Original article
Attrition and Retention of Ethnically Diverse Subjects in a Multicenter Randomized Controlled Research Trial

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Abstract

Recruitment and retention of subjects is critically important for the conduct of randomized clinical trials. When significant effort is given toward recruiting members of ethnic minorities in a sample, a similar rate of retention for all subgroups of subjects is essential. Little is known about why research subjects withdraw consent to participate in research and whether attrition is influenced by ethnicity or other factors. The purpose of this study was to determine the reasons for withdrawal from a large, multicenter randomized trial and whether these reasons differed among ethnic and gender subgroups. Additionally, we were interested in comparing withdrawn subjects to matched subjects who stayed in the trial to determine what factors encouraged full study completion. Using a cohort survey design, adult subjects (n = 35) who withdrew from a large, multicenter randomized trial and matched subjects who completed the study (n = 35) were interviewed by telephone after study completion. Subjects who withdrew consent tended to be female and members of ethnic minorities. The most frequent problems—reported significantly more often by subjects who withdrew consent compared to matched retained subjects—were interference with work, lack of time, complicated and cumbersome record-keeping requirements, difficult study medicine regimens, and difficulty rescheduling appointments due to lack of flexibility on the part of study personnel. Only 17% of withdrawn subjects were satisfied with the overall research experience compared to 52% of matched retained subjects. Matched subjects who completed all required visits in the randomized controlled trial reported three reasons that promoted completion: remuneration, commitment to finish, and belief that the study was important. Control Clin Trials 2001;22:236S–243S

Section snippets

Background

A major concern for the conduct of clinical trials is recruitment of subjects. Members of ethnic or racial minorities are underrepresented in most clinical trials. In the past they were not specifically recruited to participate in research studies and often declined when approached. However, generalization of research findings to the larger population requires an ethnically diverse sample. Multiple recruitment strategies and their efficacy have been discussed and debated in the literature 1, 2,

Sample

Using a descriptive survey design, subjects who were enrolled in the multicenter trial but withdrew consent to continue participation at any point after completing the run-in phase of the study were identified and interviewed. Those who were dropped by investigators because of failure to meet study criteria were not included.

In the original study [7], all eligible subjects (n = 395) were enrolled at the first visit. Of those who were enrolled, 255 subjects completed a 6-week run-in period and

Statistical Analysis

Responses to open-ended questions were subjected to thematic analysis, and themes were categorized by type of problem reported and coded. Descriptive statistics were used to analyze the frequency of responses in each category. Differences between the withdrawn and matched groups were analyzed using McNemar's chi-square test of significance with significance set at α < 0.05 and trends of interest at α < 0.10.

Results

The group of subjects who withdrew consent were slightly younger (mean age 26 ± 8.8 years), more likely to be female (60%), and members of ethnic minorities (48%) compared to the 230 subjects who completed the 16-week trial (mean age 28.37 ± 9.22 years, 55% female, 33% ethnic minorities). These differences were not statistically significant, but there was a trend (p = 0.10) toward ethnic minority subjects to be overrepresented in the withdrawn group (Figure 1).

At the beginning of the interview

Discussion

Subjects who withdraw from research studies may be more likely to have heavy work and family time demands. These subjects will require support strategies to continue participation in prospective clinical trials that require multiple visits over time. There was a trend toward overrepresentation of ethnic minorities among our withdrawn subjects. However, the reasons may be more related to socioeconomic disadvantages than minority status. Socioeconomic data were not collected in the original study

Acknowledgements

This work was supported by grant no. U10HL51845, Division of Lung Diseases, National Heart, Lung, and Blood Institute, National Institutes of Health.

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