Figure 4

Biased network meta-analysis of AB trials (comparing treatment B relative to A) and AC trials (comparing treatment C relative to A). (a) Forest plot of four AB studies and four AC studies. There are no differences in the effect modifier across studies within comparisons, but an imbalance in the distribution of the effect modifier between comparisons. Hence, there is no between-study heterogeneity, but a biased indirect comparison estimate of C vs B. (b) Forest plot of four AB studies and four AC studies. There are differences in the distribution of the effect modifier across studies within comparisons, as well as an imbalance in the distribution of the effect modifier between comparisons. Hence, there is between-study heterogeneity, and a biased indirect comparison estimate of C vs B.