Mixed and Indirect Comparisons
Mixed and indirect comparisons are specialized methods of performing meta-analysis. These methods can be useful in replacing or augmenting a meta-analysis, but one must be aware of potential pitfalls when using them. This entry presents definitions, methods, assumptions, and examples of each of the terms.
A direct comparison of two interventions occurs when they are compared within the same randomized controlled trial (RCT). An indirect comparison is any method of comparing two interventions without the use of direct comparisons between the two. It can be used in meta-analysis of RCTs when a reviewer wishes to compare two interventions and no direct comparisons exist. It can also be used in conjunction with direct evidence to strengthen results.
There are two possible methods of performing indirect comparisons. One ...