RESUMO
The validity of primary study results included in systematic reviews plays an important role in drawing conclusions about intervention effectiveness and carries implications for clinical decision-making. We evaluated the prevalence of methodological quality and risk of bias assessments in systematic reviews published in the five highest-ranked anaesthesia journals since 2007. The initial PubMed search yielded 315 citations, and our final sample after screening consisted of 207 systematic reviews. One hundred and seventy-four reviews conducted methodological quality/risk of bias analyses. The Jadad scale was most frequently used. Forty-four of the 83 reviews that included high risk of bias studies re-analysed their data omitting these trials: 20 showed differences in pooled effect estimates. Reviews containing a greater number of primary studies evaluated quality less frequently than smaller reviews. Overall, the majority of reviews evaluated bias; however, many applied questionable methods. Given the potential effects of bias on summary outcomes, greater attention is warranted.
