Systematic Reviews

Role of the librarian in this stage

A librarian can advise you on study selection for your systematic review, including: 

  • How to use Covidence to screen citations and manage the screening process
  • How to apply your review inclusion and exclusion criteria to the screening process

Contact HSL About Your Review

Email us

Ready to start a systematic review? HSL Librarians can help!

Fill out the Systematic Review Request Form and the best-suited librarian will get back to you promptly. Our systematic review service is only available to faculty, staff, students, and others who are affiliated with UNC Chapel Hill.

Screening Results with Covidence

We recommend that systematic review teams use Covidence to screen results. Covidence is provided free from HSL and its partners, and there is no limit to the number of reviews that can be created.

How does screening work in Covidence?

Once you have completed literature searching and compiled all citations, it is time to screen the results. The purpose of screening is to eliminate studies that do not meet your inclusion criteria. Two independent reviewers should screen all studies, starting with a title and abstract screening, followed by a full-text screening. A third reviewer should resolve any conflicts.

During the title/abstract screening, for each reference, each reviewer should read the title and abstract and make a decision:

  • No: This article does not meet inclusion criteria and should not be included in the systematic review.
  • Maybe: There is not enough information in the title/abstract to make a decision (move to full-text screening stage).
  • Yes: This article appears to meet inclusion criteria and should move to the full-text screening stage.

During the full-text screening, for each reference, read the full-text and make a decision:

  • Include: This article meets inclusion criteria and should be included in the systematic review.
  • Exclude: This article does not meet inclusion criteria and should not be included in the systematic review.

Remember, all voting should be blinded, meaning team members should be unable to see how others cast their votes.

PRISMA statement

"PRISMA stands for Preferred Reporting Items for Systematic Reviews and Meta-Analyses. It is an evidence-based minimum set of items for reporting in systematic reviews and meta-analyses. The aim of the PRISMA Statement is to help authors improve the reporting of systematic reviews and meta-analyses. The PRISMA Statement consists of a 27-item checklist and a four-phase flow diagram." (From )

PRISMA and Covidence:

Covidence will track numbers of citations screened at each stage and how many are ultimately included in the review. These numbers can be copy and pasted into a PRISMA diagram template. A step-by-step guide on creating a PRISMA diagram is shown below.

PRISMA Step-by-Step

Step 1- Preparation: To complete the PRISMA diagram, download a copy to use alongside your searches. It can be downloaded from the PRISMA website. You will need a copy with totals from all the databases, but you may want to print out a copy for each database you search as well.

Step 2- Searching: Once all search terms have been combined and you have applied all relevant limits, you should have a number of records or articles. Enter this in the top left box of the PRISMA flow chart for each database. If you have searched databases individually, add up all the 'records identified,' and enter this total number in the PRISMA flow diagram.

PRISMA additional sources

Step 3- Additional Sources: If you have identified articles through sources other than databases (like manual searches through reference lists of articles you have found or Search engines like Google Scholar), enter the total number of records in the box on the top right of the flow diagram.

PRISMA diagram showing duplicates removed box

Step 4- Remove all duplicates: To avoid reviewing duplicate articles, you need to remove any articles that appear more than once. You will need to go through all the records or articles you have found in the database and manually remove any duplicates. This is not easy to do if you have a large number of articles at this point. In this case, you may want to export the entire list of articles to a citation manager such as EndNote, Sciwheel, or Zotero (including both citation and abstract in your file) and remove the duplicates there. Enter the number of records left after duplicate removal in the second box from the top.

PRISMA records screened

Step 5- Screening Articles: The next step is to add in the number of articles that you have screened. This is the same number as you have entered in the duplicates removed box.

PRISMA records excluded box

Step 6- Records Excluded: You will now need to screen the titles and abstracts for articles which are relevant to your research question. Any articles that appear to help you provide an answer to your research question should be included. Record the number of articles excluded based on this screening process in the appropriate box (next to the total number of screened records) with a short reason for excluding these articles.

PRISMA eligability box

Step 7- Eligibility: Subtract the number of articles excluded during the screening phase (step 6) from the total number of records screened (step 5) and enter this number in the box titled "Full-text articles assessed for eligibility." Get the full text for these articles to review them for eligibility. You can request articles through Interlibrary Loan to ensure that you get access to most research.

PRISMA full text articles excluded

Step 8- Full-Text Articles Excluded: Review all full-text articles to determine which ones are eligible to be included in the final review. Take a note of the number of articles that you exclude at this point and enter this number in the box titled "Full-text articles excluded." Then write in a short reason for excluding the articles (this may be the same reason used for the screening phase). Examples include wrong setting, wrong patient population, wrong intervention, wrong dosage, etc.

PRISMA articles excluded

Step 9- Included: The final step is to subtract the number of excluded articles or records during the eligibility review of full texts (step 8) from the total number of articles reviewed for eligibility (step 7). Enter this number in the qualitative synthesis box. If you perform a meta-analysis, you would also list the number of studies in the quantitative synthesis box. You have now completed your PRISMA flow diagram, which you can now include in the results section of your article.

Adapted from GCU

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