Updating the PRISMA reporting guideline for network meta-analysis: a scoping review

This scoping review is the first step in the process of updating the 2015 Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for network meta-analysis (NMA). It builds up on a 2014 scoping review by our team and aims to enhance the usability, completeness, and transparency of NMA reporting for diverse audiences, including patients and the public. The updated extension will align with PRISMA 2020 and will address gaps in reporting, such as documenting methods for assessing NMA homogeneity and transitivity, defining intervention nodes in a network of studies, and considering advances in statistical modeling with NMA.

We registered the study protocol with the Open Science Framework and published it in Joanna Briggs Institute (JBI) Evidence Synthesis. We searched multiple databases and gray literature sources, and screened studies in duplicate. Data extraction was also conducted in duplicate using a standardized form, focusing on study characteristics, authors' reporting recommendations, and proposed additions to PRISMA-NMA and/or PRISMA 2020.

Sixty-one studies met eligibility criteria, including 23 guidance documents and 38 overviews of reviews assessing the completeness or quality of NMA reporting. We identified 37 additional reporting items relevant to NMAs, which will inform the next stage of the PRISMA-NMA update (a Delphi consensus process).

Our findings support the urgent need to update the PRISMA-NMA guideline. Addressing persistent reporting gaps and incorporating recent methodological developments is critical to improving the transparency, reproducibility, and trustworthiness of NMAs.