Research guide7 min read
Study reader
DOI
Enter the DOI of any published study to see its title, journal and year, its type according to the U.S. National Library of Medicine’s publication types (such as randomized trial or systematic review), its approximate place in the evidence pyramid, and whether it has been retracted, corrected or flagged with an expression of concern.
The reader connects to two public services: Crossref, which holds Retraction Watch records of retraction notices and is updated every working day, and Europe PMC, which returns the publication types registered for an article using NLM classification names. Only the DOI you type is sent to them, and only after you press the "Check" button.
The classification here describes the type of the article, not its quality: a poorly conducted randomised trial remains a "randomised trial" in the classification, and confidence in its evidence may be downgraded in the GRADE approach because of risk of bias or imprecision. The reader does not judge whether a study's results are valid, and the absence of a retraction notice is no substitute for reading the study itself or asking a specialist.
Check a study by its DOI
When you press “Check”, your browser sends only the DOI to two public research services: Crossref (api.crossref.org) and Europe PMC (www.ebi.ac.uk). Nothing else is sent, and nothing passes through or is stored on the Medi.kharousi server.
What the reader does
The reader combines two sources: the publication types that Europe PMC returns for the article, which use the NLM "publication types" classification names (such as Randomized Controlled Trial, Meta-Analysis and Retracted Publication), and the update notices linked to the DOI in Crossref, including Retraction Watch data.
The Retraction Watch database has been publicly available through Crossref since it acquired it in September 2023, and is updated every working day.
Reading the result
"Retracted" banner: the article's retraction is recorded in Crossref/Retraction Watch or it is classified "Retracted Publication"; do not rely on its results.
"Expression of concern" banner: the editor has flagged a problem with the integrity of the article, and the investigation may end in retraction.
"Correction" notice: a correction has been issued for an error in the article; read the correction together with the article.
"Preprint": not yet peer reviewed, and its results and conclusions may change.
The study's position in the evidence pyramid is inferred from the publication type alone, as a starting point for reading and not as a judgement of quality.
How to use it
Type the DOI as it appears in the study (starting with 10., for example 10.1000/xyz123), or paste the full doi.org link, then press "Check".
When you press the button, your browser sends the DOI alone directly to Crossref and Europe PMC, and the request does not pass through the Medi.kharousi server or get stored there; and as with any request over the internet, technical information such as your device's IP address reaches these two services.
Limits of the reader
If no publication type appears for the article, the reader does not know its type, and this means nothing about its quality; it only means the classification is not available in the source.
The data on corrections and expressions of concern in Retraction Watch are less comprehensive than the retraction data, and some records may lack DOI identifiers.
The reader classifies the type of the article and does not assess its quality or the validity of its results; and in GRADE, confidence may be downgraded even for randomised trial evidence.
Titles and journal names are shown as they appear in the source, usually in English.
Common questions
What should I do if I find that a study I heard about has been retracted?
Do not rely on its results. And remember that the NLM does not distinguish in its linking between retraction for an honest error and retraction for misconduct; if the study concerns your treatment, discuss the matter with your doctor.4
Does "Review" mean a systematic review?
No. The publication type "Review" means an article based on examining what has been published on a subject and its comprehensiveness may vary, whereas a "Systematic Review" follows explicit conditions and methods to identify and assess all eligible evidence and reduce bias.2
Questions for your doctor
- I read a study about a treatment that concerns me; is it the kind on which a treatment decision is based?
- Is there more recent or stronger evidence than this study?
References
- 1Europe PMC. Europe PMC. europepmc.org/Educational & historical references · Accessed 2026-10-08
- 2U.S. National Library of Medicine. Publication Characteristics (Publication Types) with Scope Notes. www.nlm.nih.gov/mesh/pubtypes.htmlHealth agencies & guidelines · Accessed 2026-10-08
- 3Crossref. Retraction Watch (Crossref documentation). www.crossref.org/documentation/retrieve-metadata/retraction-watch/Educational & historical references · Accessed 2026-10-08
- 4U.S. National Library of Medicine. Errata, Retractions, and Other Linked Citations in PubMed. www.nlm.nih.gov/bsd/policy/errata.htmlHealth agencies & guidelines · Accessed 2026-10-08
- 5PubMed Central (NLM). NIH Preprint Pilot. pmc.ncbi.nlm.nih.gov/about/nihpreprints/Health agencies & guidelines · Accessed 2026-10-08
- 6CDC (ACIP). ACIP GRADE Handbook — Chapter 7: GRADE Criteria Determining Certainty of Evidence. www.cdc.gov/acip-grade-handbook/hcp/chapter-7-grade-criteria-determining-certainty-of-evidence/index.htmlHealth agencies & guidelines · Accessed 2026-10-08
Review status: Edited content · Last updated:
Change log
- — Page created.
Educational content only — no diagnosis, and no substitute for a clinician.