Information management during a complex meta-analysis: A practical guide for organizing data extraction.

Information management is a key part of conducting a systematic review and meta-analysis. Preferred Reporting Items for Systematic Reviews and Meta-Analyses clearly summarizes essential steps during the meta-analytic project and their reporting. Preparing for data extraction is generally suggested to be done at the stage of the protocol. However, in complex projects that aim to synthesize data from studies performed over a long time period or with a wide variability in study protocols, it is often impossible to fully account for all variations in data presentation before completing the full text screening. Here, we describe a protocol to methodically consider different aspects of the selected studies in order to update the data extraction template for the meta-analytic portion of the project. The protocol incorporates a process of identifying and removing non-compatible studies prior to the extraction of study-level outcomes, which is important for avoiding a potential confirmation bias. Using this protocol in combination with a pre-established data coding scheme simplifies data extraction and informs the subsequent meta-analysis.