With almost a half century of experience in clinical trials, the VA Cooperative Studies Program is in a position to inform the research and policy community about enrollment of patients in randomized controlled trials according to the participant’s race and ethnicity. This is important because of the ongoing national debate concerning potential bias in enrollment procedures for these important and often definitive clinical trials. Should any one group of patients be excluded for trials defining the importance of therapeutic interventions, clinicians may be reluctant to generalize the findings of these studies to groups who may be excluded. Thus, failure to enroll a representative sample of patients may enhance disparities in access and utilization of important interventions.
We will focus this study on the participation in controlled trials by the three most prevalent racial and ethnic groups: White, Black and Hispanic. While Native Americans and Pacific Islanders, among other important racial and ethnic groups, are also represented in the veteran population, their overall numbers are too small to allow valid statistical inferences. We are particularly interested in trial-related characteristics -- e.g., the types of trials -- that are associated with participation rates by minorities as these factors may suggest interventions to improve the situation. Specific Aims: 1) describe the experience of VA Cooperative Studies Program trials in enrolling White, Black, and Hispanic patients over time; and 2) determine if minority enrollment is modified by type of intervention: invasive or non-invasive.
We are performing a secondary analysis of randomized controlled trial administrative data pertaining to all completed trials within the VA Cooperative Studies Program between 1976 and 2000. The data of primary interest pertain to rates of enrollment among eligible patients. We will supplement these data with information obtained from VA administrative files (Patient Treatment File) relating to the racial/ethnic distribution of the population of patients at each VA facility (i.e., those that participated in a given trial) during the patient recruitment phase of the specific trial. By this approach, we will have a reasonable (and defensible) approximation of the likely denominator of veterans potentially eligible for these studies according to their race and ethnicity.
138 VA CSP clinical trials were initiated between 1975 and 2000, 83 contained information on race for 71,463 patients. Based on unique standardized enrollment ratios, 60 of the 83 trials had 95% confidence intervals that excluded 1.0. Of these, 32 studies enrolled more White patients than expected and 28 enrolled more Black and/or Hispanic patients than expected based on the racial distribution of patients hospitalized at sites involved in the trials. When trials were separated by intervention type, 13 of the 19 trials that had an invasive arm enrolled fewer minority patients than expected. In trials that targeted diseases for which minority race was a risk factor (diabetes, hypertension and end stage renal disease), 11 of the 14 trials enrolled more minority patients than expected.
To date, the largest study that addressed the racial composition of patients enrolled in clinical trials examined 10 studies in the area of stroke risk reduction. Thus, federal policy surrounding this issue is currently based on a general perception of low enrollment of under-represented minorities in research without a clear understanding of the nature of the problem. Moreover, previous research in this field is confounded by the socio-economic status of the enrolled population. Because the majority of traditional clinical trials are conducted within academic medical centers, financial barriers to care for under-represented minorities may also explain the low proportion of these patients in clinical trials. Thus, the VA is in a position to make a major contribution to this line of research because once patients are enrolled in the system, financial matters should have minimal influence on their access to care or research protocols, thereby reducing or eliminating this variable as a potential confounder.
- Oddone EZ, Olsen MK, Lindquist JH, Orr M, Horner R, Reda D, Lavori P, Johnson G, Collins J, Feussner JR. Enrollment in clinical trials according to patients race: experience from the VA Cooperative Studies Program (1975-2000). Controlled clinical trials. 2004 Aug 1; 25(4):378-87.