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REDCap: Identifiers

What Fields Should Be Marked as Identifiers in REDCap?

Each data field that could be considered a PHI identifier should be marked as an identifier in REDCap. Note this may differ from what is considered identifying or sensitive information for other aspects of your project (such as IRB approval.)

The following data elements should be considered potential identifiers per UW-Madison KnowledgeBase:

  • Dates (all elements of dates (except year) related to an individual. This includes dates of admission, discharge, birth, death. For individuals over 89 years old, the year of birth must not be used)
  • Names (this includes parts of names, such as initials)
  • Geographic subdivisions smaller than a state (including town, city, and zip code)
  • Phone numbers
  • Fax numbers
  • Email addresses
  • Social security numbers (includes parts of SSNs, e.g. last 4 digits, and scrambled SSNs)
  • Medical record numbers
  • Health plan beneficiary numbers
  • Account numbers
  • Certificate/license numbers
  • Vehicle identifiers and serial numbers, including license plate numbers
  • Device identifiers and serial numbers
  • Web Universal Resource Locators (URLs)
  • Internet Protocol (IP) address numbers
  • Biometric identifiers (including finger and voice prints)
  • Full face photographic images and any comparable images
  • Note that subject ID or Record ID numbers should not be checked as identifiers. These numbers might be the only way to distinguish a record for users that export data and/or don’t have access to identifiers (per project specific permissions)

How to Mark a Field as an Identifier in REDCap


Marking Identifiers Using the Online Designer

If you are building an instrument using the Online Designer, you can mark a field as an identifier when you add it. Select that that the field is an identifier on the left side of the "Add New Field" pop-up window when you are adding or editing a field.

Screenshot points out Identifier field
Select "Yes" next to Identifier to mark a field as an identifier in the Designer editor

Using the "Check for Identifiers" Tool

You can use this tool when your project is in development mode, or while it is in draft mode before you submit changes for approval. This tool automatically checks the names and descriptions of your data fields to look for common keywords that indicate an identifier.
To use this tool, make sure your project is in Development mode or draft mode (for projects that are already in Production.) Navigate to "Project Setup" and the "Design your data collection instruments" box. There will be a small link under the buttons for Online Designer and Data Dictionary.

Screenshot points out Check for Identifiers link
In Project Setup select the "Check For Identifiers" link

The Check for Identifiers tool will bring up a checklist of all the fields it has found that may contain identifiers. If the checkbox is already checked, the field has been marked as identifier. You can edit the identifier designation from this page by checking or un-checking the boxes. Make sure to save your changes with the "Update Identifiers" button at the bottom of the page.

Screenshot highlights Update Identifiers button
Select the checkbox and click Update Identifiers to mark a field as an identifier using the "Check for Identifiers" tool

Using the data dictionary

You can mark identifiers when setting up or editing your project using the data dictionary. Your project's data dictionary will have a column labeled 'Identifier.' Mark fields as identifiers by changing the value to "Y" in this column.

Screenshot highlights 'Identifier' column
Add "Y" to the identifier column to mark a field as an identifier using the Data Dictionary

What is the impact of marking fields as identifiers in REDCap?

Important! When a field is marked as an identifier in REDCap, this only restricts access when data is exported!
Users who have "Read" or "View & Edit" access to an instrument will still be able to see data entered into fields marked as an identifier. This is true even if their export privileges only allow them to export de-identified data. For most projects, simply marking a field as an identifier in REDCap should not have significant impacts on how users interact with data in your REDCap project.

How to restrict user access to identifiers in REDCap

If you would like to restrict users from viewing (and not just exporting) identifiers that have been entered into your REDCap project, then you will need to segregate identifier fields within one or more instruments that have their access restricted.

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KeywordsREDCap, identifiers, PHI   Doc ID95449
OwnerAmy S.GroupSMPH Research Informatics
Created2019-10-29 16:50:43Updated2024-04-02 07:52:19
SitesInstitute for Clinical and Translational Research, SMPH Research Informatics , SMPH Research Informatics TEST
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