A new analysis of cardiovascular clinical trials reveals significant enrollment challenges in the United States, despite the country maintaining the highest number of trial sites globally. The study, led by Muhammad Shahzeb Khan, MD, MSc, and Javed Butler, MD, MPH, from Baylor Scott and White Research Institute, examined 51 major cardiovascular trials published in leading medical journals between 2019 and April 2024.
US Trial Sites Show Lower Enrollment Efficiency
The analysis revealed striking disparities in enrollment efficiency across regions. While the United States contributed 1,133 sites (25.8% of total), these sites enrolled only 19.9% of all participants, resulting in the lowest patient-per-site ratio of 15.6 patients. More concerning is the monthly enrollment rate of 0.2 patients per site, significantly lower than other regions.
Global Enrollment Patterns
The study, which analyzed data across 70 countries involving 292,985 patients, demonstrated notable regional variations:
- North America reported 1,377 sites (31.4%) but achieved the lowest patient-per-site ratio of 17.3
- South America, despite having only 329 sites (7.5%), achieved the highest patient-per-site ratio of 24.8
- Eastern European trials demonstrated strong performance with a median per-site ratio of 16.0 patients
Trial Scale and Complexity
The analyzed trials showed considerable variation in size and scope:
- Median of 320 sites per trial
- Average enrollment of 4,786 participants
- Typical enrollment period of 32 months
- Patient-per-site metrics ranging from 3.8 to 131.9
- Nearly one-third of trials required more than 500 sites
Implications and Future Directions
"Trial evidence must reflect diverse populations to ensure treatments are relevant to all," emphasized the research team. The findings suggest underlying challenges in the US clinical trial infrastructure, including legal, regulatory, and cost-related barriers.
The researchers propose several potential solutions:
- Implementation of decentralized trials
- Combination of remote and in-person participation options
- Enhanced clinical trial infrastructure
- Improved strategies to address enrollment disparities
These findings are particularly significant given cardiovascular disease's high prevalence in the United States. The low enrollment rates not only impact resource utilization but also potentially delay critical treatments reaching patients who need them.
