Maximize Your Participant Enrollment by Managing All Phases of Recruitment

We’ve identified six phases of the typical enrollment process for clinical trials. Each phase has specific goals and challenges that we highlight. To manage the enrollment process from start to finish, you need to monitor the data from each phase and identify and address problem areas as they emerge. In instances of multi-site trials, collecting and analyzing data from each location should be done, as problem areas are likely to be different between sites.

Phase 1: Sourcing participants


During this first phase of enrollment, the goal is to determine the number of participants that each study site can access. Typically we would define participants as someone that appears to meet inclusion criteria. 

It’s important to make sure that these numbers are based on the actual number of participants in internal databases or through physician referrals, and are not projections of how many participants a site may think they can access through advertising. Often external advertising campaigns conducted by sites are very unreliable because of a lack of expertise in advertising best practices. 


The main challenges at this phase are the accurate projection of enrollment numbers based on study site estimates, together with there not being enough suitable participants identified. Enrollment forecasting can save both time and money while reducing the time necessary to recruit qualified participants. 

Using a data-driven approach like Trialfacts’ Due Diligence process, the number of potential participants needed at each phase of enrollment can be identified early on and addressed accordingly. Using this process can also address shortfalls in the number of participants available through internal means without increasing the cost by adding on an additional study site.

Pro Tip: When you’re reviewing the number of participants you may have access to through internal databases and physician referrals, also make a realistic assessment of the likelihood of enrollment. Review the site’s previous enrollment results from other studies with similar criteria to gauge the level of participant interest.

Phase 2: Initial pre-screening


While often overlooked, initial pre-screening (not to be confused with phone screening) is an important step in the process as it identifies ineligible participants and removes those who are unwilling to comply with the study protocol from advancing further. 

At this stage, pre-screening can take two different formats depending on the particular recruitment strategy. The first is through online pre-screening done through advertising and other external inquiries. The second being a medical chart review of internal databases and physician referrals. Effectively managing pre-screening will significantly cut down on work that research coordinators have to do at later phases of enrollment because eligibility is already established.


Effective communication and asking questions that are clear and concise is a challenge during this phase. Without well-developed questions, participants will answer incorrectly or give up. At the same time, the user experience (ease of use, accessibility from a mobile device, ability to finish at a later time, etc.) is important as participants are likely to abandon the questionnaire if it’s confusing or challenging. Don’t use big words or medical terminology that isn’t easily understood. Try to keep your questions short and direct.

Pro Tip: Look to existing communication professionals you have access to and ask to involve them as you draft your questions. Consider testing different versions of each question before finalizing your online pre-screening.

Phase 3: Phone contact


During this phase, the speed of making a first phone call and any follow-up communication with participants is the primary concern. Research shows that interest starts to drop off within five minutes of a participant completing pre-screening. It gets significantly worse after one hour and then further deteriorates after one day. 

Persistence is also key, and sites should be prepared to follow up consistently with participants. It’s not unreasonable to use five follow up attempts as a minimum and to plan for up to ten calls to each participant. Sites should aim for at least a 70% contact rate.


The main challenge during this phase is the speed of initial contact and sites not following up enough times with participants. This process is time-intensive and staff resource heavy, and many study coordinators can’t add hundreds of calls into their schedule. 

These challenges can be addressed by using an external phone screening service, implementing a phone call appointment system, and using online pre-screening. Online pre-screening results in higher-quality participants with more interest in participating as they’re engaged through the stages of the enrollment funnel, and are educated about the study.

Pro Tip: Set minimum service standards that can be measured and evaluated. If your goal is to call participants back within 6 hours and the study team typically averages 12 hours, you can re-evaluate your recruitment plan or look at outsourcing.

Phase 4: Phone screening


Phone screening is more than just a process to determine whether a participant is both eligible and a good fit for a study. At this stage, study sites should focus on building a strong relationship with the participant , as this is the most critical factor in successful enrollment and retention. This can be done by ensuring the study site has excellent communication, sets and meets expectations, and intentionally builds trust with participants. Study sites should see at least 50% of participants passing phone screening and scheduling an initial visit assuming comprehensive and effective online pre-screening is in place.


Depending on the study protocol, the phone screening phase can be time-consuming. Some studies may require up to 60 minutes to ask participants the needed questions. These time issues can be addressed by adding more online pre-screening and providing detailed information upfront so that participants can self-select. 

Pro Tip: If more than half of participants are failing the phone screening phase, this is an indication that better online pre-screening is needed.

Phase 5: Screening visit attendance


Sites should be focused on scheduling participants quickly for their initial clinic visit after they’ve passed phone screening. Some studies may be at higher-risk of no-shows, particularly if they’re addressing a stigmatized condition, or if participants are younger. Fast turnaround time can help maintain a participant ’s interest and encourage participation.

No-show rates at this stage in the enrollment process can be costly in terms of both the time and site resources already invested. The goal should be to have a no-show rate between 0-10%.


At this phase of the enrollment process, losing a participant because they were a no-show is usually an indication that they don’t trust the study site. Trust can be addressed at earlier stages of the process as sites work to establish a relationship with participants. An effort needs to be made to maximize opportunities for contact directly with the participant during the initial contact and phone screening phases.

Pro Tip: Building trust with participants is essential to successful enrollment. Look for ways to build a rapport with participants as soon as they indicate interest in the study, not just when they attend the screening visit.

Phase 6: Clinic screening


Once a participant has made it to this final stage in the process, the site’s goal should be to complete the clinic screening and enrollment as soon as possible. It’s important to identify sites that have a higher clinic screen fail rate along with groups of participants that have a lower screen fail rate. At this stage you want to monitor the types of patients that are more likely to enroll in the study independent of the site location. These types of participants can then be prioritized in enrollment efforts.


Losing a participant at this final stage can be frustrating for everyone, especially site staff who have been working actively to recruit participants. If a site has a high failure rate during this final phase of enrollment, it may jeopardize the ability to complete the study. Use data to calculate how many more participants are needed, and consider if you can realistically recruit that many participants within your timeframe.

Pro Tip: Consider using a text messaging based reminder service or have a study staff member to call and confirm appointment times with participants.


By breaking down clinical trial enrollment into six phases it becomes much easier to manage the process from start to finish. When informed by data, enrollment funnels can be optimized to ensure that sponsors and study sites are maximizing every opportunity to enroll participants, which means a much higher likelihood of completing a study on time and budget.

Trialfacts uses a data-informed Due Diligence process to bring consistency and predictability to participant enrollment. Through this process we’re able to identify the right number of participants you need during each phase of enrollment to meet your goals. Schedule a call with us today for a no-obligation review of your enrollment needs.

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