More than half of US clinical trials do not report data on ethnicity

The findings of more than half of US clinical trials over the past two decades did not report race or ethnicity data. In the trials that did, people from minority backgrounds were underrepresented, according to a new study by researchers from Harvard University’s Brigham and Women’s Hospital, Boston, US.

“While we found some improvement in trial diversity, minorities overall remained underrepresented relative to their US populations,” says corresponding author Brandon Turner, of the Department of Radiation Oncology. 

“Our data show that, with investments and initiatives, we can address underrepresentation in clinical trials, but these improvements have been unequal, and we need to think more broadly about why that is and what best practices should look like.”

Turner and colleagues analysed March 2000 to March 2020 trial records from, a database of privately and publicly funded clinical studies in the US. They aggregated data from trials representing more than 4.7 million people and compared race/ethnicity data to US Census population demographics. The research is published in The Lancet Regional Health – Americas. 

The team found that fewer than 44% of trials report any race or ethnicity data, but that the percentage had improved rapidly over the past few years. Among the 8871 trials that did report race or ethnicity details, the authors write, minorities (a broad term they use to encompass people of Latin American, African American, Asian and Native American populations, as defined under the US Census and Department of Health guidelines), were underrepresented, while white people were overrepresented. According to the study authors, while white people comprise 72% of the US population, they made up 80% of the people represented in clinical trials. 

Industry-funded trials appeared to have the largest gaps in minority representation.

“This is troubling because industry-funded trials often feature drugs and devices with great promise for translation to patients in the clinic,” says Turner. 

The study adds to a growing body of evidence that medical research is plagued by inherent biases that might disadvantage people from ethnic minority backgrounds. Just last year, it was reported that 95% of cell lines used in clinical research were of European descent.

Representation in clinical research matters, because there can be key genetic differences in health outcomes and disease progression between different ethnic groups. For example, people of Ashkenazi Jewish descent have a higher risk of certain genetic diseases including cystic fibrosis and breast cancer, while African American men have a higher rate of prostate cancer than men from other backgrounds.

Moreover, the clinical effectiveness and side-effect profiles of some clinically important drugs have been shown to vary between people of different ethnic backgrounds.

So, what’s representation like in Australia? According to one recent review, despite culturally and linguistically diverse Australians making up almost a third of the population, they are often excluded from clinical trials within the country. 

In fact, the Australian Clinical Trials Alliance (ACTA) is actively pushing for increased access to clinical trials for people from diverse backgrounds.

“If people are part of the Australian population, then they should have equal access to clinical trials, which will invariably result in higher quality care,” says John Zalcberg, head of the Cancer Research Program at Monash University and an ACTA board member.

“It’s important that we know, from an equity point of view, that when drugs are approved by the Australian regulator, what their role is going to be in the population more broadly,” he adds. 

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