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To summarize publically available guidance for, and current use of, meta-analytic methods for mixed treatment comparison (MTC) evidence synthesis; to identify analyses using these methods and summarize their characteristics; to gain insight regarding the rationale for selection, implementation, and reporting of such methods from investigators.
In part one, we identified currently available guidance documents addressing the use of MTC in evidence synthesis by searching governmental agencies' and participating members' of the International Network of Agencies for Health Technology Assessment Web sites. Commonalities and disagreements among guidance documents were summarized qualitatively. Next, in part two, a systematic literature search for MTCs was undertaken. Characteristics of included analysis were summarized qualitatively. Last, in part three, we invited a random selection of nine investigators from the systematic literature search to participate in a focus group. Using a Web-based series of questions, we queried respondents regarding their opinion of network meta-analysis and how elements of MTC methodology were chosen in their identified analysis. Responses were summarized qualitatively.
Guidance documents were typically written in a fashion to be applicable to network meta-analysis in general and not to a specific methodology. Guidance documents stressed Bayesian and Frequentist MTC approaches have strengths and limitations, while only one guidance document attempted to comprehensively address how to conduct a network meta-analysis and how to interpret and report results.
Our systematic review identified 42 MTCs of which the majority used Bayesian methods (80.9 percent). Bayesian analyses either used noninformative priors or did not report detail about priors used. Data regarding the evaluation of convergence, heterogeneity, and inconsistency were not consistently reported, and from those providing detail, it appears a broad range of methods were used.
Due to the infrequent use of Frequentist methods for MTC and poor response rate to our focus group invitation, all respondents had conducted a MTC using Bayesian methods. Consequently, we were unable to compare/contrast the viewpoints of investigators who used these two different methods.
Additional guidance on how and when to conduct a MTC, as well as how to interpret and report results is needed. Published meta-analyses using these methods varied in how they conducted and reported results.