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Abstract
Objective
To examine the methodological characteristics of systematic reviews and meta-analyses
including observational studies (OSs) and randomized controlled trials (RCTs), in
various medical disciplines.
Study Design and Setting
We searched Medline via PubMed to identify systematic reviews of interventions including
RCTs and OSs published in 110 journals from 2015 to 2019. We extracted in duplicate
general and methodological characteristics of the systematic review.
Results
We identified 402 systematic reviews. Only 39% (n=160) of them reported the availability
of a pre-established protocol. A rationale for including observational data in the
systematic review was clearly reported in 25% (n=102) of the systematic reviews. Thirty-two
percent (n=130) of the reviews reported a search strategy intending to identify published
and unpublished data for RCTs and OSs. The risk of bias of the individual studies
was assessed in 89% (n=359) of the systematic reviews. In 74% (n=266) it was assessed
for both RCTs and OSs; 180 (50%) used different tools. Information about confounding
factors was reported in only 11% of systematic reviews and the type of effect estimates
(crude or adjusted) used was specified in only 22% of the systematic reviews. Among
the 385 systematic reviews that performed data synthesis, only 132 (33%) pooled OSs
and RCTs in the same meta-analysis.
Conclusion
Including OSs in systematic reviews of interventions could provide useful information
but such an approach could also be misleading; thus, several methodological details
are needed to ensure appropriate handling of OS and valid results. Our study revealed,
though, that substantial methodological information is missing in reports published
in high impact factor general and specialty journals.
Keywords
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Article info
Publication history
Accepted:
February 2,
2023
Received in revised form:
January 6,
2023
Received:
September 5,
2022
Publication stage
In Press Journal Pre-ProofIdentification
Copyright
© 2023 Elsevier Inc. All rights reserved.
