Site enrollment rate, outcomes, and study drug effects in a multicenter trial. Results from RELAX-AHF

Background: Site selection is critical in acute heart failure trials. We assessed whether the enrollment rate per site affects patients' characteristics, outcomes and treatment response. Methods and results: A total of 1161 patients enrolled at 96 sites in the RELAX-AHF trial (serelaxin vs placebo) were included. Annualized enrollment rate was calculated as the total number of patients enrolled at each site divided by time that the site was open (patients per year). Sites were classified in low (20 patients per site/year) and were compared for prognosis and serelaxin effect. High enrolling sites were more prevalent in Eastern Europe and Israel. Time from hospital admission to randomization was shorter in high enrolling sites (6.3 +/- 4.4 h >20 patients sites versus 8.7 +/- 4.5 h for