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A Site Principal Investigator, often called a Site PI, is responsible for how a research site carries out a study. On a study day, that responsibility includes following the approved protocol, supervising delegated staff work, attending to participant safety, and ensuring that study records are handled accurately. The Site PI's role is oversight and accountability, not a promise that someone will qualify for or benefit from a study.
The study protocol guides what happens at a visit. It describes the required assessments, timing, monitoring, documentation, and follow-up for that particular study. The Site PI ensures the site is prepared to follow those requirements and that staff members work within their delegated roles. Some activities may be completed by other trained members of the research team, while the PI remains accountable for the site's conduct.
Participants may meet more than one person on a study day. A coordinator may help with visit logistics and documentation. A rater or clinician may conduct protocol-required assessments. The Site PI may perform, review, or supervise activities as the protocol and delegation plan require. If you are unsure who is doing what, it is reasonable to ask, 'What is this part of the visit for, and who can answer questions about it?'
Screening is separate from simply expressing interest in a study. The research team uses the study's process to review information and explain what comes next. A public listing can help you understand a study's purpose and status, but it cannot tell you whether you will enroll. The research team is responsible for explaining the study process and providing the private channel for any personal health discussion.
Before a visit, write down questions about the schedule, expected assessments, monitoring, and contact person for concerns. NIH's Clinical Research Trials and You resource can help you understand basic research terms, while ClinicalTrials.gov provides public study information. Use the research contact path to ask general questions and receive the next steps from the study team.