A novel approach for visualizing local consistency in network meta-analysis

Network meta-analysis is the established method to pool evidence from multiple clinical trials and make direct and indirect comparisons between different treatments. To ensure its validity, one of the major assumptions requiring examination is that the different sources of information are consistent, which is to say that the direct and indirect effect estimates agree. There are at least three different aspects to consider: (1) the original effect sizes of the direct and indirect treatment effects and their relative contribution to the total evidence; (2) the difference between them and its associated uncertainty/significance; and (3) the type of difference between them, that is, whether the direct and indirect estimates agree that a treatment is beneficial or harmful. Current visualization approaches typically use forest plots or heat maps, but these are limited as at least one of the above aspects is usually absent. Furthermore, as the number of treatments in the network increases, these visualizations can become difficult to understand. We present a visualization that combines the three aspects without being too difficult to interpret, outline the mathematical background and provide the code to produce it in R.