Racial, Ethnic Minorities Underrepresented in Clinical Trials in Macular Edema

Clinical trials involving diabetic macular edema (DME) and conducted by DRCRnet were found to have fewer participants in racial and ethnic minorities compared with the general population, according to a study published in the American Journal of Ophthalmology.¹ These racial and ethnic minorities were also found to have more severe symptoms of DME compared with other participants.

The leading cause of vision loss in patients with diabetes is DME, which affects approximately 3.8% of adults living in the US who are aged 40 years or older.² Minority groups bear the burden of DME as 38% of prevalent DME cases are in non-Hispanic Black patients who make up only 16% of all diabetes cases. The participation of racial and ethnic minorities in clinic trials has been low and those who do enroll often have worse vision outcomes. This study aimed to evaluate the disparities in racial and ethnic groups in DRCRnet clinical trials for DME, focusing on the variations in visual outcomes at baseline and differences in ocular disease characteristics.

Participants of 17 DRCRnet DME trials were pulled for this study, with all studies taking place between 2003 and 2020. All baseline data were combined from the 17 trials. The CDC Vision and Eye Health Surveillance System database was used to estimate the prevalence of DME across the country. Participants self-reported their own ethnicity and race, which were compared with the 2010 and 2020 censuses. Participants were split into the racial groups of White, Black, Asian, and other based on the self-reported data.

Racial and ethnic minorities are underrepresented in clinical trials for DME | Image credit: Miroslav110 - stock.adobe.com

Type of diabetes, insulin use, hemoglobin A1c (HbA1c), duration of diabetes, visual acuity (VA), and severity of diabetes retinopathy were measured and compared across racial groups. Ethnicity was also taken into account when using generalized linear models for the comparisons.

There were 5468 participants included in 17 trials from DRCRnet for DME, of which 75.8% were White, 16.7% were Black, 1.9% were Asian, and 1.8% were categorized as other. Non-Hispanic participants made up the majority of the participants, as well (86.3%). Both White and Black participants were over represented compared with the 2020 US Census (61.6% vs 75.8% and 12.4% vs 16.7%) whereas Asian (6% vs 3.6%), Hispanic (18.7% vs 12.5%), and other (20.0% vs 8.9%) ethnicities were underrepresented when looking at the census vs the trial representation.

The mean age of the participants at enrollment was 61 years and the mean age at diagnosis of diabetes was 44 years. The mean time between diagnosis and enrollment in the study was 17 years. Black and Asian participants were more likely to have type 2 diabetes compared with White and Hispanic participants (90.9% and 94.3% vs 87.0% and 85.2%), though most type 1 diabetes reports were from White participants. The use of insulin was lower in Asian (44.0%), Hispanic (55.5%), and other (56.8%) races compared with Black (64.1%) and White (63.7%) participants.

Proliferative diabetic retinopathy was more prevalent in Asian (20%), Hispanic (22.9%), and other (27.1%) participants when compared with White (18.7%) and Black (14.8%) participants. Female participants, diagnosis at an older age, Hispanic ethnicity, and more severe diabetic retinopathy were all factors that were associated with worse visual acuity in the eye included in the study.

There were some limitations to the study. The DRCRnet trials are primarily government funded and did not take into account trials funded by the industry. The trial data were from multiple years between 2003 and 2020 whereas the census data were only from 2 years and the prevalence of DME was only from 2019, which could skew the accuracy of the data. The “other” ethnicity combined American Indian/Alaskan Native, Native Hawaiian/Pacific Islander, and biracial, which could affect the analysis of this subgroup.

The researchers concluded that some minority groups were underrepresented in clinical trials regarding DME that were conducted by DRCRnet, but also that these minorities presented with more severe diabetes and diabetic eye disease compared with other racial and ethnic groups. “Our findings further highlight the ongoing need for diverse recruitment of participants in DME clinical trials,” the authors wrote.

References

1. Li M, He J, VanderBeek BL, Ying G. Racial and ethnic disparities at enrollment in DRCRnet clinical trials for diabetic macular edema. Am J Ophthalmol. Published online February 26, 2025. doi:10.1016/j.ajo.2025.02.029
2. Varma R, Bressler NM, Doan QV, et al. Prevalence of and risk factors for diabetic macular edema in the United States. JAMA Ophthalmol. 2014;132(11):1334-1340. doi:10.1001/jamaophthalmol.2014.2854