Enrollment is the process by which participants enter a clinical study. In order to be considered enrolled the participant must have been screened for eligibility and have provided informed consent. The process of enrollment is monitored carefully to ensure safety of the participants and internal validity of the investigation. Once entered, the subject must follow the protocol.

The number of enrolled subjects must only refer to the number of participants who are expected to complete the study and does not include those who failed the screening process. It is vital that the clinical trial be able to enroll the appropriate number of participants to ensure that the research questions are answered.

Source: U.S. Food and Drug Administration. (2017). Glossary of terms on clinical trials for patient engagement advisory committee meeting.