Randomisation: what is it and when is it necessary?

In a study comparing two or more treatments (one of which may be placebo), electronic randomisation ensures that allocation of patients to a treatment group is random.

Usually, this also ensures that unknown confounding variables are distributed evenly between the treatment groups. The randomisation tool should be reliable and easily available. To make sure that randomisation is carried out correctly, responsibility for the randomisation procedures should not lie with the research team. Computer-based methods for randomisation are more reliable and easier to use than manual methods.

What randomisation procedures do we follow?

We can offer stratification and block randomisation tailored to the specific study. The randomisation tool is web-based, and researchers can include patients on a 24 hour basis. At present (des 2009) more than 90 studies have used or use this tool for randomisation.

Each user of the randomisation program is given a unique user name. The user chooses a password, and has access only to his/her own study. When a new patient is included, standard screening questions must be answered correctly before it is possible to continue. Specific inclusion and exclusion criteria can be included at this stage to ensure correct inclusion.

Patients are identified by initials and age/year of birth in a section called Patient ID. This information is mandatory and prevents confusion between patients. Each user has access only to the patients at his/her hospital/centre, and it is not very likely that several patients at the same hospital will have the same initials and year of birth.

Stratification is carried out when required. Common procedures are stratification by centre/hospital, gender, age group and diagnosis. There is no limit to the number of strata, and this is adjusted as required for each study.

The tool uses block randomisation. The size of the first, smallest and largest blocks is established based on the total number of patients expected to be included in the study. The different treatments can be weighted if required. There is no limit on the number of treatments.

The results are shown on the screen after stratification is complete. Together with all data submitted for the patient in question, the result is emailed to the researcher who has included the patient and to the person responsible for the study.

Patient data submitted in the randomisation module cannot be changed, but corrections can be added in an open field at the bottom of each page. The complete list of randomised patients can be extracted as an Excel file.

Case report forms (CRFs) can be filled out using the same program WebCRF. This allows patient data from several hospitals/centre to be collected in the same database.

What do we expect you to do?

We need to know how many patients you intend to include, whether the treatments should be weighted, and whether stratification by hospital, age, gender or diagnosis will be necessary.

We also need to know how the strata will distribute the patients in groups, for example if a study will include approximately 20% women and 80% men. Stratification doesn't necessarily split the patient group in equally sized groups. This is important to be aware of when block sizes are to be set.

You must supply the name, hospital and email address for each researcher who is to have access to the database. We prefer researchers to carry out the randomisation process themselves, but it is possible to randomise patients by phone (daytime) if no Internet connection is available.

We can normally establish a new randomisation module within a few days, but more time is needed for large multi-centre studies.

Is the program secure?

The randomisation program is provided by the IT/Infrastructure Section at the Faculty of Medicine, which is responsible for technical support and for security. The security level is identical to that for NetCRF (more information available at this link).

What do we charge?

Research projects that are fully financed externally will be charged for our services. Researchers at the Faculty of Medicine and at hospitals in the Central Norway Health Region will not be charged.

Contact Berit M. Bjelkåsen for more information.