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Systematic Reviews: A How-To Guide

Step 6: Extract Data

The data extraction/collection step of the systematic review process is perhaps the most time and labor intensive. It is the process of extracting data from studies you considered relevant to your review and organizing that data in a way that will allow you to synthesize the evidence and make conclusions. Expect to:

  • Extract relevant data from each individual study
  • Have at least two independent reviewers extract the data to reduce bias and avoid mismatches (typos)  
  • Use spreadsheets, structured forms, or data collection software to keep this information organized and easily accessible 

What to extract?

Putting together a data collection form should be considered early in the systematic review process. There is not one form that will be applicable to all reviews as data collected will depend on your research question and inclusion criteria. 

Information commonly collected may include:

  • Article citation/author information
  • Study methods
  • Population/patient characteristics
  • Intervention and comparator group characteristics
  • Study outcome

The National Academies Press/IOM Manual has a good table outlining the Types of Data Extracted from Individual Studies