“…In addition, we cannot fail to mention that, despite being secondary studies, meta-analyzes may raise doubts regarding the compliance with ethical and legal principles, particularly in terms of the accuracy and adequacy of the findings (Li et al, 2011). The simplest application of a network meta-analysis for indirect and mixed comparisons consists of determining if treatment B is better than treatment A, and if treatment C is better than the same comparator A, taking into account the lack of studies directly comparing B and C (Tobías et al, 2014; Figure 1A). Thus, several statistical methods can be used to perform indirect comparisons that can combine data from preliminary studies when these are limited or simply non-existent ( Figure 1B), such as: the Bucher's method (Bucher, Guyatt, Griffith, & Walter,1997), also called the method for adjusted indirect comparisons; the meta-regression (Bayesian and frequentist inference approaches); and the hierarchical Bayesian models based on the Markov chain Monte Carlo (Catalá-López & Tobías, 2013;Tobías et al, 2014).…”