical barriers to regulatory hurdles and participant retention, require constantly evolving, innovative solutions.

At MAC, we are committed to addressing these obstacles, and our comprehensive approach helps ensure efficient recruitment and retention, enabling us to meet and exceed the needs of clinical trials while accelerating study timelines and bringing therapies to participants sooner. With a focus on individualised care and adaptive solutions, we continuously redefine the standards of participant recruitment and retention in clinical research.

If you would like to speak to us about our experience in this area, or if you would like to know more about our services for a study, contact us here.

Sources

(1) National Library of Medicine, 2020.

(2) Clinical Leader, 2012.

(3) The Guardian, 2023.