Any randomised controlled trial design that features an interim analysis used to review and potentially modify the trial design in key ways. These modifications ensure a more efficient trial overall.
In a cluster randomised controlled trial, participants are randomly allocated to either control or treatment arms at the membership (e.g. place of residence) rather than individual level. This type of design attempts to overcome issues of contamination, where it is impractical to administer a treatment to select participants (i.e. residents of a nursing home) only.
A crossover trial is a form of randomised control trial design in each participant is allocated to all available treatment arms over successive trial phases.
A randomised control trial design in which participants are randomly assigned to either two or more treatment arms to determine superiority, equivalence or non-inferiority.
A quasi-experimental randomised controlled trial design in which clusters of participant, defined by geographical, logistical, economic or political criteria, are randomised to commence treatment in sequential steps. Each cluster of participants receives both control and treatment interventions.
