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Comprehensive & Systematic Reviews

A guide to resources to help with conducting comprehensive reviews & services available from eTreadwell librarians

Steps to the Systematic Review Process

  1. Define your research question. Be as specific as possible, using operational definitions when appropriate.
  2. Based on your question, determine whether a systematic review is the best methodology for your review. See Grant's overview of 14 review types and methodologies. Also consider your available time and capacity. Will your team be able to systematically screen thousands of citations?
  3. Identify prior systematic reviews related to your topic. A librarian can help with this. Identifying prior systematic reviews can help you define the scope of your research question and determine how your review whether your review will add to the literature or merely replicate past work.
  4. Assemble your team. Generally, you will want at least two people to screen citations in order to reduce bias, someone with expertise in data synthesis (qualitative, quantitative, or mixed methods, depending on your plan), and an expert searcher (like a Treadwell librarian). 
  5. Determine study inclusion and exclusion criteria.
  6. Develop a plan of organization for your data. How will you keep track of the citations that you find? What is your plan for bias assessment/quality assesment, data extraction, and data synthesis?
  7. Formulate your research protocol. The PRISMA-P standards and checklist can be used to help you structure your protocol. It is recommended that you register your protocol in PROSPERO, an international systematic review protocol registry. The process of registration is straightforward and their guidance notes will tell you exactly what information to include.   
  8. Conduct a thorough literature search.
    1. Select databases to search. 
    2. Create a concept table with keywords.
    3. Incorporate database specific controlled vocabulary.
    4. Use filters and limits when appropriate.
    5. Test the search in one database.
    6. Translate the search for your other databases.
    7. Execute final searches.
    8. Export the results into citation management software and deduplicate the results.
  9. Select studies for inclusion.
    1. Use a random sample of your results to test interrater reliability & inclusion/exclusion criteria.
    2. Screen titles/abstracts.
    3. Resolve disagreements between screeners.
    4. Obtain full text and review full text, noting reasons for exclusion. 
    5. Resolve disagreements between screeners.
  10. Appraise the quality of the studies.
  11. Extract data using a standardized form. 
  12. Synthesize/analyze the data. 
  13. Interpret the results.
  14. Write up the report. 

How Long Does a Systematic Review Take?

Systematic reviews are work and time intensive! Estimates of the average time to conduct a systematic review range from 6-18 months (Source). A study examining the time between when systematic review protocols were registered in PROSPERO and when the systematic reviews were published reported the mean estimated time between registration and publication was 67.3 weeks (Source).

The Cochrane Collaboration has this to say about the timeline of systematic reviews:

The amount of time required will vary, depending on the topic of the review, the number of studies, the methods used (e.g. the extent of efforts to obtain unpublished information), the experience of the authors, and the types of support provided by the editorial team. The workload associated with undertaking a review is thus very variable. However, consideration of the tasks involved and the time required for each of these might help authors to estimate the amount of time that will be required. These tasks include training, meetings, protocol development, searching for studies, assessing citations and full-text reports of studies for eligibility, assessing the risk of bias of included studies, collecting data, pursuing missing data and unpublished studies, analyzing the data, interpreting the results and writing the review, keeping the review up to date. (Source)

Example timeline for a systematic review from the Cochrane Collaboration:

cochrane timeline

Isn't there a faster way? I don't have that much time!

Systematic reviews and meta-analyses are rigorous review methodologies and require a significant amount of time to conduct. If you need to conduct a review in less time, a different review methodology may be more appropriate, such as a:

  • Traditional narrative review
  • A systematic search and review
  • Rapid review

To compare and contrast these methodologies, please read Grant and Booth's "A typology of reviews: an analysis of 14 review types and associated methodologies."

Comparison of rapid review versus systematic review approaches.


Rapid review

Systematic review

Timeframe b

≤ 5 weeks

6 months to 2 years


Question specified a priori (may include broad PICOS)

Often a focused clinical question (focused PICOS)

Sources and searches

Sources may be limited but sources/strategies made explicit

Comprehensive sources searched and explicit strategies


Criterion-based; uniformly applied



Rigorous; critical appraisal (SRs only)

Rigorous; critical appraisal


Descriptive summary/categorization of the data

Qualitative summary +/- meta-analysis


Limited/cautious interpretation of the findings


Table from Khangura S, Konnyu K, Cushman R, Grimshaw J, Moher D. Evidence summaries: the evolution of a rapid review approach. Syst Rev. 2012;1(1):10. doi:10.1186/2046-4053-1-10.