RandoWeb, an online randomization tool for clinical trials.

This article describes RandoWeb, a generic tool allowing online randomizations for clinical trials. It allows some users to specify the randomization methods to use, patient data to collect or compute, and other users authorized to access the tool and their rights. Randomization can be defined through a randomization list or by using a dynamic method such as minimization. The randomization lists can be stratified and use block decomposition to maintain the best possible balance between the arms of the trial, even for the case when a trial is stopped prematurely. The block definition used by RandoWeb is slightly different from the classical one and, in particular, allows blocks with non-integer sizes. In RandoWeb, patients can be assigned up to three numbers: a record number, most often externally defined; a randomization number mainly useful for unblinding; and a treatment number used for the management of undifferentiated medicine packaging.