Data extraction, which follows full-text screening, is the systematic process of transcribing key information from primary studies included in the review. Extraction is done by two reviewers independently to reduce bias and increase accuracy.
Data can be extracted and recorded using:
Plan carefully to ensure the data you extract will allow you to answer your research question. Pilot test your data extraction form to ensure it is clear and comprehensive.
If published data is missing or unclear, try contacting the study authors for details.
Critical appraisal is a key component of many evidence syntheses reviews.
"Critical appraisal is the process of carefully and systematically examining research to judge its trustworthiness, and its value and relevance in a particular context" (Burls, 2009).
Generally, the critical appraisal process will consider:
To determine if your evidence synthesis review requires critical appraisal, consult this chart which outlines 14 types of review articles and indicates whether quality appraisal is typically included. Table 1: Main review types characterized by methods used (Grant & Booth, 2009).
When reading the full text of each article identified for inclusion in the review as part of the data extraction process, apply a Critical Appraisal Tool to each study selected for inclusion. Select a critical appraisal tool appropriate for the study designs you are reviewing.
Systematic Reviews in Health by Murray Turner at University of Canberra
Systematic Reviews by Lydia Thorne at University of Ontario Institute of Technology
Systematic reviews and other syntheses by Sandra McKeown, Queen's University Library
Burls, A. (2009). What is critical appraisal? Hayward Medical Communications.
Grant, M. J., & Booth, A. (2009). A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26(2), 91-108.