Bias in randomised factorial trials

Statistics in Medicine:  June 4, 2013

Abstract

Factorial trials are an efficient method of assessing multiple treatments in a single trial, saving both time and resources. However, they rely on the assumption of no interaction between treatment arms. Ignoring the possibility of an interaction in the analysis can lead to bias and potentially misleading conclusions. Therefore, it is often recommended that the size of the interaction be assessed during analysis. This approach can be formalised as a two-stage analysis; if the interaction test is not significant, a factorial analysis (where all patients receiving treatment A are compared with all not receiving A, and similarly for treatment B) is performed. If the interaction is significant, the analysis reverts to that of a four-arm trial (where each treatment combination is regarded as a separate treatment arm).  Read more