Study finds geographic and institutional disparities for DR and DME clinical trials

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A study analyzed the geographic and institutional disparities in clinical trial distribution for candidates targeting the treatment of diabetic macular edema (DME) and diabetic retinopathy (DR) within the United States. The results found that there are unequal distributions of these clinical trials among rural and low-income populations.

Methods

• The trial assessed Phase 2 through Phase 4 trials for both DME and DR with more than 50 patients that were initiated between January 1, 2000, and December 31, 2023.
• The data for these trials was obtained from Clinicaltrials.gov, and multicenter trials were excluded from the geographic analysis citing the missing site-specific enrolment data.
• Regional categories were South, Midwest, West, and Northeast according to the US Census Bureau regional definitions.
• Institutions were categorized as academic, public, or private.
• Proportions with 95% confidence intervals (CIs) assessed trial distribution, while odds ratios (ORs) and relative risk (RR) compared institutional affiliations between diseases.
• Multinomial logistic regression evaluated predictors of institutional affiliation.
• P-values assessed significance for categorical comparisons; statistical analysis was conducted in SPSS (version 29, IBM, Chicago, IL).
• This study protocol was exempt from institutional review board approval by the Albert Einstein College of Medicine due to the use of public, de-identified data, following STROBE guidelines.¹

Results

In accordance with the methods above, a total of 83 DR and 43 DME trials were included.¹

Among DR trials, 32.5% (95% CI, 22.5%–42.6%) reported geographic sites, compared to 6.9% (2.3%–12.6%) of DME trials (P<.001).¹

DR trials were mainly private (45.8%, 95% CI: 35.1%–56.5%), followed by public (33.7%, 23.6%–43.9%) and academic institutions (15.7%, 8.1%–23.3%). DME trials were mostly public (58.1%, 43.4%–72.9%), followed by private (34.9%, 21.0%–48.7%) and academic institutions (7.0%, 2.0%–12.0%).¹

The researchers found that the geographic distribution of DR and DME trials was unequal across regions (P<.001). DR trials were concentrated in the South at 37.0% (18.8%–55.3%) and Midwest at 37.0% (18.8%–55.3%), with fewer clinical trial sites located in the West (14.8%, 1.4%–28.2%) and Northeast (11.1%, 5.81%–19.34%). DME trials occurred in the South (75.0%, 50.2%–99.8%) and West (25.0%, 5.1%–44.9%), with no trials in the Midwest or Northeast, a notable reporting.¹

DR trials were more likely to be privately sponsored (OR: 4.193, 95% CI: 1.609–10.924) than DME trials, and disease type predicted institutional affiliation (P = 0.011) on multinomial logistic regression.¹

The study broke down this data into 2 tables, which are available online.

Analysis

From this data, the researchers noted several conclusions and identified areas of disparity. Importantly, they explained that by excluding multicenter trials due to the unavailable location-specific data in these trials, there may be misrepresentation of geographic diversity when enrolment is disproportionately concentrated at select locations. They cited that previous studies have shown discrepancies in reporting location-specific data despite data verification, complicating geographic assessment.²

The researchers found that DR trials were significantly more likely to be privately sponsored, while DME trials were led primarily by public institutions. This implies funding-driven biases. In addition, limited academic involvement in DR and DME trials shows underrepresentation of non-commercial research, consistent with studies showing limited industry-funding to academic centers.¹

DME trials were disproportionately located in the Southern US, with no trials located in the Northeast or Midwest, showing clear gaps in regional access. Social determinants of health, such as socioeconomic status and geographic access, may also influence diabetic retinopathy management and contribute to trial access disparities.¹

The researchers suggested that policies should promote equitable geographic trial distributions and enhance academic engagement to ensure balanced representation.¹

References:

1. Shah, J., Pathuri, S., Zheng, J. et al. Assessing geographic and institutional disparities in United States diabetic eye disease clinical trials (2000–2023). Eye (2025). https://doi.org/10.1038/s41433-025-03791-5

2. Andersen JR, Byrjalsen I, Bihlet A, Kalakou F, Hoeck HC, Hansen G, et al. Impact of source data verification on data quality in clinical trials: an empirical post hoc analysis of three phase 3 randomized clinical trials. Br J Clin Pharm. 2015;79:660–8. https://doi.org/10.1111/bcp.12531.