Pragmatic Trial resources


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Participant Recruitment Strategies

Many trials face challenges with recruitment of a sufficient number of participants (McDonald 2006). Only a proportion of eligible patients will actually enter the trial. Selection occurs at the level of the health care professional and the patient. Health professionals might not invite all eligible patients to the trial. If invited, patients may decide not to participate. This may lead to slow patient recruitment and thus a longer duration of the trial. Ultimately it may also lead to a trial population that responds differently to the intervention than the targeted population, decreasing generalisability of trial results.

Specific challenges

Recruitment may be particularly challenging in pragmatic trials, as the trial is conducted in a routine care setting, where health professionals may be less experienced in, and have fewer resources dedicated to recruiting subjects to trials, as opposed to a more experienced and dedicated research setting (van Staa 2014, Donovan 2014). On the other hand, trials that are embedded in routine care, and require limited additional activities, pose fewer barriers for health care professionals and patients to participate.

Balancing increased recruitment without interfering with routine clinical practice

The response by the patients may be altered due to unintended consequences of the pre-randomization process, assessing eligibility, providing study information and signing informed consent. (McCambridge 2014, Godin 2008) This may affect generalisability, as extrapolation of the findings from the trial to future users of the drug may be limited. How much routine clinical practice is influenced by recruitment strategies and whether this indeed influences the effect estimate may vary between countries, health professionals, patient populations and disease areas.

Choice of Recruitment strategies

Specific strategies aimed at improving recruitment could help to enrol a sufficient number of patients timely (Treweek 2010). Examples of such strategies are pop-up menu’s in the electronic health record, study staff with time dedicated for informing patients about the study, modifications to the randomization process (e.g. cluster randomization or using a Zelen design), facilitating participation by reducing practical barriers, such as time and costs required to travel, arrangement of day care for children of young adults, or time schedules that do not interfere with school hours for children, and modifications to shorten the informed consent procedure. It should be noted that strategies aiming at improving recruitment could also introduce selection, if targeted at or invoking a response from a specific subpopulation. More detailed information on the pro’s and cons of recruitment strategies can be found in the paper on participant eligibility, recruitment and retention in pragmatic trials (Oude Rengerink 2017). 

Treweek and colleagues have summarized the effect on recruitment rates of strategies that have been tested in a randomized trial (Treweek 2010). However, the effect on recruitment rates and the associated costs and effects on trial duration will probably vary hugely between settings and patient populations.  We support the recommendation of the Clinical Trial Transformation Initiative working group to engage all stakeholders early in the trial development process in order to reduce barriers and improve recruitment.

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