“Data collected from studies in a review can be used for updating the review only if the forms for the original review and the update included identically constructed items or questions. Instead of duplicating previous data abstraction efforts, a new systematic review could build on previous work and leverage the often-limited resources by using common data elements. Such elements help to ensure that data are captured and recorded uniformly and that the same data items, measurements, and observations are collected, defined consistently, and stored in the same format (such as numerical vs. character), thereby enhancing enhancing data quality and facilitating data reporting, sharing, and archiving.”(1)
As the quote above suggests, the data extraction stage of a review is important both for the review underway and future updates. The sources for data in a systematic or scoping review are typically the journal articles, but can include trial registers, conference abstracts, clinical study reports, and so on. According to the Cochrane Handbook, the type of data you plan to extract should be decided upon prior to undertaking the review and should be detailed enough to describe the study, have the ability to be used in tables and figures, help reduce bias, and help with synthesis and meta-analysis.
Data extraction should also be done by two independent reviewers in order to control for bias and maintain accuracy.
Some examples of the type of data include: (2)
*Please note: York University Librarians will not participate in this stage of the review, but will happily help with finding resources that may be of assistance.
Sources:
1. Li T, Vedula SS, Hadar N, Parkin C, Lau J, Dickersin K. Innovations in data collection, management, and archiving for systematic reviews. Ann Intern Med. 2015;162(4):287-94.
2. Li T, Higgins JPT, Deeks JJ (editors). Chapter 5: Collecting data. In: Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.3 (updated February 2022). Cochrane, 2022. Available from www.training.cochrane.org/handbook.