Methodological review of NMA bias concepts provides groundwork for the development of a list of concepts for potential inclusion in a new risk of bias tool for network meta-analysis (RoB NMA Tool)

Abstract

Abstract Introduction: Network meta-analyses (NMAs) have gained popularity and grown in number due to their ability to provide estimates of comparative effectiveness of multiple treatments for the same condition. The aim of this study is to conduct a methodological review to compile a preliminary list of concepts related to bias in NMAs. Methods and Analysis: We included papers that present items related to bias, reporting, or methodological quality, papers assessing the quality of NMAs, or methods papers. We searched MEDLINE, the Cochrane library, and unpublished literature (July 2020). We extracted items related to bias in NMAs. An item was excluded if it related to general systematic review quality or bias, and included in currently available tools such as ROBIS or AMSTAR 2. We reworded items, typically structured as questions, into concepts (i.e. general notions). Results: 181 articles were assessed at full text and 57 were included. Of these articles, 12 were tools, checklists or journal standards, 12 were guidance documents for NMAs, 26 were articles related to bias or methods, and 7 were papers that assessed the quality of NMAs. These studies yielded 99 items of which the majority related to general systematic review quality and biases and were therefore excluded. The items we included were reworded into 22 concepts specific to bias in NMAs. Conclusions: A list of 22 concepts were included. This list is not intended to be used to assess biases in NMAs, but to inform the development of items to be included in our tool.