Appraisal methods and outcomes of AMSTAR 2 assessments in overviews of systematic reviews of interventions in the cardiovascular field: A methodological study

This study aimed to assess the methods and outcomes of The Measurement Tool to Assess systematic Reviews (AMSTAR) 2 appraisals in overviews of reviews (overviews) of interventions in the cardiovascular field and identify factors that are associated with these outcomes. MEDLINE, Scopus, and the Cochrane Database of Systematic Reviews were searched until November 2022. Eligible were overviews of cardiovascular interventions, analyzing systematic reviews (SRs) of randomized controlled trials (RCTs). Extracted data included characteristics of overviews and SRs and AMSTAR 2 appraisal methods and outcomes. Data were synthesized using descriptive statistics and logistic regression to explore potential associations between the characteristics of SRs and extracted AMSTAR 2 overall ratings ("High-Moderate" vs. "Low-Critically low"). The original results on individual AMSTAR 2 items were entered into the official AMSTAR 2 online tool and the recalculated overall confidence ratings were compared to those provided in overviews. All 34 overviews identified were published between 2019 and 2022. Rating of overall confidence following the algorithm suggested by AMSTAR 2 developers was noted in 74% of overviews. The 679 unique included SRs were mainly of "Critically low" (53%) or "Low" (18.7%) confidence and underperformed in items 2 (Protocol, no = 65.2%) and 7 (List of excluded studies, no = 84%). The following characteristics of SRs were significantly associated with higher overall ratings: Cochrane origin, pharmacological interventions, including exclusively RCTs, citation of methodological and reporting guidelines, protocol, absence of funding and publication after AMSTAR 2 release. Generally, overviews' authors tended to deviate from the original rating scheme and ascribe higher ratings to SRs compared to the official AMSTAR 2 online tool. Most SRs included in overviews of cardiovascular interventions have critically low or low confidence in their results. Overviews' authors should be more transparent about the methods used to derive the overall confidence in SRs.