Wikipedia:Identifying reliable sources (medicine)

See also: Wikipedia:Reliable sources, Wikipedia:No original research and Wikipedia:Manual of Style (medicine-related articles).

Wikipedia's medical articles, while not a source of medical advice, are nonetheless an important health information resource. Therefore, it is vital that medical articles be based on reliable published sources. These guidelines supplement the general guidelines at Wikipedia:Reliable sources with specific attention to sources appropriate for medical and health-related articles. Ideal sources for such articles include general or systematic reviews in reputable medical journals, widely recognised standard textbooks written by experts in a field, or medical guidelines and position statements from nationally or internationally reputable expert bodies. It is also useful to reference seminal papers on a subject to document its history and provide context for the experts' conclusions.

See Wikipedia:Reliable sources/Noticeboard for queries about the reliability of particular sources or ask at relevant Wikiprojects such as Wikipedia talk:WikiProject Medicine or Wikipedia talk:WikiProject Pharmacology.

Definitions

Further information: [[:Primary, secondary, and tertiary sources]]

• A primary source in medicine is one where the authors directly participated in the research or documented their personal experiences. They examined the patients, injected the rats or filled the test tubes, or at least supervised those who did. Many, but not all, papers published in medical journals are primary sources.
• A secondary source in medicine summarizes one or more primary or secondary sources, usually to provide an overview of the current understanding of a medical topic. Review articles and specialist textbooks are examples of secondary sources, as are position statements and literature reviews by major health organizations. A good secondary source from a reputable publisher will be written by an expert in the field and be editorially or peer reviewed.
• A tertiary source usually summarizes secondary sources. Encyclopedias, including Wikipedia, are tertiary sources.

In general, Wikipedia's medical articles should be based upon published, reliable secondary sources whenever possible. Reliable primary sources can add greatly to a medical article, but must be used with care because of the potential for misuse. For that reason, edits that rely on primary sources should only make descriptive claims that can be checked by anyone without specialist knowledge. Where primary sources are cited, they should be presented in a manner which hews closely to the interpretation given by the authors or by published, reliable secondary sources. Primary sources should not be cited in support of a conclusion which is not clearly adduced by the authors or by reliable secondary sources, as defined above (see Wikipedia:No original research).

Basic advice

Respect secondary sources

Individual primary sources should not be cited or juxtaposed so as to "debunk" or contradict the conclusions of reliable secondary sources, unless the primary source itself directly makes such a claim (see Wikipedia:No original synthesis). Controversies or areas of uncertainty in medicine should be illustrated with reliable secondary sources describing the varying viewpoints. The use and presentation of primary sources should also respect Wikipedia's policies on undue weight; that is, primary sources favoring a minoritarian opinion should not be aggregated or presented devoid of context in such a way as to undermine proportionate representation of expert opinion in a field.

Summarize scientific consensus

Scientific journals are the best place to find primary source articles about experiments, including medical studies. Any serious scientific journal is peer-reviewed. Be careful of material in a journal that is not peer-reviewed reporting material in a different field. (See the Marty Rimm and Sokal affairs.)

The fact that a statement is published in a refereed journal does not make it true. Even a well-designed experiment or study can produce flawed results or fall victim to deliberate fraud. (See the Retracted article on neurotoxicity of ecstasy and the Schön affair.)

Neutrality and no original research policies demand that we present the prevailing medical or scientific consensus, which can be found in recent, authoritative review articles or textbooks and some forms of monographs. Although significant-minority views are welcome in Wikipedia, such views must be presented in the context of their acceptance by experts in the field. The views of tiny minorities need not be reported. (See Wikipedia:Neutral Point of View.)

Make readers aware of any uncertainty or controversy. A well-referenced article will point to specific journal articles or specific theories proposed by specific researchers.

Assess evidence quality

Several systems exist for assessing the quality of available evidence on medical subjects, and these should be kept in mind while assessing whether a particular viewpoint is a majority or minority one, and in deciding what constitutes evidence-based medicine.

Two of the most commonly used schemes are the US Agency for Healthcare Research and Quality one:

Class	Requirements
Ia	Evidence from meta-analysis of randomised controlled trials (RCTs)
Ib	Evidence from at least one RCT
IIa	Evidence from at least one well-designed controlled study without randomisation
IIb	Evidence from at least one other type of well-designed quasi-experimental study
III	Evidence from well-designed non-experimental descriptive studies, such as comparative studies, correlation studies, and case control studies
IV	Evidence from expert committee reports or opinions and/or clinical experience of respected authorities

And the slightly simpler NHS one:

Grade	Evidence	Description
A	Ia, Ib	Requires at least one RCT as part of the body of literature of overall good quality and consistency addressing the specific recommendation
B	IIa, IIb, III	Requires availability of well-conducted clinical studies but no RCTs on the topic of recommendation
C	IV	Requires evidence from expert committee reports or opinions and/or clinical experience of respected authorities. Indicates absence of directly applicable studies of good quality.

Case reports, whether in the popular press or a peer-reviewed medical journal, are a form of anecdote and generally fall below the minimum requirements of either scheme. Sources for evaluating health-care media coverage include the review websites Behind the Headlines, Health News Review[1], and Media Doctor, along with specialized academic journals such as the Journal of Health Communication; reviews can also appear in the American Journal of Public Health, the Columbia Journalism Review, the Bad Science column in The Guardian, and others.

Use up-to-date evidence

Here are some rules of thumb for keeping an article up-to-date while maintaining the more-important goal of reliability. These guidelines are appropriate for actively-researched areas with many primary sources and several reviews, and may need to be relaxed in areas where little progress is being made and few reviews are being published.

• Look for reviews published in the last five years or so, preferably in the last two or three years. The range of reviews examined should be wide enough to catch at least one full review cycle, containing newer reviews written and published in the light of older ones and of more-recent primary studies.
• Within this range, things can be tricky. Although the most-recent reviews include later research results, do not automatically give more weight to the review that happens to have been published most recently, as this is recentism.
• Prefer recent reviews to older primary sources on the same topic. If recent reviews don't mention an older primary source, the older source is dubious. Conversely, an older primary source that is seminal, replicated, and often-cited in reviews is notable in its own right and can be mentioned in the main text in a context established by reviews. For example, Genetics might mention Darwin's 1859 book On the Origin of Species as part of a discussion supported by recent reviews.

These are just rules of thumb. There are exceptions:

• History sections often cite older work, for obvious reasons.
• Cochrane Library reviews are generally of high quality and are routinely maintained even if their initial publication dates fall outside the above window.

Periodicals

Periodicals include newspapers, magazines and journals. The latest research is usually published here first. Archives provide access to earlier research.

Medical journals

These are a natural choice as a source for up-to-date information for medical articles. They contain a mixture of primary and secondary sources, as well as less technical material such as biographies. Although almost all such material will count as a reliable source, not all the material is equally useful.

The 2003 Brandon/Hill selected list includes 141 journals suitable for a small medical library. Although this list is no longer maintained, the listed journals are of high quality.

Core journals

Impact factor is a crude guideline to a journal's authority. If the articles in the top journals tend to be cited most often by other expert authors, then it is not a bad idea to do likewise on Wikipedia. The core general medical journals include:

• New England Journal of Medicine
• The Lancet
• Journal of the American Medical Association (JAMA)
• Annals of Internal Medicine
• British Medical Journal (BMJ)
• Canadian Medical Association Journal

Core basic science and biology journals include:

• Science
• Cell
• Nature

Article type

Journal articles come in many types: original research, reviews, editorials, book reviews, correspondence, biographies and eulogies. Research papers are primary sources; although they normally contain previous-work sections that are secondary sources, these sections are typically less reliable than reviews. A general narrative review of a subject by an expert in the field makes a good secondary source that can be used to cover various aspects of a subject within a Wikipedia article. Such reviews typically contain no original research but can make interpretations and draw conclusions from primary sources that no Wikipedia editor would be allowed to do. A systematic review uses a reproducible methodology to select primary studies meeting an explicit criteria in order to answer a specific question. Such reviews should be more reliable, accurate and less prone to bias than a narrative review. However, a systematic review's focus on answering one question limits its usage as a source on Wikipedia.

Popular press

The popular press is generally not a reliable source for science and medicine information in articles. Most news articles fail to discuss important issues such as evidence quality, costs, and risks versus benefits. Articles in newspapers and popular magazines generally lack the context to judge experimental results. They tend to overemphasize the certainty of any result, for instance presenting a new experimental medicine as the "discovery of the cure" of a disease, or an every-day substance as the "cause" of some dreaded disease. Newspapers and magazines frequently publish articles about scientific results before those results have been peer-reviewed or reproduced by other experimenters. Such articles may be based uncritically on a press release, which can be a biased source. They also tend neither to report adequately on the scientific methodology and the experimental error, nor to express risk in meaningful terms.

A news article should not be used as a sole source for a medical fact or figure. Editors are encouraged to seek out the scholarly research behind the news story. One possibility is to cite a higher-quality source along with a more-accessible popular source, for example with the "laysummary=" parameter of the Cite journal template.

On the other hand, the high-quality popular press can be a good source for social, biographical, current-affairs and historical information in a medical article. For example, popular science magazines such as New Scientist and Scientific American are not peer reviewed but sometimes feature articles that explain medical subjects in plain English. As the quality of press coverage of medicine ranges from excellent to irresponsible, common sense and the general guidelines presented in the verifiability policy and general reliable sources guideline should be considered in determining whether a popular press source is suitable for these purposes.

Books

Medical textbooks published by the academic press are an excellent secondary source. Ensure the book is up-to-date, unless a historical perspective is required. Doody's maintains a list of core health sciences books, which is available only to subscribers.

Popular science and medicine books are usually tertiary sources, but there are exceptions. Self-published or books published by vanity presses are generally not subject to any form of independent fact-checking or peer review and may not be reliable sources.

Online

Reliable references

• OMIM provides a lot of useful info with regards to genetic diseases.
• eMedicine is a comprehensive and reliable source.
• WhoNamedIt is an excellent reference for eponyms in medicine.
• UpToDate is an excellent resource but only available to subscribers and at institutions.

Background reading

• MedlinePlus has encyclopedic content in plain English from the NIH.
• Diseases Database.
• SUNY Downstate Medical Center has an excellent set of online anatomic preparations.
• Merck Manual Home and Professional edition

Search engines

• PubMed is a free search engine which accesses the MEDLINE database

See also

• Dispatches: Sources in biology and medicine. The Wikipedia Signpost (2008-06-30)
• Reliable source examples in physical sciences, mathematics and medicine
• Users’ Guides to the Medical Literature