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Guidance on Enrollment:

Reporting Study Progress & Proposing Accrual Goals

Defining "Enrollment" for IRB Purposes

Enrollment progress is required to be reported at the time of continuing review and may be requested if necessary for IRB’s review of amendments or reportable events. 

For studies which involve interaction with subjects, whether in person or by other means (such as surveys done online or through the mail), the UCSD Office of IRB Administration (OIA) considers as “enrolled” any subject who has gone through the consent process and has agreed to participate in the study.

  • For studies with signed consent, that will include all subjects who have signed a consent form, including a consent which is for screening procedures only.
  • For studies with a waiver of documented consent (no signature, but still a consent process/discussion), that will include all subjects who have agreed to participate.
  • Subjects who later withdraw or fail screening still count towards the total enrollment number that should be reported to OIA.

 For studies that do not involve any contact with subjects, such as secondary use studies (e.g., chart reviews or analysis of existing biospecimens), the enrollment number reported at continuing review, when it is required, should reflect the number of living individuals whose data or specimens were collected for the purposes of the present study. Most secondary use studies will not require continuing review based on the regulatory criteria.


Regulatory guidance specifies that IRBs must review a study’s progress at the time of continuing review. This includes the progress of subject enrollment. The guidance tells us:

 “A marked difference between the actual and expected rates of enrollment or dropout, either at an individual site or in the study as a whole, may indicate a problem requiring further investigation…”
 “IRB review of this information may shed light on problems related to the conduct of the research.  For example, a high rate of subject withdrawal secondary to serious adverse events may indicate that the risks of the research are greater than expected…”

 OIA acknowledges that enrollment numbers used for a study’s data analysis may be calculated differently from the definition described above. For example, in a randomized clinical drug trial, the n used in the study’s data analysis would likely only include those subjects that were randomized and received at least one dose of study drug. However, the scope of the IRB’s responsibility to protect the rights and welfare of human subjects includes all living individuals that were involved in the research as subjects, rather than just those subjects that advanced sufficiently far into the study to be counted for data analysis purposes.

Determining the Accrual Goal for New Projects

Given the above, the accrual goal proposed to the IRB as part of a new project should take into account an estimated number of screen failures and withdrawals in addition to the actual n needed for the study’s data analysis.

 Regulations and institutional policy require that investigators conduct their study in accordance with the IRB-approved protocol as a matter of compliance. Regulatory guidance tells us:

 “As part of its initial review, the IRB will have approved the protocol, which typically includes the number of subjects expected to be enrolled at a particular site. An investigator who enrolls more subjects than the number allowed at that site may have violated the study protocol or conditions set by the IRB or FDA.”

 As such, Investigators should devise a means of tracking enrollment in accordance with the OIA’s definition to ensure compliance.


FDA Guidance for IRBs, Clinical Investigators, and Sponsors - IRB Continuing Review After Clinical Investigation Approval (February 2012)

OHRP Continuing Review Guidance (November 2010)