Patient- and trial-specific barriers to participation in cardiovascular randomized clinical trials

The purpose of this study was to quantitatively examine the association of patient- and trial-specific factors with participation in cardiovascular randomized clinical trials.

Randomized clinical trials are central to evidenced-based medicine, but low patient participation rates and potentially modifiable barriers are not well understood.

At a large U.S. academic health system, we examined screening logs from December 1, 2005, to February 28, 2011, from 15 cardiovascular randomized clinical trials. We identified 655 patients who were screened and potentially eligible for participation in at least 1 trial. We used multivariable Poisson regression to quantify the risk of not participating in a trial associated with patient- and trial-specific factors.

The median age was 63 years (interquartile range: 54 to 72), 35% were women, and the median Charlson Index was 2 (interquartile range: 1 to 5). Forty-two percent of patients did not participate in a trial. In multivariable regression (C-Index 0.85), trial-specific factors strongly associated with not participating included intensive trial-related testing (relative risk [RR]: 1.89; 95% confidence interval [CI]: 1.63 to 2.20) and anticipated trial participation >6 months (RR: 4.10; 95% CI: 2.30 to 7.29). Patient-specific factors associated with not participating included older age (RR: 1.23; 95% CI: 1.11 to 1.36, per 10-year increase if age ≥65 years), out-of-state residence (RR: 1.26; 95% CI: 1.04 to 1.54), and female sex (RR: 1.17; 95% CI: 1.01 to 1.35). Race was not associated with participation.

While patient-specific factors were associated with not participating in cardiovascular trials, longer trial duration and intensive trial-related testing were most strongly associated with risk for patients not participating. Innovative trial designs fostering convenience may most enhance trial participation.