Glossary
Enrollment rate
How fast a trial or site enrolls participants, usually expressed as patients enrolled per site per month and compared with the rate the plan assumed.
What does Enrollment rate mean in clinical research?
ClinicalTrials.gov regulations define enrollment as the estimated (target) or actual total number of human subjects enrolled in a clinical trial.[1] Enrollment rate adds time and site count to that number, so studies of different sizes can be compared. In the CREST-2 stroke prevention trial, for example, the recruitment rate was 0.26 patients per site per month.[2]
Low rates are why so many studies miss their timelines. A 2018 review cited a study of 114 UK trials in which only 31% met their enrollment goals, and another analysis in which one-third of publicly funded trials required a time extension because they failed to meet initial recruitment goals.[3]
Practical note: track the rate by stage, not only the final count. Patients identified, contacted, pre-screened, consented and randomized each month show whether the constraint is finding patients, reaching them or converting them. Bond's dashboard reports each of those stages, and Engage adds outreach capacity when reaching patients is the bottleneck.
Sources
- 1.42 CFR 11.10 Definitions (Clinical Trials Registration and Results Information Submission) · eCFR (NIH/NLM), 2026
- 2.Factors Associated With Time to Site Activation, Randomization, and Enrollment Performance in a Stroke Prevention Trial · Stroke (American Heart Association), via PubMed, 2017Quote: "The recruitment rate was 0.26 (95% confidence interval, 0.23-0.28) patients per site per month."
- 3.Factors associated with clinical trials that fail and opportunities for improving the likelihood of success: A review · Contemporary Clinical Trials Communications, via PMC, 2018Quote: "A study of 114 trials in the UK indicated that only 31% met enrollment goals." Also: "In addition, Campbell et al. reported that one-third of publicly funded trials required a time extension because they failed to meet initial recruitment goals."