Systematic review guide

Do not move on to this stage until you have tested your search strategies and know that they are finding all the relevant articles to answer your research question. 

Once you are confident that you have comprehensive search strategies, it is time to move your results into reference management
software. This will:

• Allow you to remove duplicate article records

• Help you organise and keep track of your search results

• Ensure that they are correctly cited when you write your review

To help you work out which software package is best for you, we have created a reference management software comparison (pdf) of some of the most popular options. We support EndNote and RefWorks, and provide advice on Mendeley and Zotero. You can find more details about these at Reference management.

If you have any questions about this stage of the process, your subject librarian will be happy to help. Please see the homepage of this guide for contact information.

At the same time you run your final search on each database and export the results, remember to also export or copy your search history and strategy and to note the final number results found for each search and the dates the searches were completed. Instructions for exporting search histories can be found in Documenting the search.

Once you have exported your search results into your chosen reference management software, you will need to remove duplicate records as there is likely to be considerable overlap in the results of your various database searches and you don't want to be screening the same reference twice. Most reference management software includes a feature to help you remove or merge duplicate records.

Before you remove any duplicates

It is important to prepare for documenting how many results you had before deduplicating (and after deduplication) as this is something you will need to document in the PRISMA Flowchart. You will need to record:

• the number of results found in each database
• the total number of results from all databases together
• how many duplicates were detected from the total
• how many unique references remained after duplicates were removed.

De-duplication tools

No reference management software product will reliably identify all duplicates. Some duplicates may be missed and you will have to remove these manually. You should double check the records for all identified duplicates to see if they are really are the same before removing them.

• EndNote is the most popular reference management tool for removing duplicates, particularly as it gives an option to remove in bulk. You can find instructions on how to remove duplicates in our EndNote, removing duplicates guide.

• RefWorks - please refer to the How do I organise and search my references?  section in our RefWorks guide.

• Zotero - please refer to the Duplicate detection section in the Zotero guide.

• Mendeley - If you are using Mendeley, this Mendeley support webpage provides a step by step guide for removing duplicates.

• Systematic review management tools - there are various review management tools like Covidence, that also have deduplication tools. However, there is debate on how accurate they are so it is recommended the best method at the current time to use reference management software such as EndNote to remove the duplicates.

When all duplicates have been identified and removed you can move onto Title and Abstract screening.

If you are now going to use Covidence for screening, your list of unique records should be exported from your chosen reference management software as a RIS file and imported into "Screening".