Randomization
What is randomization?
Randomization is a process that assigns participants/subjects by chance (rather than by choice) into specific groups, typically for clinical research and clinical trials.
The randomization module in REDCap will help you implement a defined randomization model within your project, allowing you to randomize your subjects (i.e. records in your project). In this module, you first define the randomization model with various parameters. Based on the defined parameters, the module creates a template allocation table, which you can use to structure the randomization table you will import. The module also monitors the overall allocation progress and assignment of randomized subjects.
REDCap’s Randomization Module
Enabling Randomization
Enabling the randomization module requires the Project Design and Setup user privilege.
Project Setup > Enable optional modules and customizations > Randomization module
Randomization User Privileges
Once the module is enabled, the Randomization privileges appear when assigning user privileges.
Existing users will need to be given rights to use the module.
Setting up Randomization
Setting up the randomization module requires the Randomization: Setup user privilege. On the Randomization page, click “+ Add new randomization model”
If required, REDCap can support multiple independent randomization models in the same project.
Next, setup your randomization model. Note that these options cannot be changed after they are saved:
REDCap supports stratified randomization by multiple choice fields (radio, dropdown) and by DAG.
There are 2 randomization types. These types are selected based on the randomization variable’s field type.
Once the randomization model is defined, the next step is to upload the desired randomization allocation table. Template allocation tables are available to give an idea of what your allocation table should look like to be understood by REDCap. The allocation table is used for testing (development status) must be different from the one used in production.
Lastly, randomization can be manually triggered (i.e., a randomization button) or automated to occur once a defined trigger logic is met.
It is recommended that only people with experience in randomization set up the Randomization module. Contact Us if you would like support in setting up randomization.
Open randomization
Randomization variable field type: multiple choice (radio or dropdown)
Example: multiple treatments where the assignment type is visible within REDCap
In this mode the exact allocation table is obscured, and those with Randomization Dashboard permissions can see an overview of each treatment type:
Example of the randomization field before & after randomization:
Concealed (blinded) randomization
Randomization variable field type: text, no validation
Example: multiple treatments where the assignment type is obscured within REDCap, such as when bottle IDs map to specific contents and the mapping is not seen within REDCap.
In this mode the exact allocation table is obscured, and those with Randomization Dashboard can only see the number of allocations & the records assigned an allocation.
Example of the randomization field before & after randomization:
Note: in the allocation table, it is optional to include the redcap_randomization_group. Like the allocation table sequence, this information is not visible within REDCap except by CHI REDCap admins, who can use the information to aid in randomization troubleshooting. Here is an example allocation table that has included the treatment group information:
Allocation Dashboard
Viewing the dashboard requires the Randomization: Dashboard user privilege.
The dashboard gives an overview of the randomization assignments thus far. It displays how many of the assignments are used and how many are unused.
For concealed (blinded) randomization, the treatment group assigned is not seen.
Randomizing a Record to a Group
Manual, using Randomize button (default)
In the data entry form, those with Randomization Randomize permission can click the “Randomize” button to assign the next treatment in the allocation sequence. The randomized field (and any fields used for stratification) cannot be edited after randomization (except by REDCap admins. Please see Contact Us for our support if you require help with randomization allocation).
If stratification is used, someone with 'Randomize' privileges can view and modify any existing data already collected for the randomization strata fields, even if they do not specifically have form-level rights to view the form on which a strata field exists.
A user with the ‘Randomize’ privilege will have the option to perform randomization. Once a record is randomized to a group, its allocation (and the data in the strata fields, if any) cannot be changed.
Automated randomization using Trigger Logic
A user with Randomization Setup permissions can setup trigger logic.
The “Randomize” button will still appear for manual randomization, but this expands functionality by allowing for randomization to be automated depending on whether a trigger is met.