Abstract
BackgroundNetwork meta-analysis (NMA) has become a popular method to compare more than two treatments. This scoping review aimed to explore the characteristics and methodological quality of knowledge synthesis approaches underlying the NMA process. We also aimed to assess the statistical methods applied using the Analysis subdomain of the ISPOR checklist.MethodsComprehensive literature searches were conducted in MEDLINE, PubMed, EMBASE, and Cochrane Database of Systematic Reviews from inception until April 14, 2015. References of relevant reviews were scanned. Eligible studies compared at least four different interventions from randomised controlled trials with an appropriate NMA approach. Two reviewers independently performed study selection and data abstraction of included articles. All discrepancies between reviewers were resolved by a third reviewer. Data analysis involved quantitative (frequencies) and qualitative (content analysis) methods. Quality was evaluated using the AMSTAR tool for the conduct of knowledge synthesis and the ISPOR tool for statistical analysis.ResultsAfter screening 3538 citations and 877 full-text papers, 456 NMAs were included. These were published between 1997 and 2015, with 95% published after 2006. Most were conducted in Europe (51%) or North America (31%), and approximately one-third reported public sources of funding. Overall, 84% searched two or more electronic databases, 62% searched for grey literature, 58% performed duplicate study selection and data abstraction (independently), and 62% assessed risk of bias. Seventy-eight (17%) NMAs relied on previously conducted systematic reviews to obtain studies for inclusion in their NMA. Based on the AMSTAR tool, almost half of the NMAs incorporated quality appraisal results to formulate conclusions, 36% assessed publication bias, and 16% reported the source of funding. Based on the ISPOR tool, half of the NMAs did not report if an assessment for consistency was conducted or whether they accounted for inconsistency when present. Only 13% reported heterogeneity assumptions for the random-effects model.ConclusionsThe knowledge synthesis methods and analytical process for NMAs are poorly reported and need improvement.
Highlights
Network meta-analysis (NMA) has become a popular method to compare more than two treatments
Pairwise meta-analyses are limited by the availability of randomised controlled trials (RCTs) that directly compare one treatment relative to another
The indirect method implies that the information available from RCTs of treatment A and treatment B can be compared via a common comparator C by statistically combining the information from RCTs comparing A versus C and B versus C [4]
Summary
Network meta-analysis (NMA) has become a popular method to compare more than two treatments. Healthcare professionals and decision-makers increasingly rely on knowledge syntheses, such as systematic reviews and meta-analyses, to keep abreast of the literature and inform decisions based on the totality of evidence [1, 2]. Pairwise meta-analyses are limited by the availability of randomised controlled trials (RCTs) that directly compare one treatment relative to another. This can be problematic when comparing the efficacy of multiple competing interventions, since it is unlikely that RCTs provide direct comparisons for all interventions of interest [4,5,6]. Other terms used for NMA include mixed-treatment comparisons meta-analysis or multiple treatments meta-analysis [9, 10]
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