Site enrollment

How to meet a clinical trial enrollment deadline

By TrialNotice · Updated
Research coordinator marking weekly enrollment targets on a wall calendar in a clinic office
Short answerMeet an enrollment deadline by working backward: convert your target into a weekly randomization rate, convert that into weekly screens using your screen failure rate, measure the funnel every week, and start every patient source before you need it, especially physician referrals, which take weeks to build.

How often do sites miss enrollment deadlines?

Often. In a typical trial, 37% of sites under enroll and 11% enroll no one (Tufts CSDD). Getz has noted that the majority of trials run late, by an average of six weeks (Applied Clinical Trials). Missing a deadline is the norm, which is why meeting one is noticed.

Why do deadlines slip?

  • Startup eats the calendar. Tufts CSDD measured 31.4 weeks from site identification to startup completion (Tufts CSDD), leaving less enrollment time than planned.
  • Screen failure is underestimated. The average is 36.3%, and 57% in CNS trials (Tufts CSDD).
  • Patient sources start too late. Most sites add sources only after falling behind.

How do you work backward from the deadline?

  1. Set the weekly rate. Illustrative example: 12 randomizations in 24 weeks is 0.5 per week.
  2. Convert to screens. At 36.3% screen failure, each screen randomizes 0.637 on average, so you need about 0.8 screens per week.
  3. Convert to referrals and prescreens. Apply your consent and prescreen conversion rates to find how many candidates each source must send.
  4. Assign sources. Records, physician referrals, and advertising each get a weekly target.

When should each patient source start?

Before activation. Record review and physician outreach can begin during startup within what your IRB and privacy procedures allow. Referral relationships take weeks to warm up, so letters sent at activation often produce referrals only after the first month. See how to reach first patient in faster.

What should you do when you fall behind?

  • Review the funnel weekly and act at the first two missed weeks, not the fifth.
  • Find the leaking stage: too few candidates, high screen failure, or consent drop off.
  • Tell the sponsor early. At $55,716 per day in direct Phase III costs (Tufts CSDD), sponsors prefer an early warning with a plan over a late surprise.

See the recovery plan for sites behind on enrollment.

Get your study in front of the right local physicians

TrialNotice builds a physician referral pipeline around one active study. We identify relevant local physicians within driving distance of your site, send study aligned direct mail, follow up by email and LinkedIn, track engagement with recipient level QR codes, and route warm responses into your site team's workflow.

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Sources

  1. Tufts CSDD, patient recruitment and retention practices study (Jan 2013), via Fierce Biotech
  2. Getz K., "Is Investigative Site Feasibility Feasible?" Applied Clinical Trials
  3. Applied Clinical Trials, "Can Recruitment and Retention Get Any Worse?" (Tufts CSDD screen failure study)
  4. Tufts CSDD, first comprehensive clinical site initiation benchmark (2018), via GlobeNewswire
  5. Tufts CSDD, "Quantifying the Value of a Day of Delay in Drug Development" white paper (2024)

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