Error 1: Confusing PubMed with MEDLINE

A frequent error in systematic reviews and research reports is describing search sources as "PubMed/MEDLINE," "MEDLINE via PubMed," or simply "MEDLINE" when the search was actually run in PubMed. This terminology is imprecise and should be avoided.

The key distinction: database vs. platform

A database is a collection of indexed content (e.g., citations, abstracts). A platform (or interface) is the search tool used to access one or more databases. These are not interchangeable terms, and conflating them creates ambiguity about what was actually searched.

MEDLINE is a database — the most widely searched biomedical database in the world.

PubMed is a free platform that provides access to MEDLINE content, plus additional non-MEDLINE content (e.g., PubMed-only records, PMC articles, ahead-of-print citations). PubMed is not itself a database — it's an interface.

Other platforms also provide access to MEDLINE, such as Ovid MEDLINE, ProQuest, and Web of Science. Ovid's MEDLINE All, for example, gives access to essentially the same underlying MEDLINE content as PubMed, with some added search features.

What this means for reporting your search:

• If you searched only PubMed, report it as PubMed — do not also write "MEDLINE" or "PubMed/MEDLINE," since this is redundant and confusing (PubMed already includes MEDLINE content).

• If you searched MEDLINE via Ovid (or another platform), name the platform explicitly — e.g., "MEDLINE (Ovid)" — since MEDLINE alone doesn't tell the reader how it was accessed.

• Never write "MEDLINE" alone as if it were a standalone searchable interface — it isn't one; it's always accessed through a platform.

Quick rule of thumb: always report database + platform together when it's not PubMed (e.g., "MEDLINE via Ovid"), and simply report "PubMed" when that's the platform you used — no need to append "MEDLINE."

Error 2: Describing PRISMA as Methodology Guidance

PRISMA stands for "Preferred Reporting Items for Systematic Reviews and Meta-Analyses." Authors frequently write phrases like "we conducted our review according to PRISMA guidelines" or "the scoping review was performed according to PRISMA guidelines." A recent published example of this can be seen here.

Why this is an error

PRISMA is a reporting tool, not a methodological one. It provides a checklist and flow diagram to help authors transparently report what they did in a systematic review — it does not tell you how to conduct one (i.e., it does not guide decisions about search strategy design, study selection processes, risk-of-bias assessment methods, or data synthesis approaches). Saying a review was "conducted according to PRISMA" misrepresents its purpose and blurs the line between conducting research and reporting it.

How to phrase it correctly

Instead, describe PRISMA as a reporting framework applied to how the review's process and findings are presented. For example:

"We reported the decisions regarding inclusion and exclusion in accordance with the PRISMA statement." (Moher et al., 2015)

Or more generally:

"This review is reported in accordance with the PRISMA 2020 statement."

Quick rule of thumb: Use PRISMA when describing how you wrote up and presented your review and not how you carried it out. For actual methodological guidance on conducting systematic reviews, refer instead to sources like the Cochrane Handbook or JBI Manual.

Error 3: Equating Grey Literature with Unpublished Literature

Some librarians and researchers treat "grey literature" and "unpublished literature" as synonyms. This is inaccurate because the two terms are related but not equivalent.

Grey literature refers to material and research produced by organizations outside traditional commercial or academic publishing and distribution channels. This includes items such as reports, theses, conference proceedings, government documents, and working papers, many of which may actually be formally issued or distributed by their producing organization, just not through conventional publishing channels.

Unpublished literature, by contrast, refers specifically to material that has not been formally published or peer-reviewed at all (e.g., data sitting in a drawer, a manuscript never submitted anywhere, personal communications).

The relationship between the two:

Unpublished literature can be considered a subset of grey literature, but grey literature is a much broader category. Grey literature encompasses many materials that are published or publicly disseminated by their originating body (e.g., a WHO technical report, a government policy brief, a university dissertation) and they simply bypass traditional commercial/academic publishers. Calling all grey literature "unpublished" ignores this distinction and can misrepresent the nature and credibility of these sources in a systematic review.

Quick rule of thumb: All unpublished literature is grey literature, but not all grey literature is unpublished. When describing your search of grey literature sources, avoid the blanket term "unpublished" unless the specific material truly has not been issued or disseminated in any form.

(Source: Grey literature – Wikipedia)