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Systematic Reviews

This guide is intended for students, research assistants and faculty who are planning to undertake a systematic review, or who are interested in applying systematic research methods to a current project.

Step 5: Quality Assessment & Data Extraction

Quality Assessment - once you have completed the screening of your studies, you will have identified the ones which will be included in your review.  But you will still need to determine whether the studies are reliable.  In Chapter 4 of Doing a Systematic Review: A Student's Guide, the term 'quality' is described as "The degree to which a study employs measures to minimize bias and error in its design, conduct and analysis" (p. 65). 

There are numerous quality assessment protocols available - choose one which is appropriate to the types of studies you are considering in your systematic review.  A useful list of systematic review examples and the quality assessment strategies they used is in Ch. 7  of Systematic Approaches to a Successful Literature Review (2nd edition).  The Systematic Review Toolbox is an online tool that recommends quality assessment options based on your discipline, etc.

‚ÄčData Extraction - this allows the team to see the data from each individual research study in a comparative fashion, and at the  same time.  Identify the data you wish to extract - your data extraction form will likely replicate aspects of your PICO question  (Population, Intervention, Comparison, Outcomes). Build and test your data extraction form and/or data tables – Google Form could   be a useful tool here, or build tables in Word, Excel.  Communicate and collaborate if needed – if more than one person is involved   in data extraction, get on the same page.

Some examples of different approaches to data extraction and disply are viewable in the below articles:

• Narrative approach: Poulsen, M. N., McNab, P. R., Clayton, M. L., & Neff, R. A. (2015). A systematic review of urban agriculture and food security impacts in low-income countries. Food Policy, 55, 131-146. doi:10.1016/j.foodpol.2015.07.002
 
• Numerical approach: Azad, M. B., Abou-Setta, A. M., Chauhan, B. F., Rabbani, R., Lys, J., Copstein, L., Zarychanski, R. (2017). Nonnutritive sweeteners and cardiometabolic health: A systematic review and meta-analysis of randomized controlled trials and prospective cohort studies. CMAJ: Canadian Medical Association Journal, 189(28), E929. doi:10.1503/cmaj.161390