Short communicationMinority recruitment into clinical trials: Experimental findings and practical implications
Introduction
Racial and ethnic minorities in the US suffer disproportionately from obesity and associated co-morbidities. Yet the clinical trial literature lacks sufficient attention to these populations [1]. Indeed, 86% of weight management studies between 1966 and 2003 failed to even report the race/ethnicity of recruited participants [2]. Successful “reach” to minority populations—with adequate representation in randomized clinical trials—is crucial to eliminating health disparities [3].
Research on minority recruitment for randomized clinical trials is primarily descriptive. Suggested strategies for clinical trials—which typically require a high level of participant commitment and thus pose unique recruitment challenges— include direct mail, community outreach, and mass media [4], [5]. Direct mail offers two unique advantages. First, and critical to minority engagement, direct mail can simultaneously reach different minority groups dispersed across wide geographical areas and/or living in ethnically integrated areas (i.e., contexts where in-person community outreach is less feasible), and can reach individuals without access to clinical trial gatekeepers (e.g., physicians) or to community organizations with strong in-person outreach (e.g., churches).
Second, direct mail can reach many individuals with relatively little staff time and effort [6]. Letters are typically sent to tens of thousands of individuals. Thus, even a very low response rate (due to the small proportion of recipients meeting trial-specific eligibility criteria [6]) can yield sufficient absolute numbers relative to recruitment goals [7]. Response efficiency can be improved using commercially-available, worksite, or clinic mailing lists that include key eligibility criteria such as gender or age [8]. Indeed, targeting (i.e., communications for specific audiences based on group-level characteristics) is used across consumer and health research arenas [9], [10], [11], [12], [13].
Descriptive research shows that direct mail is an effective clinical trial recruitment strategy for the general population [e.g., [14], [15]], and more effective than mass media for recruiting minorities [16], [17]. However, experimental studies are scarce [18], [19]. A recent review [20] identified only six experimental studies of direct mail recruitment strategies tested within randomized clinical trials [7], [21], [22], [23], [24], [25]; only two addressed minorities, described below [7], [21].
One direct mail characteristic tested experimentally within clinical trials is ethnically-targeted statements. While arguably “superficial,” social psychological research suggests that “surface-level” cues may affect minorities' initial trust and desire to engage [26], [27]. Corporate recruitment materials with pro-diversity statements (where ethnicity was valued) increased trust among African Americans more than “colorblind” materials (where ethnicity was immaterial) [27]. Indeed, trial recruitment letters with ethnic-specific health risk information yielded a 40% higher response rate among Latinos than letters with generic information (although not statistically significant given limited sample size, N = 561) [7]. This is consistent with evidence that effective recruitment strategies focus on recipients—their awareness of the health problem and potential impact on their own health [20]. In contrast, letters focusing on sender characteristics (e.g., same race/ethnicity as recipients) or general benefits for an ethnic group have not improved participation rates [21].
Another direct mail characteristic is personalization, e.g., addressing recipients by name [28], [29], [30], [31]. Experimental research within randomized clinical trials is sparse; two studies found an advantage [7], [32], whereas one did not [22]. However, all three compared personalized letters to shorter communications (e.g., flyers), leaving the influence of personalization unclear.
Here, we examined whether two characteristics of direct mail letters, an ethnically-targeted statement about minority health disparities and personalization, increased response rates.
Section snippets
Methods
This experiment was conducted within an 18-month randomized behavioral weight management trial [33]. In the weight management trial, women (N = 267) were recruited from Northern California communities using multiple methods, e.g., direct mail, friend/family referral, and newspaper advertisements. Women were middle-aged (48.4 ± 10.8 years old), obese (BMI = 32.1 ± 3.5), and 33.7% (n = 90) were non-White including Latina/Hispanic (10.5%, n = 28), multiethnic (≥ 2 races/ethnicities; 10.1%, n = 27), Asian (9.4%, n =
Results
In the experiment, the overall response rate was 0.7% (n = 211/30,000). Women sent letters with ethnically-targeted statements were more likely to respond than women sent letters with generic statements, 0.8% (n = 121/15,000) vs. 0.6% (n = 90/15,000), p = .03, a 34.4% increase. Women sent personalized letters were no more likely to respond than women sent non-personalized letters, p = .53. Of 211 respondents identified as minorities by the commercial firm's algorithm, 148 self-identified as minorities
Discussion
An ethnically-targeted statement in direct mail letters noting health disparities among multiple minority groups improved response rates to a weight management clinical trial. As a “surface-level” cue, the targeted statement may have suggested that ethnic identity [35] would be acknowledged in the trial setting, thereby increasing engagement [27]. Importantly, the targeted statement focused on recipients' own health rather than sender characteristics or general benefits for an ethnic group [7],
Acknowledgments
This research was supported by the Public Health Service Grants R01 CA112594 (Michaela Kiernan) and T32 HL007034 (Stanford Prevention Research Center) from the National Institutes of Health. We gratefully thank the trial participants and the research staff, and also thank Drs. Cynthia Castro, Joan Fair, Lisa Henriksen, Nancy Ellen Kiernan, and Alex McMillan for their insightful comments.
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- 1
Johns Hopkins Bloomberg School of Public Health, United States.
- 2
University of South Carolina, United States.