Glossary for systematic reviews and meta-analyses.

A systematic review aims to answer a focussed research question through a structured review of the evidence, using a predefined methodology, which often includes a meta-analysis. A meta-analysis is a statistical method used to combine the effect estimates from the individual studies included in a systematic review. Systematic reviews and meta-analyses are positioned at the highest level in the hierarchy of clinical evidence. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement was introduced in 2009 to help authors improve the quality and reliability of systematic reviews and meta-analyses. Recently, the volume of systematic reviews and meta-analyses in the field of Endodontology has increased; however, the quality of the published manuscripts has been reported to be sub-optimal, which does not take account of the systematic reviews that were rejected because of more obvious deficiencies. The aim of this paper is to present a comprehensive glossary of terminology commonly used in systematic reviews and meta-analyses in an attempt to provide easily understood definitions and explanations to assist authors when reporting systematic reviews and meta-analyses and to allow those wishing to read them to become better informed.