How are Medline articles added to Embase and why can they be deleted?

Records can be part of different collections:

• Embase unique – Items published in journals covered by Embase but not part of the Medline collection.
• MEDLINE unique – Items published in journals covered in Medline that are not part of the Embase unique journals collection
• Embase/MEDLINE overlap – Items published in journals that are both part of the Embase journal collection and the MEDLINE journal collection

1. What happens if there is an overlap between Embase and MEDLINE records

   For the overlap collection it is important to keep in mind that the Embase record is preferred over the MEDLINE record.

   As there is overlap, a deduplication process is needed to prevent duplicates on the Embase.com platform.

   In case an Embase record is created and delivered prior to the creation and delivery of the corresponding MEDLINE record, the MEDLINE record will not be delivered. Instead, the Embase record will be delivered again as an update and will include the MEDLINE PMID of the MEDLINE record. In this way Embase.com will have only one record on its platform, containing the MEDLINE PMID.

   In case the MEDLINE record is created and delivered prior to the creation and delivery of the corresponding Embase record, both records are delivered as new. When the Embase record is delivered, it will contain both the associated PUI and the MEDLINE PMID. To prevent duplicates on Embase.com, also a deletion happens for the corresponding MEDLINE record followed by the new delivery of the new record.

2. Disappearing records: Quarterly MEDLINE clean-up

   Occasionally Pubmed does a clean-up of records on its platform which also applies to the MEDLINE collection we receive. As Embase.com wants to be in sync with Pubmed, MEDLINE records deleted from the PubMed platform also need to be deleted from the Embase.com platform. To cater for this, a deletion occurs every three months with an average of 6000 records divided over two days.