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Retention in Clinical Trials: Keeping Patients on Protocols

March 23, 2021

While patient recruitment is key to starting a clinical trial, patient retention may be more critical in ensuring the trial moves through the phases. Keeping participants in a trial ultimately helps keep a study on track, saving the site time, money and resources in the process. Any study delay can be harmful to the study and the site as a whole.

Since going through a clinical trial is a voluntary process, participants have the right to exit the study at any given time, without any given reason. Participants may drop out of a study for an unavoidable reason, however, many of the reasons participants leave a study are preventable.

This infographic provides insights to average dropout rates, reasons dropouts occur and solutions for better patient retention.

Infographic for Retention in Clinical Trials: Keeping Patients on Protocols (full text below)

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It’s clear there’s a need for more effective ways to keep patients on protocols. While some dropouts will always be inevitable, it’s crucial to prevent both study delays and missing study data for regulatory submissions. When possible, understanding why a participant chooses to discontinue a study is valuable information to obtain. Their feedback may provide insight into what changes can be implemented to improve the patient experience.

How should we plan for dropouts?

Seven of 100 known patients from the top of the funnel complete the trial. 18% of patients randomized end up dropping out.

The “Leaky Pipe” Analysis¹

The “typical” funnel shows the process of patient participation and is used to identify gaps and find where to “fill the funnel” or “manage the leaks.” Industry benchmark data suggests that on average across all protocol phases and therapeutic areas, you need to identify ~10 patients to randomize 1. (The Leaky Pipe Analysis was contributed by Beth Harper of Clinical Performance Partners, Inc.)

Here’s an example of the funnel:

What are some common reasons dropouts occur? 

Some common reasons are:

Or, the patient simply changed their mind (it is their right to do so). Multiple factors can play a role in one’s decision to drop out, and each patient has their own circumstances and motivations. Some of these factors are external, but others can be prevented.

How do patients who have withdrawn from a study compare to those who have completed one?²

Based on a survey asking study participants about their experiences:

How well did the study meet those participants’ expectations?²

For patients who dropped out early, 6% said the study fell short of their expectations, 45% said it met their expectations and 21% said it exceeded their expectations.

For patients who completed the trial, 8% said the study fell short of their expectations, 37% said it met their expectations and 34% said it exceeded their expectations.

More than double the percentage of patients who dropped out of a study reported that it didn’t meet their expectations compared to those who completed it. More than half of patients who completed a study said it exceeded their expectations.

What are reasons to participate in a clinical research study?³

Based on a survey asking study participants about their experiences, the following were reasons to continue the study:

What motivates patients to continue participation?

When possible, try to understand why participants withdraw, and use that feedback to improve the patient experience.


  1. Beth Harper, Benchmark data from Clinical Performance Partners, Inc. and PhESi – 1998-2012
  2. http://www.medavante-prophase.com/wp-content/uploads/2018/09/2013_ciscrp_study_ineligible_participants_and_those_who_drop_out.pdf
  3. https://www.ciscrp.org/wp-content/uploads/2019/12/Participation-Experiences-04DEC-1.pdf

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