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Performing a randomisation

For trials set up for internet randomisation, a Randomise link will be shown in the top menu bar or a Randomisation form will be present in the CRF. Either route takes the user to the randomisation form that requests relevant participant information needed to perform the randomisation. The form will vary depending on the trial; each trial is individually configured. Administrative users will see a field to select the site the participant originates from. Investigators can only randomise for the site they are associated with and so will not see this option.

Once the form has been completed and submitted, the user will be asked to review the information they entered and check it is correct. They can return to the previous screen to change items if any are incorrect. To continue, and generate a randomised allocation, the user must enter their password and click on the Confirm button. If the randomisation succeeds, the user will be shown the randomisation code on-screen. For unblinded trials, the code shown is the actual treatment group. Some trials may display multiple codes (for example, where the amount of drug to be given depends on a participant's weight).

Randomisation may not succeed for trials with code lists if no randomisation codes are available for the site concerned. Depending on trial configuration, randomisation may also fail if a participant with the same details has previously been randomised (duplicate).

Telephone randomisation

For trials set up for telephone randomisation, the user may randomise a participant using a touch-tone telephone by calling the trial-specific telephone number. After authentication, the user will be asked a series of questions to collect stratification information and check eligibility. Once all information has been collected, the randomisation will take place and the randomised group or code will be announced to the caller. Telephone randomisations can be viewed in the online system in the same way as randomisations carried out online.


An email containing the randomisation group or code will be automatically sent out to all relevant users that have notifications enabled. Relevant users are those with permission to view the randomisation form for the participant. Randomisation notifications are also sent to all notification accounts.

We advise you not to rely solely on email notifications for critical tasks like prescribing, as email is inherently unreliable. For instance, if investigators print out the randomisation email to take to the trial pharmacy, allow an alternative such as printing the completed randomisation form.

Notifications are not sent to users with suspended accounts. Administrators can see the format of notification emails on the specification page.

Manual randomisation

Occasionally, it may be necessary to randomise a participant outside the randomisation system using an emergency procedure, such as giving the next treatment allocation from a pre-defined backup list. This is called a manual randomisation. To record the details of manual randomisations in the system, an administrator should click the Enter manual randomisation details link at the bottom of the randomisation form. This will reveal extra fields: date and time of randomisation, and randomisation group or code. For blinded trials with a code list, the code entered must match an unused code in the code list available at the site. However, expiry date (if set) is not checked so that historic records can be added. Once the form is saved, the randomisation is recorded and clearly marked as a manual randomisation. If your trial uses minimisation for balancing treatment groups, then manual randomisations will be taken into account for future randomisations.

Randomisation limit

A randomisation limit is enforced that prevents further randomisations taking place once the limit is reached. The limit can be seen on the specification page. Randomisations marked as in error do not count towards the limit.

Randomisation list

Some randomisation methods rely on a predefined randomisation list, whereas dynamic methods (such as minimisation) do not use a randomisation list. The randomisation method is shown on the specification page. The total number of unused allocations in the randomisation list will be displayed if applicable, and a report, 'Allocations available in the randomisation list', will show the number of used and available allocations by the levels of each strata. Randomisation will not be possible if there are no allocations available for the stratification factors that apply to the participant being randomised. Contact Sealed Envelope support if this happens, as it will be necessary to extend the randomisation list.

Randomisation disabled

If an administrator has disabled randomisation, it will not be possible to add a new randomisation form. The exception is that administrators can still record manual randomisations. Existing randomisation forms remain accessible for viewing and editing.

Randomisation form

The randomisation form behaves in the same way as other Red Pill forms with a few exceptions. Firstly, validation overrides are not enabled so that any errors in data-entry must be resolved before proceeding. Secondly, the review step is never disabled for the randomisation form, even if it is disabled for other forms in a Red Pill application.

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