Clinical Trial Enrollment Duration
Estimate how long enrollment will take by combining the target sample size with active sites, per-site enrollment rate, screen failure, and startup delay assumptions.
Planning tool only. Align enrollment assumptions with protocol amendments, regulatory feedback, and operational feasibility reviews.
Examples
- 360 patients, 24 sites, 0.80 enrollments per site per month, 15% screen failure, 1 month startup ⇒ 23.06 months at 16.32 patients/month.
- 120 patients, 10 sites, 0.50 enrollments per site per month, screen failure blank, startup blank ⇒ 24.00 months at 5.00 patients/month.
FAQ
Should I include patients who fail screening in the target?
No. The target enrollment is the number of eligible, randomized, or treated patients required by the protocol. Screen failures should be reflected in the screen failure percentage instead.
How do I estimate the per-site enrollment rate?
Use historical performance for similar indications, adjust for eligibility stringency, and verify with feasibility surveys. Update the rate once actual screening logs are available.
What if enrollment ramps up over time?
Model the ramp using the startup delay or run multiple scenarios with different average rates for early and steady-state periods.
Does this account for site dropouts or pauses?
Not directly. If you expect site pauses or dropouts, reduce the active site count or enrollment rate to reflect the effective recruiting network.
Additional Information
- Result unit: months of enrollment duration after accounting for screen failures and startup delay.
- Screen failure defaults to 0% when left blank, assuming every screened patient enrolls.
- Startup delay defaults to 0 months and should capture site activation or protocol ramp-up time.