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This page documents an English Wikipedia content guideline. It is a generally accepted standard that editors should attempt to follow, though it is best treated with common sense and the occasional exception. Any substantive edit to this page should reflect consensus. When in doubt, discuss first on the talk page.

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This page in a nutshell: Ideal sources for biomedical articles include general or systematic reviews in reliable, third-party, published sources of 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.

Wikipedia guidelines
Content
Conflict of interest Do not copy sources Disambiguation Do not create hoaxes Patent nonsense Reliable sources User page
Article Inclusion
Notability
Classification
Subpages Cats, lists, templates Lists Categories
Editing
Be bold Build the web Edit summary Article size
Discussion
Talk page guidelines Sign on talk pages
Behavior
Etiquette Assume good faith Do not disrupt Wikipedia to illustrate a point Do not bite the newcomers Do not "game the system"
Style
Manual of Style See also policies

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.

Contents 1 Definitions 2 Basic advice 2.1 Respect secondary sources 2.2 Summarize scientific consensus 2.3 Assess evidence quality 2.4 Use up-to-date evidence 3 Search 4 Accessing sources 5 Citations as documentation 6 Biomedical journals 7 Popular press 8 See also 9 References

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 a range of secondary sources. General textbooks and encyclopedias 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 describe the conclusions of the source, and should describe these findings clearly so the edit can be checked by editors with no specialist knowledge. In particular, this description should follow closely to the interpretation of the data given by the authors, or by other reliable secondary sources. Primary sources should not be cited in support of a conclusion that is not clearly made 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 minority 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.

Search

Search engines are commonly used to find biomedical sources. Each engine has quirks, advantages, and disadvantages, and may not return the results that you need unless used carefully. It typically takes experience and practice to recognize when a search has not been effective; even if you find useful sources, you may have missed other sources that would have been more useful, or you may generate pages and pages of less-than-useful material. A good strategy for avoiding sole reliance on search engines is to find a few recent high-quality sources and follow their citations to see what your search engine missed. It can also be helpful to perform a plain web search rather than one of scholarly articles only.

PubMed is an excellent starting point for locating peer-reviewed medical sources. It offers a free search engine for accessing the MEDLINE database of biomedical research articles offered by the National Library of Medicine at the U.S. National Institutes of Health. There are basic and advanced options for searching PubMed. Clicking on the "Review" tab will help you narrow your search to reviews. The "Limits" tab can let you further limit your search, for example, to meta-analyses or to freely-readable sources. Although PubMed is a comprehensive database, many of its indexed journals restrict online access. An additional site, PubMed Central, provides free access to full text; this is often not the official published version but is a peer-reviewed manuscript that is substantially the same but lacks minor copyediting by the publisher.¹

Other useful search engines include:

• The Cochrane Library contains a database of systematic reviews and meta-analyses, and is a key resource in evidence-based medicine. Its reviews are generally considered to be of very high quality.

• Google Scholar covers all scholarly sources. It is useful not only as a sanity check for PubMed searches, but also to cover topics outside PubMed's core purview, such as the sociological or cultural aspects of medicine.

• Google Books can also be quite useful for medical searches: it can let readers peek at a few sentences in books even when full access is not granted, and can help editors find reliable sources quickly, either by looking at the book's references or by citing the book itself.

• EMBASE is a high-quality index that often generates better results than PubMed. Unfortunately, it is proprietary and requires a subscription.

• CINAHL is a proprietary index on nursing and allied health care.

Accessing sources

A Wikipedia article should cite the best and most-reliable sources regardless of whether they require a fee or a subscription. When all else is equal, it is better to cite a source whose full text is freely readable, so that your readers can follow the link to the source. Some high-quality journals, such as JAMA, publish a few freely-readable articles even though most are not free. A few high-quality journals, such as PLoS Medicine, publish only freely-readable sources. Also, a few sources are in the public domain; these include many U.S. government publications, such as the Morbidity and Mortality Weekly Report of the Centers for Disease Control and Prevention.

When searching for sources, it is wise to skim-read everything available, including abstracts of papers you can't fully access, and use that to get a feel for what reliable sources are saying. However, when it comes to actually writing a Wikipedia article, it is generally not a good idea to cite a source after reading only its abstract, as the abstract necessarily presents a stripped-down version of the conclusions and omits the background that can be crucial for understanding exactly what the source says. You may need to visit a medical library to access the full text, or ask somebody at the WikiProject Resource Exchange to either provide you with a copy or read the source for you and summarize what it says; if neither is possible, you may need to settle for using a lower-impact source or even just an abstract.

Citations as documentation

Citations should document precisely how to access sources. Normally, medical citations should contain a PubMed identifier (PMID). It is good practice to also supply a digital object identifier (DOI) if available. A common practice is to supply a uniform resource locator (URL) to a source if and only if its full text is freely readable. If the {{Cite journal}} template is used, all this information can be supplied with the "pmid=", "doi=", and "url=" parameters, respectively. It is also helpful to mention whether a source is also available on PubMed Central; with {{Cite journal}} this can be done with the "pmc=" parameter. For example:

{{cite journal |author= Bannen RM, Suresh V, Phillips GN Jr, Wright SJ, Mitchell JC |title= Optimal design of thermally stable proteins |journal=Bioinformatics |volume=24 |issue=20 |pages=2339–43 |year=2008 |pmid=18723523 |pmc=2562006 |doi=10.1093/bioinformatics/btn450 |url=http://bioinformatics.oxfordjournals.org/cgi/content/full/24/20/2339}}

produces this:

Bannen RM, Suresh V, Phillips GN Jr, Wright SJ, Mitchell JC (2008). "Optimal design of thermally stable proteins". Bioinformatics 24 (20): 2339–43. doi:10.1093/bioinformatics/btn450. PMID 18723523. PMC: 2562006, http://bioinformatics.oxfordjournals.org/cgi/content/full/24/20/2339. 

If a source is available in both HTML and some other form, normally the HTML form should be linked to, as it is the most likely to work on a wide variety of browers.

Biomedical journals

As mentioned above, the biomedical literature contains two major types of sources: primary publications describe novel research for the first time, and review articles summarize and integrate a topic of research into an overall view. In medicine, primary sources include clinical trials, which test new treatments; secondary sources include meta-analyses that bring together the results from many clinical trials and attempt to arrive at an overall view of how well a treatment works. It is usually best to use reviews and meta-analyses where possible, as these give a balanced and general perspective of a topic, and are usually easier to understand!

Peer-reviewed medical journals 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. 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.² However, a systematic review's focus on answering one question limits its usage as a source on Wikipedia.

The 2003 Brandon/Hill selected list includes 141 journals suitable for a small medical library.³ Although this list is no longer maintained, the listed journals are of high quality. The core general medical journals include the New England Journal of Medicine, The Lancet, Journal of the American Medical Association (JAMA), Annals of Internal Medicine, British Medical Journal (BMJ), and Canadian Medical Association Journal. Core basic science and biology journals include Science, Cell, and Nature.

Medical textbooks published by the academic press are excellent secondary sources. 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.⁴

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.⁵ 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 {{Cite journal}}.

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.

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.

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

References

Wikipedia content modification information:

• This page was last modified on 31 October 2008, at 19:40.

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