Background: Prospective meta-analyses (PMA) may reduce many of the issues that can occur in retrospective meta-analyses, such as reducing biases in publication and selective outcome reporting. However, common misunderstandings of the PMA methodology remain, leading to inappropriate and/or suboptimal implementation by researchers.
Objectives: To investigate the landscape of the published and ongoing prospective meta-analyses.
Methods: We systematically searched the International Prospective Register of Systematic Reviews (PROSPERO) for PMAs from inception to January 2023, and two reviewers screened these studies in COVIDENCE. The results of this search were combined with a search of medical databases (PubMed, Embase, Cochrane Database of Systematic Reviews) up to 2018 to capture PMAs that started prior to the launch and subsequently increasingly wide implementation of PROSPERO in 2011. All PMAs conducted in human health research were eligible for inclusion. All records were double-screened, and data were double extracted, with conflicts resolved through consensus.
Results: We identified 1,445 studies in the PROSPERO search. One hundred thirty-two were screened at full text, and 32 were identified as PMAs. These identified PMAs were combined with the 43 articles of the second search of medical databases for extraction and analysis. We found that the number of published PMAs has been increasing over time (Figure 1). PMAs have been conducted across a range of health areas, and across all continents. Identified PMAs varied reporting on details, such as collaboration structure, or methods used to identify studies for inclusion. There were 1,091 records on PROSPERO that claimed to be a PMA but were found not to meet the eligibility criteria because they were including studies retrospectively.
Conclusions: Whilst PMAs are increasing in numbers, many researchers still do not understand what a PMA constitutes, with over 1,000 standard meta-analyses on PROSPERO falsely labelling themselves as PMAs. In addition, reporting of PMAs is currently inconsistent and lacks important details. Therefore, a standardised procedure for reporting PMAs and greater education on this method are crucial to facilitate the conduct and interpretation of impactful PMAs. This scoping review will help inform the development of such standardised reporting tools. Patient, public, and/or healthcare consumer involvement: None.