Finding and merging duplicates
Duplicates are found by DOI, PMID and normalised titles. Exact groups merge in one click; likely ones are yours to judge.
The same study often comes back from several databases. Removing the copies before screening saves work and keeps the PRISMA counts right: the flow diagram reports how many records were removed as duplicates.
How duplicates are found
- Same DOI or same PMID: an exact duplicate.
- Same normalised title (case, punctuation and spacing ignored): an exact duplicate when the rest agrees.
- Similar titles and authors: a likely duplicate, such as a preprint and its published version, or a conference paper and its journal extension.
Resolving them
- Exact groups resolve in one click: Merge all exact groups.
- Likely groups are shown side by side with their differences highlighted. Keep one record and merge the others into it, or mark them as different studies.
When you keep a record, it fills its gaps from the others in the group (for example an abstract, a DOI or the page numbers that only one copy had), and the others are counted as removed duplicates. A removal can be undone; the pair is then remembered as distinct.
A preprint and its published version are the same study for a systematic review. Keep the published version when both are there.