Everything appears ready. And in this moment — the moment between "eligible" and "enrolled" — I have seen more consequential errors than at any other point in the trial lifecycle.

Not errors of malice. Not errors of incompetence. Errors of assumption. The assumption that because the eligibility determination was thorough, the enrollment can proceed without further verification. The assumption that a consent form signed last Tuesday is still current today. The assumption that a hemoglobin drawn 26 days ago is still valid when the protocol specifies a 28-day screening window. The assumption that the investigator who reviewed the worksheet last Thursday has nothing further to consider today.

These assumptions are understandable. They are also dangerous. The enrollment decision is not a continuation of the screening process — it is a distinct regulatory act with its own verification requirements, its own documentation standards, and its own consequences when performed incorrectly. And unlike many errors in clinical research, enrolling an ineligible participant is not easily corrected. You cannot un-enroll someone. You cannot un-randomize them. You cannot undo the administration of an investigational product that has already been dispensed.

This lesson teaches the systematic pre-enrollment confirmation process that stands between a completed screening and the enrollment decision itself.

Everything appears ready. And in this moment — the moment between "eligible" and "enrolled" — I have seen more consequential errors than at any other point in the trial lifecycle.

Not errors of malice. Not errors of incompetence. Errors of assumption. The assumption that because the eligibility determination was thorough, the enrollment can proceed without further verification. The assumption that a consent form signed last Tuesday is still current today. The assumption that a hemoglobin drawn 26 days ago is still valid when the protocol specifies a 28-day screening window. The assumption that the investigator who reviewed the worksheet last Thursday has nothing further to consider today.

These assumptions are understandable. They are also dangerous. The enrollment decision is not a continuation of the screening process — it is a distinct regulatory act with its own verification requirements, its own documentation standards, and its own consequences when performed incorrectly. And unlike many errors in clinical research, enrolling an ineligible participant is not easily corrected. You cannot un-enroll someone. You cannot un-randomize them. You cannot undo the administration of an investigational product that has already been dispensed.

This lesson teaches the systematic pre-enrollment confirmation process that stands between a completed screening and the enrollment decision itself.