Language requirements for enrollment in randomized controlled trials (RCTs) are rarely stated; however, due to intersectionality of language, race, and ethnicity, assessing language stipulations in trials on diseases disproportionally affect racially and ethnically diverse individuals is needed. We investigated language requirement frequency, eligibility criteria readability, and race and ethnicity reporting from RCTs in high-impact publications and public database ClinicalTrials.gov. This cohort study included 35 RCTs and 42723 participants from systematic searches in MEDLINE, Scopus, EBSCO, Web of Science Core Collection, World Health Organization COVID-19 database April 2017-December 2025. We included drug RCTs on heart disease, stroke, cancer, respiratory disease, diabetes, and COVID-19, on ClinicalTrials.gov and published with ≥75% US participants. We assessed language requirements frequency in eligibility criteria in publications, protocols, informed consent forms, and ClinicalTrials.gov, and readability of consent forms and eligibility criteria in protocols and ClinicalTrials.gov according to funder and disease. We report 58% of industry-funded RCTs lack mention of languages in eligibility criteria or trial documentation. The median (IQR) readability of eligibility criteria assessed with Flesch-Kincaid Grade (FKG), Gunning Fog (GF), and Simplified Measure of Gobbledygook (SMOG) is higher than the recommended eighth-grade level in protocols with FKG = 12.7 (11.0-13.9), GF = 14.5 (12.4-15.4), and SMOG = 13.7 (12.1–14.4) and ClinicalTrials.gov with FKG = 12.9 (10.8-13.9), GF = 14.0 (12.2–15.3), and SMOG = 13.9 (12.2–15.6). Informed consent forms also have reading grade levels higher than recommended for the general public, with FKG = 8.2 (7.3–9.3), GF = 9.3 (8.8-10.8), and SMOG = 10.8 (10.2-11.8). Involving stakeholders during RCT design is needed to encourage explicit language reporting and high readability, which could be instrumental in RCT accessibility and equity. Doctors determine the best treatments for people from research that includes clinical trials. Regardless of language, everyone should have a chance to participate. We assessed clinical trial eligibility criteria in a public trial registry, protocols, consent forms, and scientific articles to determine required participant languages, readability of eligibility criteria, and whether participants’ race information was fully described. There is overlap between race, ethnicity, and English language proficiency. Trials studying diseases that burden underrepresented groups—American Indian or Alaska Native, Black, Asian, Native Hawaiian or Pacific Islander, Middle Eastern, and Latinx—often provided information that was difficult to read and did not state what language was required. Clinical researchers could provide essential trial information to potential participants in an easy-to-read format. Pranic et al. perform a systematic analysis of clinical trials to examine language requirements and overall readability by target populations. They find that trials often present information that is difficult to read, and do not specify the language required of participants.
Pranić et al. (Fri,) studied this question.