Background/Aims
Diverse samples in clinical trials can make findings more generalizable. We sought to characterize the prevalence of clinical trials in the United States that required English fluency for participants to enroll in the trial.
Methods
We randomly chose over 10,000 clinical trial protocols registered with ClinicalTrials.gov and examined the inclusion and exclusion criteria of the trials. We compared the relationship of clinical trial characteristics with English fluency inclusion requirements. We merged the ClinicalTrials.gov data with U.S. Census and American Community Survey data to investigate the association of English language restrictions with ZIP-code level demographic characteristics of participating institutions. We used Chi-squared tests, t-tests, and logistic regression models for analyses.
Results
English fluency requirements have been increasing over time, from 1.7% of trials having such requirements before 2000 to 9.0% after 2010 (p<0.001 from Chi-squared test). Industry sponsored trials had low rates of English fluency requirements (1.8%) while behavioral trials had high rates (28.4%). Trials opening in the Northeast of the U.S. had the highest regional English requirement rates (10.7%) while trials opening in more than one region had the lowest (3.3%, p<0.001). Since 1995, trials opening in ZIP-codes with larger Hispanic populations were less likely to have English fluency requirements (OR=0.92 for each 10 percent increase in proportion of Hispanics, 95% CI 0.86–0.98, p=0.013). Trials opening in ZIP-codes with more residents self-identifying as Black/African American (OR=1.87, 95% CI 1.36–2.58, p<0.001 for restricted cubic spline term) or Asian (OR=1.16 for linear term, 95% CI 1.07–1.25, p<0.001) were more likely to have English fluency requirements. ZIP-codes with higher poverty rates had trials with more English language restrictions (OR=1.06 for a 10 percent poverty rate increase, 95% CI 1.001–1.11, p=0.045). There was a statistically significant interaction between year and intervention type, such that the increase in English fluency requirements was more common for some interventions than for others.
Conclusions
The proportion of clinical trials registered with ClinicalTrials.gov that have English fluency requirements for study inclusion has been increasing over time. English language restrictions are associated with a number of characteristics, including the demographic characteristics of communities in which the sponsoring institutions are located.