The tale of two ethical or unethical duplicate publications in one or more journals: Inclusion or exclusion decisions in a systematic review

Funny game, publish or perish. It pushes people to cut the sausage into salami, co-submit to several journals, or co-publish in more than one journal.

During De-Duplication Stage

One of the information professionals found the same paper but in two different journals during de-duplication. Should we remove one of them as a duplicate?

What is a duplicate record? A duplicate bibliographic record in a systematic review context is a record that has as same as or very similar bibliographic information to another record among your search results or in your database. Bibliographic information is authors, publication year, the title of records, source/journal, volume, issues, page numbers, DOI, and so on. Since records in all databases are not always keeping their records up-to-date, a duplicate record is not always an exact match to another record because it may contain publication year from the pre-pagination version — when the journal publishes the accepted paper early and assigns it to a journal issue with page numbers 1–5 years later — or when databases miss some of the bibliographic information. For more information, please see typology of duplicate records.

While there are many automated and semi-automated methods to find these duplicates, there is no method with 100% sensitivity and specificity to do the de-duplication for you without causing paranoia of what if the machine is wrong.

One of the strange cases you may face is finding the same paper published in two or more journals. Since the sources/journals of the papers are different, they are not considered duplication, and we should keep them as unique records during the de-duplication. Sometimes, the same title may appear in the same journal and still, the two records may not be duplicates.

Post-De-Duplication Stage

Scenario 1: Unethical Co-Publication of the Same Paper in Different Journals — If the ‘same’ paper is published in two journals without the journals knowing about it, it is our responsibility to inform their editors in chief. If they are unaware, both journals — assuming that they are not predatory journals/publishers — retract the paper and remove it from their website and add a retraction note on the paper’s place. These papers may be excluded based on eligibility criteria during the record screening stage. They will be excluded during the report screening stage for violating publication ethics even if they meet the inclusion criteria. I can discuss the reasons why this happens in another post.

Scenario 2: Ethical Co-Publication of the Same Paper in Different Journals— The paper is a statement published on two or several journals simultaneously with the information and agreement of all journals. Examples of such statements are PRISMA and CONSORT reporting guidelines that have been published at the same time in several journals. The review team deal with these two as reports of one study if they make it to the report screening stage. It is ethical to publish such statements in several journals to inform a wider audience as long as all journals are aware and agree.

Scenario 3: Ethical Co-Publication of the Same Paper in the Same or Different Journals — If a paper has historical importance or becomes important after several years — so-called “Sleeping Beauty” like all my papers :) — it is possible that the same or a different journal re-publish with a new publication year and note. This happens when a prediction becomes true, an important fact changes or requires re-highlighting, a famous author passes away, or other reasons — a master’s thesis for your student. The review team deal with these two as reports of one study if they make it to the report screening stage.

Scenario 4: Salami Publication of the Same Paper in the Same Journal — it happens for several reasons:

  1. The same journal that has published the abstracts of a conference also published the full paper of the same abstract.
  2. The journal publishes the paper in 2 or 3 parts because they think it is too long.
  3. The journal asks someone to write a review paper and publish the updated version of this review every year or every few years.

While the title of the paper and the journal are the same, the content and sometimes the publication years are different. That’s when you get the two records with the same title, journal name, even year BUT different page numbers. These records will be kept during de-duplication, and The review team will deal with these two as reports of one study if they make it to the report screening stage.

Scenario 5: Salami Publications of the Same Study in the Same or Different JournalBoth papers have the same or similar title/abstract but present different results. Then you keep both as reports of the same study. The review team deal with these two as reports of one study if they include or exclude them during the report screening stage.

Scenario 6: Database Errors — the databases that index the papers are not always perfect. They can make an error in indexing the fields and mess up the record with wrong information or cause true or false duplication. More investigation and contacting the database to correct the error are required in such cases. I don’t know any caring information professional who has not contacted the databases at least once.


It is important to stay neutral at first look and not jump to conclusions. There are some types of duplicate records that the automation will have real difficulty detecting or investigating. I wrote this blog to emphasise again the importance of professionalism in de-duplication and awakening those who think removing the duplicates is clicking two buttons in EndNote and then clicking delete from the keyboard. It only takes a few seconds, some may claim!

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