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Recruitment of Older Kidney Transplant Recipients to a Longitudinal Study

O’Brien, Tara; Russell, Cynthia L.; AlKahlout, Noor; Rosenthal, Anna; Meyer, Tess; Tan, Alai; Daloul, Reem; Hathaway, Donna

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doi: 10.1097/NNR.0000000000000406
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Despite the growing number of older adults in the United States (Cherubini & Gasperini, 2017), efforts to recruit them for longitudinal studies often remain challenging. Older adults face many challenges preventing them from enrolling into a longitudinal study, for example, frailty, limited mobility, and poor cognition (Sanders et al., 2018). Other barriers that prevent older adults from enrolling in research studies include inability to drive to the research site (Sun, Gilbert, Ciampi, & Basso, 2017), vision and hearing impairment (Trujillo Tanner et al., 2018), distrust of researchers, (Hart et al., 2017), and not understanding the study protocol (Prusaczyk, Cherney, Carpenter, & DuBois, 2017).

Other common reasons for failure of researchers to recruit older adults are insufficient planning, lack of research staff, and overly hopeful expectations (Luepker, 2018). Moreover, the type of research intervention can impact the desire to participate in research. For example, lifestyle intervention studies that involve walking may be impacted by barriers to exercise such as lack of mobility and pain with walking (Sanders et al., 2018). Additionally, researchers implementing strict inclusion and exclusion criteria in a population that suffers from multiple chronic diseases may impact study enrollment as well (Caldieraro-Bentley, Kelechi, Treat-Jacobson, & Mueller, 2018).

The National Institutes of Health reported that 80% of clinical trials fail to meet timelines due to delays in participant recruitment (Pinto et al., 2017). Such slow recruitment could lead to a delay in testing the intervention for effectiveness or outcome results, ultimately impeding the development of science (Barber, Bardach, & Jicha, 2018). Thus, it is critical to enhance the recruitment of underrepresented populations with chronic disease to ensure the rigor required for generalizability, trustworthiness, and inference of results. These efforts will subsequently contribute to healthcare improvement for these individuals (Weil, Mendoza, & McGavin, 2017).

Successful recruitment of older adults often requires a multifaceted approach incorporating multiple strategies, perhaps because of their lifetime experiences and skill set for interacting with others. Recently, the National Institute of Aging (NIA) developed a toolkit to aid in the recruitment of older adults for research studies (NIA, 2016). The NIA’s toolkit provides information on how to spread the message about research participation through printed materials, technology approaches, and in-person recruitment techniques (NIA, 2016). Today, many research teams rapidly utilize technology recruitment strategies (Graham et al., 2012; Jones, Goldsmith, Hewson, & Williams, 2013; Nash et al., 2017). However, limited information is available for the outcome of using technology recruitment strategies among older adults with chronic disease (Juraschek et al., 2018). One group particularly well suited for inquiry to evaluate multiple recruitment strategies is older kidney transplant recipients (KTRs). Older KTRs have a high prevalence of chronic diseases (obesity, cancer, and cardiovascular diseases) that predispose them to cognitive impairment and frailty (Pinter et al., 2017). Such characteristics make it challenging to recruit them to enroll in a research study. Currently, in the United States, there are 150,549 KTRs between the age of 50 and 64 years and 52,805 KTRs in 65 years and older (Health Resources and Services Administration, U.S. Department of Health & Human Services, 2019). Our study explored the rates and cost of five different methods used for recruiting post-KTRs over the age of 60 years for a 1-year pilot longitudinal physical activity interventional study, with the aim of increasing daily steps. The framework of the interventional clinical study examined the concept of merging an activity tracker with SystemCHANGE to increase physical activity in older KTRs (O'Brien, Hathaway, Russell, & Moore, 2017). The inclusion criteria for the study were (a) age of 60 years or older, (b) ability to speak English, (c) greater than 3 months posttransplant, and (d) ownership of a smartphone. Participants were excluded if they used assistive walking devices.


We recruited the sample from January through September 2018 from a Midwest Transplant Program. At the time of this study, the transplant center performed more than 6,825 kidney transplants at age 50–64 years and 2,041 kidney transplants at age 65 years and older. On average, the clinic scheduled 30 post-kidney transplant appointments per week for patients aged 60 years and older. Our goal was to recruit a convenience sample of 60 years and older post-KTRs who owned a smartphone capable of accessing mobile activity tracker data. After institutional review board approval was obtained, we used a feasibility design (Bowen et al., 2009) to explore the following recruitment methods to enroll an older population with chronic disease: (a) face-to-face contact in the transplant clinic, (b) paper flyers placed in the transplant clinic, (c) Facebook, (d) an online newsletter for KTRs who were enrolled as volunteers for a local organ and procurement organization associated with the transplant clinic, and (e) a university website listing of research studies. Written informed consent was obtained from each participant enrolled into the study.

Recruitment Strategies

Face-to-Face Contact

The healthcare providers in the transplant clinic providing care to the KTRs informed possible participants about the study during their clinic appointment. If the participant expressed interest, the healthcare provider would then inform the research assistant (RA). Three different RAs were trained to recruit participants to enroll in the study. All RAs used the same written checklist to explain the study, answer questions, and solicit consent to participate in the study.

Paper Flyers

We developed paper flyers using bright colors and large font. The flyers contained a brief description of the study, inclusion and exclusion criteria, and the principal investigator’s (PI) contact information. The flyers were strategically placed in the transplant clinic behind each patient room door. The thought was that patients would be more likely to view and read the flyers while they waited for their appointment.


A Facebook platform was developed in collaboration with the research team and the university’s Clinical and Translation Science Center. The Facebook site was made available to the public on the Facebook platform. The site provided a brief description of the study, inclusion and exclusion criteria, and the PI’s contact information.

Online Newsletter

KTRs who were enrolled as volunteers for a local organ and procurement organization associated with the transplant clinic were e-mailed a monthly newsletter via the organization’s listserv. The newsletter provided a brief description of the study, inclusion and exclusion criteria, and the PI’s contact information.

University Website

The university website, called Study Search, provided study exposure by providing a brief description of the study, inclusion and exclusion criteria, and the PI’s contact information. The university website provides a list of all institutional review board-approved research studies at the hospital and university that are seeking volunteers to enroll.

Data Analysis

Descriptive statistics were used to summarize the method of enrollment, and chi-square statistics were used to explore the differences for gender and race of enrollment.



The sample consisted of 60 participants with a mean age of 64.9 years, SD = 4.7 years. Most of the study participants were men (n = 39, 65%) of whom 24 (61%) were White and 15 (39%) were Black. Of the 21 (35%) women participants, 12 (57%) were White, 6 (28.5%) were Black, 2 (9.5%) were Asian, and 1 (5%) was Middle Eastern.


Enrollment spanned 9 months and included face-to-face contact in the transplant clinic, paper flyers placed in the transplant clinic, a Facebook platform, an online transplant newsletter, and a university website seeking volunteers using a listing of research studies available to the public. Of the 424 patients approached by the same RA using a written script in the transplant clinic, n = 12 (8%) did not own a smartphone. We e-mailed the transplant newsletters once a month for 9 months to 142 KTRs, 469 people viewed the Facebook platform, and 69 people viewed the university website. Among the participants who enrolled in the study, the largest number (75%, n = 45) emerged using the face-to-face method in the transplant clinic. The online transplant newsletter was the second-best recruitment source (18%, n = 11). Paper flyers yielded (7%, n = 4) enrollment. Facebook and the university study search site generated no recruitment among this population (Table 1). We found no difference between genders (χ2 = 2, 1.92, p = .38) or race (χ2 = 6, 8.92, p = .18) in regard to the method of enrollment. The cost of each strategy varied. The RA recruited participants for 9 months in the clinic using the face-to-face method for 20 hours per week for 26 weeks, for a total cost of $7,888.00. The total cost to print paper recruitment flyers was $37.00, whereas the online newsletter, Facebook portal, and the university study search site had no charges.

Recruitment Methods, Exposure Methods, and Total Number of Participants Recruited to Enroll Older Kidney Transplant Recipients for a Longitudinal Physical Activity Study


Previous studies have found that technology recruitment strategies have the potential to reach large numbers of people (Staffileno et al., 2017). Our study suggests, however, that technology recruitment strategies for older KTRs may not be as effective. Even though our sample had a high ownership of smartphones, recruitment strategies using face-to-face and online newsletter associated with the transplant clinic organization appeared to be more effective than strategies not associated with the transplant clinic (Facebook and a university website). Our findings may imply that using a familiar organization communication method to recruit older populations with chronic diseases may be the most beneficial. A recent systematic review found similar results in which there was no strong evidence that any single recruitment strategy was more effective for recruiting individuals to research studies. Using a dedicated person for face-to-face recruiting, however, was more promising for conducting effective recruitment (Preston et al., 2016).

Another question is how to attract potential participants to electronic recruitment sources such as Facebook and the university website. A common recruitment practice used by many marketing companies is to use many different sources to cast a broad net to find potential participants (Dobrow, 2017). However, these same companies caution against using a single source for recruitment, as this practice may result in increased time and costs (Recruitment Process Outsourcing Association, 2015). In this particular study, 9 months were needed to recruit adults 60 years and older from a large transplant center using multiple methods of recruitment. Thus, the results from our study imply that a face-to-face recruitment strategy is clearly more effective with a chronic disease population and should be used as the cornerstone of a multifaceted approach for recruitment.

One limitation of our study was the sample being composed predominantly of White men; however, our demographics are similar to the entire U.S. population of older KTRs (Health Resources and Services Administration, U.S. Department of Health & Human Services, 2018). Another limitation was the inability to know how many KTRs viewed the flyer or online transplant newsletter. Moreover, we were unaware of how many viewers of the Facebook portal and university website were actual KTRs. In addition, we could not ascertain how many individuals were exposed to multiple recruitment approaches before they were enrolled into the study by the RA using the face-to-face method. Despite these limitations, the findings provided insight for considerations of using multiple recruitment strategies when recruiting older adults with chronic disease.


Our study findings reveal important implications for researchers to consider when designing future studies, particularly related to budget planning and study timelines for recruitment. Though technology-based recruitment strategies may be inexpensive and have the potential of reaching a large number of older adults with chronic disease, if used alone they are unlikely to yield the desired sample size, particularly in an older population. Face-to-face encounters where individuals receive care appear to be the greatest recruitment source, which is likely enhanced by institutional-based electronic platforms. A consideration for future research is to survey the participants who enroll in the study to ascertain the specific types of recruitment approach they were exposed to during the recruitment process. These data are important for matching particular recruitment approaches to participants with certain characteristics (e.g., age, gender, race/ethnicity). Thus, future research should expand and confirm the evidence suggested by this exploratory study to identify the most efficacious way to attract older adults with chronic disease to enroll in research studies using multiple recruitment strategies.


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kidney transplantation; patient selection; recruitment strategies; research

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