At CHDR, both the number and intensity of studies have increased in recent years, and recruiting sufficient numbers of healthy volunteers and patients can be quite a challenge, particularly given the current high standards regarding medical ethics. However, by applying novel strategies, CHDR’s Recruitment Department rises to the challenge.


  • CHDR maintains a large, up-to-date database of over 50.000 active study participants, including both healthy volunteers and patients.
  • CHDR recruits many of its specific patients through direct contact, as well as through patient organisations and physicians.
  • Next to our database, we also make use of our dedicated recruitment website,, and banner ads that link to this website.
  • Many subjects that participated in a trial return to CHDR for additional studies.
  • CHDR also reaches out to potential study participants by sponsoring public events such as sporting events and concerts. We particularly target events attended primarily by university students.

Finding healthy volunteers

As soon as the Medical Ethics Committee gives a new protocol the green light, recruiters contact potential subjects by phone and/or email. This approach is often sufficient to reach the number of subjects required to complete the study. As a basic rule of thumb, four individuals must be recruited for each subject needed in the study, as approximately half of all who reply either fail to show up for screening or fail to complete the study, and half of those who do show up for screening are ultimately excluded for medical or other reasons.

 Sometimes, when we cannot recruit enough volunteers, CHDR’s recruiters have to ‘dig deeper’, placing ads in local newspapers and posting online ads on Facebook and in the form of website banner ads. Although these channels often reach many more possible subjects, experience has taught us that these respondents often fail to show up if they have no previous experience with CHDR; therefore, these channels can have limited value. 

In the next stage of the recruitment process, volunteers who respond are contacted personally by a recruiter, who provides them with important additional information regarding the study. If the respondent is still interested, he or she is invited to CHDR for an informational meeting, where participants are given all the information they need in order to make a clear, informed decision regarding whether they wish to participate. Subjects who provide written informed consent are then invited for medical screening (in some cases, the informational meeting and medical screening can be combined in a single visit). Medical screening can also be used to teach subjects to perform specific tests, for example if the study will include CHDR’s NeuroCart® and/or PainCart®.

Finding patients

CHDR increasingly performs studies using patients with specific diseases or other medical conditions. Although recruiting patients is generally more challenging than recruiting healthy subjects, CHDR’s recruiters can usually find enough patients, thanks in part to our creative and diverse recruitment strategies. For example, recruiters maintain strong contact with various patient organisations. In the Netherlands, most patient advocacy groups are keenly interested in participating in innovative scientific research, especially given that these groups represent the end-users of that research – the patients themselves. To reach these patient groups, CHDR places advertisements in their newsletters and on their websites, and they also send alerts to specific patient groups. Ads can be placed in other media outlets as well, depending on the specific patient population needed for a study. In addition to these direct forms of recruitment, patients are often referred to CHDR by CHDR’s vast network of clinicians in a variety of fields. Together, these strategies help ensure that each study conducted at CHDR has a sufficient number of suitable patients.

MonoCentre approach 


Rather than recruiting patients for a given clinical study on an as-needed basis, Ready-for-Research establishes a pool of well-defined patient groups who are ready and willing to participate in new trials, significantly reducing recruitment time and patient screening.

With Ready-for-Research, we recruit patients who have specific medical conditions and are interested in participating in drug studies. We then screen these patients using specific protocols that have been approved by an ethics committee. With Ready-for- Research, patients are invited to our facility at CHDR. After providing written informed consent and a full medical history, patients receive a comprehensive physical examination, including blood work, and we test their performance on some of our test batteries (for example, NeuroCart®). The experience is like visiting an outpatient clinic, and we try to make the patients as comfortable as possible – after all, they are making the effort to come to us, with no tangible benefit to themselves aside from a modest payment for their time. Depending on their specific medical condition and disease stage, patients can return to CHDR on a regular basis (for example, annually or semiannually) for re-screening in order to assess their condition, general health, and other possible factors that may affect their ability to participate in an upcoming study. 


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