Quick answer: search three databases for a literature review and the same paper shows up in each — formatted just differently enough that nothing matches automatically. The clean fix is to export everything, dedup with a purpose-built tool, and keep source tags so your PRISMA counts stay auditable. Here’s the workflow.
Anyone running a serious review knows the dirty secret: comprehensiveness means duplicates, and lots of them. A public-health team recently imported 4,212 records from four databases — and about a third were duplicates. Left unmanaged, they inflate your screening load and distort your counts.
The workflow
- Export in RIS from each database separately.
- One collection per source in your reference manager (Zotero works well) — source tagging is what makes your PRISMA numbers auditable later.
- Run the deduplicator. Zotero’s built-in *Duplicate Items* detector compares titles, DOIs, and ISBNs and is the most accessible option most researchers already have installed. For audit-grade accuracy, ASySD (free, from the University of Edinburgh) tested at 0.95–0.99 sensitivity across datasets up to 80,000 citations.
- Merge to the richest record — when you collapse a cluster, keep the master with the fullest metadata.
- Record the counts straight into your PRISMA flow diagram.
That public-health team’s 4,212 records collapsed to 2,790 unique in under an hour, source tags intact.
One pro move: maintain a master “Screened” library with decision tags. Each quarter, dedup new results against it — anything flagged as a duplicate is something you’ve already screened. Quarterly review time drops from days to hours.
Full profiles of Zotero, ASySD, and the systematic-review toolkit are in the directory.
Try it: run *Duplicate Items* on your current reference library right now. How many duplicates have been quietly inflating it?
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