Background: despite the increasing popularity of systematic reviews (SRs), it's crucial to assess their certainty of evidence (CoE), since the design itself doesn't guarantee high CoE.
Objectives: to evaluate if CoE was reported in SRs in infertility journals and if they used appropriate wording to describe that CoE.
Methods: we selected five fertility journals with the highest impact factors. We performed a search on PubMed, identifying potential SRs with meta-analysis. We screened the studies by title and abstract and analyzed if they classified the evidence in the full text and in the abstract. When CoE was not evaluated, we analyzed it with GRADE. We described how often the authors used a tool for CoE and the level of the CoE published in the selected SRs. We also analyzed if using a tool for CoE was associated with the P-value and if the P-value was associated with the level of the evidence. Finally, we analyzed if the study authors made any effort to adapt the wording used in the abstract to the CoE and the magnitude of the described estimated effect.
Results: CoE was reported in 21.4% of the SRs and in <10% of the abstracts. Although we did not find important differences in the reports of CoE of those that showed statistically significant differences and those that did not, P-value was associated with the wording chosen by authors. In general, magnitude of the effect was not expressed with consistent wording in 54.8% (23/42) of the SRs, while level of CoE was not expressed with consistent wording in 92.9% (39/42). Whereas magnitude of the effect was more consistently expressed in studies with statistically significant findings, CoE was better expressed when the P-value was >0.05.
Conclusions: in major infertility journals, less than 25% of authors reported the overall CoE in systematic reviews. Authors still focus more on the discussion if the found difference was by chance or not, and less on limitations in the study design, imprecision, indirectness, inconsistency, and publication bias. Authors should make efforts to interpret results in the context of those evaluations.
Patient, public and/or healthcare consumer involvement: none.