Patient recruitment and retention are two enormous considerations for optimizing clinical trials. Even the most intuitive study design can be thwarted by the inability to obtain and retain the patient population necessary to conduct the trial.

Below, we will discuss common strategies for ensuring a clinical trial has the essential study participants to be successful.

Why Is Retention So Important to a Trial’s Success?

Study participant retention affects three fundamental components of a clinical trial’s success: time, money, and study validity.

Poor retention can significantly affect a clinical trial’s timeline. Trials depend on a certain number of recruited participants to detect any significant differences in the study intervention. Considerable participant withdrawal can delay a trial by months to years, leading to a variety of downstream negative consequences such as financial constraints.

Besides missing deadlines and prolonging a clinical trial past its initial proposed timeline, money starts to become an even more important consideration. Time is money in the world of clinical trials. Prolonging a trial due to recruitment and retention concerns can cost a trial thousands and sometimes millions of dollars.

Study validity can become a concern with retention issues as well. Insufficient data can jeopardize the potential results of a trial well before the trial’s anticipated completion date. Taking shortcuts or attempting to perform the study with fewer participants due to a low retention rate decreases internal validity of a trial and leads to less than optimal trial results.

What Are Some Common Reasons for Patient Dropout?

There are a variety of commonly reported reasons from study participants who withdraw from trials. Some of the most frequent reasons include:

  • Perceived lack of appreciation
  • Lack of understanding of the purpose of the trial
  • Misunderstanding trial expectations
  • Fear and anxiety from participating in a clinical trial
  • Refusing to comply with study protocol
  • Side effects
  • Scheduling conflicts
  • Forgetting or not adhering to study appointments
  • Travel limitations
  • Physical inability to make appointments
  • Financial constraints
  • Personal or family matters
  • Personal health not improving during the trial

In a survey asking about study participants’ experiences in a study, participants who withdrew had greatly different survey answers compared to retained participants. 

For example, nearly twice as many participants that withdrew claimed it was difficult to understand the informed consent form. Building on this lack of understanding, nearly 50 percent more retained patients were satisfied with the informed consent discussion. 

This disparity highlights the importance of designing patient-centric studies that prioritizes patient decision-making and discussion in an easy to understand, relatable way.

In addition, the survey highlighted that significantly more study participants who withdrew described study visits as “stressful” and “fell short of personal expectations.”

Once again, patient-centric protocols can dramatically improve the study experience for study participants. Treating participants similar to patients as a whole and not merely a number in a clinical trial can go a long way towards increasing study retention.

What Can Be Done To Improve Patient Retention?

Motivating patients to continue to participate in a clinical trial can be a multifaceted approach. 

Some of the most common approaches include manipulation of the study protocol, streamlining transport and patient experience at appointments, and showing appreciation and recognition of patient effort to remain in the trial.

Protocol Optimization

Well-designed study protocols are patient-centric in the fact that they put the patient first and consider their needs as much or more than the study itself. 

One way to optimize a protocol is to develop easy to understand, relatable consent and patient privacy documents. Being able to relate the purpose of the trial and express realistic expectations of trial risks and potential benefits are not only good practice ethically, but also create a trust between researchers and study participants.

Another popular method of improving the protocol to make it more patient-centric is to develop study-oriented educational materials that are easy-to-read and in the participant’s first language. Both practices can help a participant feel more involved in the trial.

On the other side of things, some protocols ask too much of study participants with too frequent phone calls and patient visits, leading to burnout and feelings of exploitation. While a consistent feedback loop between researchers and study participants can help with retention, too much can be counterproductive.

Site Selection

Another crucial design component of a clinical trial pertains to site selection in which the trial will be conducted. Multi-site trials have the advantage of multiple geographical locations to appease multiple areas and demographics of potential study participants.

Conducting a trial in geographically-favorable locations is conducive to higher patient retention. Sponsors should select sites based on an evidence-based feasibility analysis that will result in adequate infrastructure, resources, and personnel in a location near enough to the target study population.

Experienced investigators or clinical research organizations can help sponsors choose study sites based on these criteria, and they can also help budget funds to ensure study sites and personnel are adequately compensated and equipped to conduct the study.

Communication Strategies

Communication is key when conducting a clinical trial. Sufficient communication with study participants means keeping them involved with the trial with consistent updates, timelines, and changes to the progress of the study.

An institutional ethics committee (IEC) can be useful in determining approved recruitment advertising techniques such as newspaper, television, and radio advertisements, as well as creating a study participant database that can be used to inform participants and other colleagues about important details and updates from the study. Instituting a database has been proven to improve retention by keeping participants involved in the study.

Technology is another great, always expanding technique to communicate with study participants and improve retention. Texting, email, and telehealth visits have all dramatically improved the efficiency and availability of the study team communicating with study participants without requiring them to leave home.

In the end, patients that feel more active or included in the management of their own health in a study will be more compliant and less likely to withdraw. Reminder calls, appointment updates, and thank you notes, if done in excess or in an intrusive manner, can be really great tools to make participants feel important and included in a clinical trial.


While some clinical trial participants consent to a study purely for altruistic motivations, incentives in the form of money or other perks have proven time and time again to be the most effective factor in motivating patients to enroll and remain in clinical trials.

Incentives do not always have to be financial in nature, although adequate financial compensation is an important consideration for study designers to make sure the participant’s time and effort is respected. Other forms of incentivization can be travel costs such as taxis or flights, as well as hotel rooms for participants that travel long distances from home.

Other effective strategies for improving patient retention include:

  • Setting appointment reminders
  • Accommodating patient schedules
  • Promptly responding to study questions and concerns

Should We Plan for Dropouts?

Now that we’ve discussed why patient retention is so important and the most common reasons patients stay or withdraw from trials, should you plan for dropouts? 

Conceding that a percentage of patients will drop out is not accepting defeat or poor trial design. Some patients will withdraw no matter how well the protocol is optimized, so having realistic retention expectations at the beginning of a trial can be advantageous in the long run to avoid unexpected problems.

Industry benchmark data suggests that only about 1 out of 10 patients that are identified as a candidate for a trial end up even being randomized. With only 10 percent being randomized, another 18 percent of those patients will still drop out.

The solution for this problem is commonly analyzed as the “leaky pipe” analogy. The pipe is the clinical trial with the “holes,” or “leaks,” being the obstacles to patient retention. Fixing or managing these “leaks” is the key to success in preventing patient withdrawals.

In Conclusion

Patients withdraw from clinical trials for a variety of reasons. When possible, it can be helpful to get feedback from patients that withdraw from a trial in order to improve the patient experience.

Poor patient retention costs clinical trials time and money. Failing to meet targeted trial enrollment at the end of a study due to excess patient withdrawal can prolong studies and affect the interpretation of study results, so promoting retention utilizing protocol optimization, communication techniques, and incentives are imperative.

Ultimately, keeping patients motivated throughout the trial while meeting expectations and continuing to provide support and reasons to continue is essential to a clinical trial’s success.

How Can iProcess Help?

At iProcess Global Research, you can expect to work with exceptional teams and operations to provide cutting-edge research to help organizations with clinical trials. With over 17 years of experience, iProcess has specialists that can provide a high level of quality and competence to optimize clinical trial protocols to support patient retention and conduct feasibility analysis to ultimately promote clinical trial success.

Contact iProcess today to get a free quote.


Recruitment and retention of the participants in clinical trials: Challenges and solutions | PMC

Recruitment and retention in clinical trials of the elderly | PMC 

Principles of recruitment and retention in clinical trials | PMC