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Systematic Reviews, Scoping Reviews, and other Knowledge Syntheses

Updating the database searches

There are different methods that you can use to update your searches, and they are usually database-specific. What you are trying to do is avoid screening the same records all over again.

If you have access to Covidence (not yet available at McGill as an institutional subscription, but available through subscription or through most other Canadian universities with medical schools), you can simply import all the records generated by the new/updated searches, and Covidence will remove records that have already been uploaded

Another method is to restrict records to those entered into the database on or after the date you last ran the search (note: this is NOT the publication date, this is the date the record was added to the database, and this date field is not available in all databases).

This can be done in PubMed, MEDLINE (Ovid), Embase (Ovid), Scopus, CINAHL (EBSCOhost), APA PsycInfo (Ovid), and Web of Science Core Collection (as well as others), but unfortunately the entry date is not available as a search field in all databases.

Please note: The field codes are subject to change and we strongly suggest checking the database information, particularly at the beginning of a new year, when indexing changes are more likely to occur. Please also let us know if you identify issues with these codes. This table was last updated September 1, 2022 (CINAHL).

Many thanks to those who reach out to let us know when there are issues or corrections needed!


Alternative method to retrieve new records only, using EndNote

General method

You can also merge old and new records for each database search into one library and remove records that appear in both the old and new libraries (e.g., in databases that do not have a field referring to the date the record was added to the database):

  1. Place the updated/new records in one EndNote group and the old records in a separate EndNote group (to allow you to keep track of what old records are not being removed as duplicates--this will be useful later)
  2. Check the updated/new records for duplicates within that set. Always make sure the new group of records does not contain duplicates because you will be removing all copies of duplicate records and you don't want to remove all copies of duplicate records if they're only in the new set!
  3. Use the find duplicates feature of EndNote to search for duplicates; Make sure to compare the author/title/secondary title/volume/pages fields, for example, then, after checking to make sure they are true duplicates (e.g., no blank fields in the record causing false duplicates to be picked up): Highlight (Windows: Ctrl-A; Mac: Cmd-A) all the records in the Duplicate References folder and send to the trash -- this will delete the new copy of the record and the old copy of the record
  4. You will hopefully notice that the number in the group of old records will be very low, if the removal of old and new copies of the same record has worked; that said, there may be some stragglers:
    • You can then highlight the leftover records in the old record group and go back to All References and sort by title (this assumes the old and new records have titles starting with the same words) to see if there are any new copies of the old records that your search for duplicates missed: Delete both copies of any leftover duplicates you find
    • There may be some leftover records in the old record group that do not have duplicates in the new record group: You can delete those because you should have already screened them prior to the update

Ovid MEDLINE or PubMed

Here is another example of how you can restrict Ovid MEDLINE or PubMed records to only those records that you had not previously screened from the original MEDLINE search:

  • Be sure to always export the complete reference from Ovid: This will ensure the unique identifier (aka accession number) is included in your references. To check if you have that info in your records, open your EndNote library, double-click on a record, and in the Summary or Edit tab, check the accession number field contains the unique identifier
  • You should have a saved copy of the MEDLINE records from the previously run search in your files (this will often be in an EndNote library but you may also have saved the records in a .ris file etc.; the latter would have to be imported into an EndNote library) -- make sure it also contains the unique identifier in the accession number field
  • You can merge the previous EndNote library of MEDLINE records and the new EndNote library of MEDLINE records (be sure to use a deduplicated version of the new EndNote library before starting the steps below, otherwise you may end up removing, e.g., two copies of a record that are only in the new library)
    • Using an empty EndNote library, import the records from the original MEDLINE search, place them in their own group called, e.g., OLD, and go to Library > Change/Move/Copy Fields > Move/Copy Fields tab to Move Field From: Accession Number To: Label in the record (it's okay to replace the entire field as long as you weren't using the Label field for something else).
      • Why do this? Because the option to detect Duplicates (Edit (Windows) or EndNote (Mac) menu > Preferences) in EndNote only allows a limited set of reference fields to be compared for matches, and Label is one of those fields. The accession number is arguably a more precise field to use to identify record matches in MEDLINE than comparing author/year/title/secondary title/volume/pages, for example
    • In the same EndNote library, import the records from the new MEDLINE search, place them in their own group, e.g., NEW, and go to Library > Change/Move/Copy Fields > Move/Copy Fields tab to Move field From: Accession Number To: Label in the record (it's okay to replace the entire field as long as you weren't using the Label field for something else).Move/Copy fields tab, select Move Field, From Accession Number to Label
      • In the new group only, be sure to remove duplicate records from this group: Go to Edit > Preferences > Duplicates: Check off the label field for comparison, make sure you have only selected the new group of records (you can highlight the new records in the new group, just to be sure); go to References > Find Duplicates and get rid of any duplicate records (leaving one copy behind) showing up in the new group (this is to avoid deleting duplicate records that only appear in the new set of records, in case the record wasn't also in the original record set, given the next step)
    • In All References, with Edit > Preferences > Duplicates comparing the Label field only (to which you've moved the accession number), perform a Find Duplicates search: The duplicates will be placed in a Duplicate References folder: Highlight all the records in that folder and delete them
    • If there are still records left in the OLD MEDLINE group, you can Ctrl A to highlight them then return to All References and sort by title to see if any of them are also duplicates, then delete those (and any new duplicates) as you have already screened them


See also: Garner P, Hopewell S, Chandler J, MacLehose H, Akl EA, Beyene J, Chang S, Churchill R, Dearness K, Guyatt G, Lefebvre C, Liles B, Marshall R, Martínez García L, Mavergames C, Nasser M, Qaseem A, Sampson M, Soares-Weiser K, Takwoingi Y, Thabane L, Trivella M, Tugwell P, Welsh E, Wilson EC, Schünemann HJ. When and How to Update Systematic Reviews: Consensus and Checklist. BMJ. 2016;354. 10.1136/bmj.i3507

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