SOLUTIONS TO HIGH-PRIORITY CHALLENGES IN SYSTEMATIC REVIEWS: Network meta-analysis and integrating randomized and non-randomized evidence

Abstract

Systematic reviews (SR) and meta-analysis (MA) of randomised controlled trials (RCT) are the trustworthy sources of evidence. However, most systematic reviews focus on pair-wise comparisons. Network-meta-analysis (NMA) offers quantitative methods of integrating data from all the available comparisons of many different treatments for each outcome. In a systematic review of interventions, Summary of Findings (SoF) tables present the main findings of a review in a transparent and simple form. However, it is unknown how to present NMA findings in a tabular format. Moreover, systematic reviews and meta-analysis of interventions can summarize bodies of evidence from randomized and non-randomized studies (NRS). Integrating both sources of evidence in a single study can be challenging particularly in the context of assessing the certainty of the evidence, as well as presenting findings of both RCTs and NRS sources of evidence. In our study, we described how 276 NMA were conducted and how authors reported their main findings. We also conducted 32 interviews with users of NMAs and we designed two final NMA-SoF tables. Furthermore, we conducted two systematic reviews that included RCTs and NRS to address methodological challenges. Based on our results, we developed two NMA-SoF table formats to report the main findings of NMAs. The final format was appealing for users and allowed them to better understand NMA findings. Assessment of quality of individual NRS remains challenging and further research is needed to increase its appropriateness in systematic reviews of NRS. We determined that quality assessment of individual NRS was particularly challenging to implement due to the complexity of NRS evaluation tools. Our evaluation revealed that effect estimates of RCTs and NRS were better presented separately.