Systematic Reviews & Evidence Synthesis Methods

Any time you search in multiple databases, there will be duplicate results. There are many different approaches and tools for removing duplicates (de-depulication), and they all have their pros and cons. No matter which approach you choose, keep track of result totals before and after deduplication in your PRISMA diagram!

Recommended Tools:

• Zotero - Zotero is a citation manager that is free and open source. It's deduplication tool is not perfect, but it allows you to make decisions and will not remove anything it considers a duplicate unless you tell it to.
  • For more information, check out this video on Identifying and Merging Duplicates in Zotero.
• EndNote - EndNote is a Clarivate product and has both a free basic version (online) and a more sophisticated paid version (desktop version plus an online component for sharing libraries). The online version of EndNote is more limited compared to the desktop version. For the desktop version,
  • View instructions and video: Steps to Remove Duplicates from your EndNote Library
  • You can set the parameters that are used to compare references in the deduplication process.  By default, the title, authors, year, and reference type are the fields that are compared. Go to "Preferences" to edit the fields being compared.  See the instructions and video:  Customizing Find Duplicates Search in EndNote
• Systematic Review Accelerator: Deduplicator - This free tool created by the Institute for Evidence-Based Healthcare compares results across multiple databases, and sorts records by their likelihood of being a duplicate, allowing for rapid removal of duplicate records. View helpful instructions here.

Other Options:

• Mendeley - This is another free citation manager that is a product of Elsevier. Mendeley auto-deduplicates, which is not recommended for systematic reviews.
• Rayyan - Rayyan is a free and open source screening tool. It has deduplication abilities, but they are not as user friendly as the others. Because Rayyan is browser-based, it tends to be somewhat less reliable when it comes to deduplication. (Recommended as secondary de-duplication)
  • For more information, check out this Rayyan Tutorial video.
• Covidence - If your team invested in this fee-based product, you will find that it does a very good job of deduplicating. As you import your result files, it will automatically run its deduplicator. This product also has an embedded PRISMA flowchart and will populate the fields automatically. Information and video: How to Manage Duplicates
• Excel - This is the option requiring the most work by you and many researchers like it because they control the full process. (Recommended as secondary, "by-hand" deduplication)