Multisite studies create special access-control challenges. Staff at one facility may need to enter and review their own participants’ records but should not view participants from other facilities. Central teams may need oversight across all sites. Monitors may need access to selected sites. Statisticians may need combined de-identified datasets. Data Access Groups in REDCap support this separation by restricting users to records assigned to their group.

Data Access Groups are particularly important for confidentiality. A participant enrolled at one hospital may not expect staff at another hospital to view their identifiable data. Site-level separation reduces unnecessary exposure. It also supports accountability because each site can focus on its own records and performance indicators.
Configuring DAGs requires careful planning. Each site should have a clearly named group. Users should be assigned to the appropriate group. Records should be assigned to the correct group at creation or through a defined process. Central users who need access to all records should be configured appropriately and documented. The team should test access from the perspective of each role and site before production.
DAGs also affect reports. A site user may seeamissing-data report filtered to their own site, while a central data manager may see all sites. This is useful for site performance monitoring but can create confusion if users compare reports without understanding access restrictions.
Reports should be labeled clearly, and training should explain what each user can see. Multisite access control should be linked to governance. The protocol, ethics approval, data management plan, and site agreements may define who can access identifiable data. REDCap configuration should reflect these agreements. If access needs change, the change should be documented and approved.