Trial Participant Retention

Retaining Trial Participants: Adherence and Dropout Mitigation

Patient participation is essential to clinical trial success. It is also one of the most challenging parts of running a successful trial.


The problem starts at enrollment: Studies of clinical trial recruitment and retention indicate that only 20 to 30 percent of clinical trials meet enrollment goals, writes David B. Fogel. Then many clinical trial studies struggle to keep the patients that are enrolled engaged.

To retain patients, clinical trial teams need to understand why patients drop out. They must also identify the most likely dropout triggers in each study and choose tools that address those issues.

The Problem of Patient Retention

According to Caroline Jackson, executive vice president of patient services at mdgroup, patients drop out of clinical trials for four main reasons:

  • Issues that make participation inconvenient or overwhelming.
  • Lack of communication from clinical trial teams and other resources.
  • A sense of being underappreciated or unrecognized as an individual human participant.
  • Financial barriers.

“To resolve the most common issues facing patient retention, we need a shift towards patient-focused protocols,” says Jackson.

Yet clinical trials as a whole have shifted away from patient-friendly approaches. In recent years, clinical trial durations have increased by 70 percent, the number of trial protocol procedures has increased by 65 percent, and the size of case report forms has more than doubled, writes Walter Alexander in an article in Pharmacy and Therapeutics. Even consent forms became longer and more complex.

Time is a major concern for many clinical trial participants. In a 2022 study, Katherine A. Collins and fellow researchers examined the reasons that patients dropped out of exercise interventions targeting excess weight and prediabetes. They found that two-thirds of patients who dropped out (67 percent) did so before beginning or while ramping up exercise interventions. Forty percent claimed they dropped out because they did not have time to exercise. However, none of the patients who completed the ramp-up period, dropped out within the next six to eight months of training.

Problem of Patient Retention

Maintaining Adherence in Clinical Trials

Patients no longer passively accept medical care and advice. Today, digital connectivity places information about patients’ conditions and treatments at their fingertips. The internet also provides widespread access to patient support and advocacy groups, where patients can share information — including their personal experiences in clinical trials.

Building adherence in clinical trials must account for patient access to information and support groups. Adherence efforts must also acknowledge that with greater access to information and support groups comes greater exposure to potentially unhelpful elements, including misinformation and complaints from fellow patients.

In a meta-ethnographic study published in BMJ, Zoe C. Skea, Rumana Newlands, and Katie Gillies examined a total of 168 patients who dropped out of various clinical trials. The researchers found that these patients shared common concerns that the trial was a poor fit for them personally.

Specifically, patients identified lack of “fit” in areas such as:

  • Their health and whether they could participate in the trial.
  • Their preferred ways to receive care during the trial.
  • Their beliefs or experiences relating to clinical trial medications.
  • Their concerns about integrating trial participation into their existing schedules.

For these patients, the decision to stay in the trial or drop out rested on individual factors. Patients were concerned about their ability to participate comfortably in the trial, rather than about the trial itself.

One way to improve adherence in clinical trials is to address patients on an individual level. A study by Jingjing Shang and fellow researchers sought to understand why cancer patients adhered to or dropped out of a clinical trial focused on the effects of exercise during cancer treatment. The researchers began the study by categorizing participants according to factors that could affect their adherence, like baseline fitness, fatigue levels, treatment-related mood issues, and marital status.

By categorizing patients according to the factors that made them more or less likely to drop out, the researchers were better able to understand how those factors interacted with adherence and also to address concerns as they arose. The researchers recommended that future exercise clinical trials use similar pre-treatment variables to better understand adherence and dropout factors.

Another way to tailor studies to boost adherence is to offer personalized rewards for patients’ completion of certain tasks. For example, in a 2020 study, Zarqa Ali and fellow researchers rewarded patients in an atopic dermatitis study by providing personalized genetic reports to participants as they completed key trial tasks. Ninety-six percent of the participants completed the study, finishing more than 90 percent of all study tasks. Most participants said they would participate in a second study or would have adhered to a longer study.

Patients approach clinical trials as individuals. Their needs and concerns are contextual and situated within their individual experiences. By understanding patients’ pre-treatment history and needs, their schedules and obligations, and their desires for recognition, clinical trial teams can build patient-centric approaches into their work — without unduly burdening themselves.

Adherence in Clinical Trials

How to Identify and Address Dropout Risks in a Trial

To understand why patients drop out of specific clinical trials, trial teams must first define and measure dropout and retention metrics.

In a 2020 study in Multiple Sclerosis and Related Disorders, Rachel Dennett, et al. sought to understand why patients drop out of controlled trials that examine the effect of exercise on MS symptoms.

After reading 93 articles reporting on 81 studies, however, the researchers discovered they could come to no conclusions regarding their original inquiry. Lack of consistency in defining adherence measurements obfuscated the information available, and many trials failed to track adherence or dropout rates at all.

“Researchers should ensure clear transparent measurement and reporting of adherence and drop-out data in future trials,” Dennett and the research team recommend. Building data sets is the first step toward better understanding and addressing dropout risks in particular trial settings.

Time and fit remain concerns for both clinical trial patients and clinical trial teams. “To improve retention in clinical trials, researchers should work to reduce the burden on trial participants both through the design of the intervention itself as well as through simplified data collection processes,” write Skea, Newlands and Gillies.

Using streamlined clinical trial management platforms is one way to identify and address potential burdens on clinical trial participants, as well as to reduce the overall burden on clinical trial teams. Platforms can organize trial data more easily. The tools allow clinical trial teams to identify pre-treatment factors that could affect patient adherence. They also allow researchers to identify potential options for personalized rewards to further boost patient adherence to specific tasks.

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