Preprints, Peer Review, and Published Papers: How the Evidence Status Changes

Short answer: Before you share or act on a health claim, find out which stage the paper is at: preprint, journal-published, corrected, flagged with an expression of concern, or retracted. Each stage means something different about how far the findings have been checked. You can confirm the stage in a few minutes by looking up the paper in the journal record and in a database such as PubMed.

This article is an educational explainer prepared by the MedClinRes.org Editorial Team. It has not been peer reviewed or clinically reviewed, and it is not medical advice. Source checks were last completed on September 30, 2026.

Why the publication stage matters

A headline that says “a study found” can describe very different documents. Some have been examined by outside experts and edited by a journal. Others were posted online by the authors and have not been examined by anyone. The same paper can also move between stages over time, so a claim that was accurate last year may no longer be accurate now.

The status map: from preprint to corrected or retracted

Stage 1: Preprint

A preprint is a manuscript made public before journal peer review. The health-science server medRxiv states that preprints are preliminary reports not certified by peer review, should not be relied on to guide clinical practice or health-related behavior, and should not be reported in news media as established information.
medRxiv also notes that it does not edit or typeset manuscripts before posting.
Preprints can have several versions. medRxiv supports version-specific links, so record which version you read.

Stage 2: Preprint with public reviews

Some journals and independent review services make peer reviews public, and you can access them from the medRxiv dashboard.
Read the reviews themselves. Their presence shows that people have examined the work, but on its own it does not tell you the paper was accepted.

Stage 3: Published in a journal

In traditional peer review, journal editors take advice from expert referees who assess the paper and may identify weaknesses in its assumptions, methods and conclusions.
The published version can differ from the preprint. In one analysis of COVID-19 papers, 124 of 182 cited preprints had later been published in a peer-reviewed journal, and the title, data or conclusion differed for nearly half of them.
Peer review is a check, not a guarantee. A 2020 review of preprints in medicine notes that peer review is imperfect and does not always ensure accurate results.

Stage 4: Corrected

PubMed Central (PMC) requires a published correction notice that specifies the exact nature of the error.
If a journal republishes a corrected article, PMC keeps the original and links to the update.
In PubMed, the original record carries an “Erratum in” line that links to the notice.
Since October 2016, NLM has treated partial retractions as published errata, so an “Erratum in” line can sometimes signal something bigger than a typo. Read the notice itself.

Stage 5: Expression of concern

An expression of concern is an editor's notice that flags possible problems without retracting or correcting the article.
COPE's retraction guideline advises editors to publish one when a determination is delayed.
PubMed links the article to its notice with an “Expression of concern in” line. Treat the findings as uncertain until the journal resolves it.

Stage 6: Retracted

PMC describes retraction as the response to serious problems such as misconduct, plagiarism, pervasive error or unsubstantiated data. The notice should state why the article is invalid.
Retracted articles are not deleted. PMC marks them boldly and links to the notice, and COPE says retracted articles should be unmistakably identified in all online sources.
PubMed assigns the publication type “Retracted Publication”.
A retracted paper can still be found and read, so finding it online says nothing about whether it is valid.

How to verify the stage in five steps

Identify the exact record. Write down the full title, journal or server, DOI, and PMID or PMCID if there is one. Do not rely on a news summary.
Open the journal or server page. Look for the article type, the dates, any version history, and any banner or notice.
Check the database record. In PubMed, look at the publication types and for “Erratum in”, “Expression of concern in”, or “Retracted Publication” lines.
Check PMC if the full text is there. PMC is a full-text archive, not a citation database like PubMed, and its open-access subset also includes preprints. Being in PMC does not by itself tell you the stage.
Search the title again for a later version. Preprint servers link to published versions, but a 2023 study of preprint matching notes that such links can miss published works that changed significantly from the preprint.

What this can and cannot tell you

The stage tells you how much checking a paper has had. It does not tell you the result is true or that it applies to you.
A journal's stated process is worth reading, but its label is not proof that the process is sound. Check whether it is a known, indexed publication.
If you cannot find a notice, that is not proof none exists. Databases can lag behind journals.

Who should seek professional advice?

Do not start, stop, or change a medication, supplement, or treatment because of a preprint or a single study. Talk with a licensed clinician or pharmacist who knows your history. If you are a journalist, clinician or researcher relaying a finding, state its stage in plain words: “preprint, not peer reviewed” or “retracted in [year]”.

What to do next

Before sharing a claim, run the five steps above and note the stage next to the citation.
If you find an error in our work, our Corrections Policy explains how to report it.
To see how we work and what we do not claim, read our Editorial Standards and Editorial Team and Review Process pages, and our Medical Disclaimer.