REDCap Randomization Module

Randomization Module

University of Chicago | Center for Research Informatics | REDCap Randomization Module

Randomization is a process that assigns participants/subjects by chance (rather than by choice) into

specific groups, typically for clinical research and clinical trials. Example: each subject assigned to

receive either the new treatment or the control (placebo) treatment.

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 Helps you implement a defined randomization model within your REDCap project, by allowing

you to

1. Define all of the randomization parameters;

2. Create and upload your custom randomization table (ie, allocation list)

 Table serves as a lookup table for deciding how to randomize subjects/records

REDCap DOES NOT create the randomization table for you. This table must be generated outside of

REDCap using other software (e.g. SAS, Stata, R), most likely by the statistician/data analyst involved in

your project.

By letting you create your own allocation table outside of REDCap, it lets you and your team choose

exactly how you wish to structure your allocations and assignments. Examples: block sizes,

permutations, and stratification balancing

Goals of Randomization:

 To produce groups that are comparable (ie, balanced) with respect to known or unknown risk

factors.

 To remove bias (selection bias and accidental bias).

 To guarantee the validity of statistical tests.

 To balance treatment groups, stratification factors, or both.



When to randomize?

 After determining eligibility

 As close to treatment time as possible (to avoid death or withdrawal before treatment start).

User Privileges

User privileges can be set to allow only certain users to be able to set up the randomization, perform

the randomization, or view the allocation dashboard to view progress. If someone is given 'Randomize'

privileges, they will be able to view and modify any existing data already collected for the

randomization strata fields (if stratification is used) when they are performing the randomization, even

if they do not specifically have form-level rights to view the form on which a strata field exists. Thus

Randomize rights trumps form-level rights in this way, but only for the randomization strata fields.

University of Chicago | Center for Research Informatics | REDCap Randomization Module

Setting-up a Randomization Model

A randomization model defines how the subjects in the study are randomized. To start the process,

click on the "Enable" button under the “Enable optional modules..” under the "Project Setup" tab.

Next, click on the Randomization link under “Applications” on the left side menu.

Randomization Setup

The randomization model is defined via the "Setup" tab and consists of three main steps:

1. Define your randomization model

2. Download template allocation tables (as Excel/CSV files)

3. Upload your allocation table (CSV file)

Step1 - Define your Randomization Model

The first main step in the setup process is to define your randomization model you will be

implementing and all its parameters, which includes defining strata (if applicable) and optionally

randomizing subjects per group/site (if a multi-site study). In this step, you will define the type of

randomization and how the randomization is applied to the subjects. There are two randomization

types:

1. Use stratified randomization?

2. Randomize by group/site?

University of Chicago | Center for Research Informatics | REDCap Randomization Module

Use Stratified Randomization?

Stratified randomization ensures that different groups are balanced. The balance is specified in the

allocation table. Increasing the number of stratification variables will lead to fewer subjects per

stratum.

IMPORTANT: you must revise the data dictionary to include the needed fields to specify the

randomization model.

Randomize by Group/Site?

If this is a multiple site study, this option allows you to stratify the randomization by each group. When

this option is checked, you are given the opportunity to select randomization by data access groups or

by a REDCap drop-down list of the sites.

Choose your Randomization Field

This is the field that will receive the randomization group designation.

Once all parameters are set, save the randomization model.

University of Chicago | Center for Research Informatics | REDCap Randomization Module

Step 2 - Download template allocation tables (as Excel/CSV files)

The second main step in the randomization setup is to download the allocation table template.

Template allocation tables contain all the raw coded values for the fields used in your randomization

model.

 Will list each multiple choice option's label corresponding to each raw coded value for all the

fields utilized (e.g. it will specify 0=Female and 1=Male for the field 'gender').

 If you are using Data Access Groups to randomize by group, then it will additionally list each

group name with its corresponding group ID number.

Does not necessarily matter how you create or set up your allocation table so long as you structure it

correctly.

University of Chicago | Center for Research Informatics | REDCap Randomization Module

REDCap creates several example files to download that you may use as a structure when creating your

own randomization table. For this example, I have stratified a hair color field that has 7 different values

and I wish to allocate the participants into 5 groups. My allocation template downloaded from REDCap

looks similar to the following:

REDCap will randomize the participants according to this table. For example, the first participant that

has a hair color of "Light Blond" (corresponding to the value of one) will be allocated to random group

one. The second person with "Light Blond" will be allocated to random group two, etc. Note: Make

sure the number of entries in the randomization table is large enough to accommodate all participants

in each category.

University of Chicago | Center for Research Informatics | REDCap Randomization Module

In order to make the allocation schedule more difficult to predict, a temporary column can be added to

the spreadsheet for randomizing the order. The Excel function "RAND()" creates a random value

between 0 and 1. This number can be used as an easy way to populate a third column in the

spreadsheet with a unique random value. If the spreadsheet is sorted by this column, the group and

hair color values will be randomized. For example, after sorting, the spreadsheet may look similar to

the following:

After sorting the table by the random value, the column with the rand() function should be removed

before to saving the spreadsheet as a CSV file and prior to uploading it as the allocation table into

REDCap.

University of Chicago | Center for Research Informatics | REDCap Randomization Module

Step 3 - Upload your Allocation Table (CSV file)

The third and final main step in the randomization setup is to upload the allocation table.

Two allocation tables will eventually need to be defined, one for the development stage and a different

one for the production stage.

Randomization User Rights

There are several user privileges that can be utilized for randomization, all of which correspond to

different roles during the randomization process and can be set on the User Rights page.

 Setup: will see the Setup tab on the Randomization page, which will allow you to define the

randomization model and all its parameters, as well as upload your custom allocation table →

Statistician/data analyst

 Dashboard: will see the (Allocation) Dashboard tab on the Randomization page, in which you

may view the overall allocation progress and assignments for subjects that have been

randomized → Study’s PI

 Randomize: - will be able to view the Randomize button on the data collection form that contains

the randomization field, thus allowing you to perform the randomization on the subject/record

you are viewing → Research nurse/Study coordinator

Should

NOT be

the same

allocation

table.

University of Chicago | Center for Research Informatics | REDCap Randomization Module

Randomizing a Record

The fields that have been specified for randomization will now display a "Randomize" button in the

data entry screen. This will allow you to generate a random value according to the randomization

allocation table.

When a user (who has been given appropriate 'Randomize' user privileges) clicks that button, a pop-up

box will appear that will allow the user to randomize the subject/record. If any grouping or

stratification is being used, the user must provide the group or strata values if any are missing before

they can randomize the subject/record. Pressing the "Randomize" button gives you an opportunity to

double check the required values that will impact the definition of the resulting randomization group.

University of Chicago | Center for Research Informatics | REDCap Randomization Module

When the user randomizes the subject/record, REDCap will check the allocation table and assign that

subject's/record’s randomization field value, which will be derived from the next match in the table

based upon the criteria (eg, strata field values, group). If not using stratified randomization and not

randomizing by group/site, then it will simply provide the subject with the very next value in the

allocation table. After updating or providing missing values, a dialog of the random group that was

assigned is displayed.

In addition, after the value of the random group is assigned, the random group field becomes read-only

and the value cannot be changed.

The strata fields you have chosen also become read-only and cannot be changed.

University of Chicago | Center for Research Informatics | REDCap Randomization Module

A listing of the records that have been randomized is maintained. To examine those records, click on

the Randomization link in the Applications section of the Navigation Pane.

Dashboard

A dashboard displaying the allocated records and the random group assigned are shown below:

University of Chicago | Center for Research Informatics | REDCap Randomization Module

IMPORTANT

 How you generate your allocation table should be formal, secure, reproducible, and

unpredictable → Best handled by a statistician; NOT the PI.

 Be sure to include more assignments in your allocation table than you think you will need (to

accommodate possible drop-out and drop-in of subjects).

 The Setup tab on the Randomization page is ONLY available while the project is in

Development status.

 Once the project is in Production, the Setup tab will become permanently locked and no

settings can be modified, nor can any assignments be undone.

 Practice the process of randomizing patients by uploading an allocation table while in

Development status and creating dummy records.

 Delete the dummy records and upload “final” allocation table before moving to

Production status.