What should a good systematic review contain?

Good systematic reviews focus on a clear question in which all the elements for the PICO acronym can be found back: participants, intervention or exposure, control condition and outcome. Inclusion of studies in the review is based on clear criteria. A thorough and systematic search of multiple databases should garantuee that all available evidence is located. Assessment of the risk of bias of the included studies provides an understanding of the quality of the evidence in the review. Proper synthesis methods should safeguard that not apples and pears are combined. In such a way, systematic reviews provide a reliable and transparent overview of the available evidence.