Forecast recruitment with staggered site activation

Separate site count from active capacity

A study with several planned sites does not have the recruitment capacity of all sites from the first month. Approvals, contracts, staff training and local setup can produce staggered openings. Start with a calendar showing when each site can actually screen and enrol participants, rather than multiplying a mature monthly rate by the final site count.

The CONSORT pilot and feasibility extension supports transparent reporting of recruitment feasibility. The forecasting workflow here is an original planning aid: it translates site-specific assumptions into a calendar projection rather than treating a pilot recruitment total as guaranteed capacity.

Build the activation table

For each site, record the planned opening month, dependencies, responsible owner and evidence supporting the date. Separate an optimistic opening date from the current operational estimate. Define whether a partial month contributes a fraction of capacity or whether recruitment starts in the next full period.

Add a ramp-up assumption if new sites are unlikely to achieve their mature rate immediately. Distinguish eligible referrals, screening capacity and actual enrolment; the limiting step may change across sites. Record the mature rate's source and uncertainty rather than assigning every site the best-performing site's experience.

Hypothetical example

Three fictional sites open in months one, two and three. Each enrols ten participants per full active month, with no ramp-up in this simplified example. Expected enrolment is ten in month one, 20 in month two and 30 in month three: 60 across the first three months.

Assuming all three sites were open throughout would predict 90, overstating this scenario by 30. The six active site-months are one plus two plus three; multiplying them by ten gives the same total of 60. Real forecasts should also examine delays and uncertain rates.

Use the forecast to make a decision

Calculate cumulative enrolment by calendar month, not just total site-month capacity. Add follow-up time for the last expected enrolment when estimating the study completion date. Test scenarios in which an early site opens late or a high-volume site recruits more slowly than expected.

Track actual opening dates and enrolment against the forecast, with reasons for deviations. Use the recruitment monitoring trigger worksheet to define when corrective action is needed. A capacity forecast is not a sample-size justification and does not resolve selective recruitment. Keep the scientific sample target, operational forecast and observed recruitment record separate so each can be updated transparently.

Source verification: 6 November 2026. Examples are hypothetical.