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Summary

The goal of this tutorial is to show the process required to add multiple participants with customized unique identifiers. In our example, the study required two different participant records to be “linked” as a pair. Although a Record ID is a sufficient identifier, it does not have robust options for customization. Note: This method does NOT use REDCap’s optional Participant Identifier that is located in the Participant List. The variable name for REDCap’s optional Participant Identifier is [redcap_survey_identifier], and it does not capture imported data when using the data import tool, nor can the data inputted be pulled into a form/survey field. In other words, it is not a “Smart Variable”, as defined by REDCap.


Customize Unique Participant Identifier

  1. To create a customized unique identifier, first, add a field in a survey.
  2. In the example below, the unique identifiers are “email” and “Participant ID.” In this case, the “Participant ID” field is necessary in order to link one participant to another using a chosen naming convention.
  3. Edit the field(s) and add the @HIDDEN-SURVEY action tag to ensure the field(s) are not visible to participants. Choose an optional validation. We recommend to use validation to help generate actionable data sets. The example below validates the email field as an email address.
  4. Customize the survey settings and change the “survey-specific email invitation field” to the email variable, which in this example, is [email_var].


(Optional) Change the “survey-specific email invitation field” setting for all surveys.

  1. This is useful in order to pipe in the email variable or any other unique identifier besides the Record ID (which is done automatically by REDCap). In the example below, “email” and “Participant ID” are piped in from the first survey. Piping allows to take data input and output it into another variable….
  2. Create a “Descriptive Text” field in the surveys desired.
  3. To pipe in data, apply brackets at the beginning and end of a variable in the field label box.
  4. Place @READONLY and @HIDDEN-SURVEY action tags so that it is not visible to participants.
  5. (Optional) Customize the record dashboard so that a participant’s customized unique identifier is viewed next to their Record ID, as shown by the example.


  1. Navigate to the project setup
  2. Under “Enable optional modules and customizations”, click the “Additional customization” button.
  3. Check the “Designate a Secondary Unique Field” option. In the dropdown menu, select the unique identifying variable desired. As noted by REDCap, “When a value is entered or imported for the secondary unique field, it will be checked in real time to ensure it is not shared by another record, and if so, it will ask the user to enter another value.”


Link Participants

There is no true way to link one record to another. Instead, it is better described as relating one record to another. To “link” one participant to another, create an ID naming convention as an identifier. For example, Participant ID 10001 and Participant ID 10002. Where the number 1 at the beginning indicates the group, and the number at the end indicates the individual. The data export tool has filtering features which can organize the customized Participant ID’s in order.


Learn how to add participants with unique identifier en masse.


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