Quality of References

Question

The medical sciences are evidence-based, and because it is a field in which wrong information can be harmful, it is important that questions and answers also be evidence-based. The quality of references matters, as validity varies widely - from internationally validated clinical guidelines to an individual's opinion blog.

This is a discussion of the strength of evidence that is accepted here. Please edit the answers, and add comments at the bottom if you want.

Here is a previous discussion that can be brought into this discussion: Permissibility of non-medical sources

Answer 1

Excellent Sources

Sources that provide information based on validated clinical decision rules, meta-analysis of high-quality studies, etc.

• International, national, state governmental health websites (e.g. WHO, NIH, CDC, USPSTF)
• Professional organizations (e.g. AHA, AAFP, ACOG)
• Journals (indexed at PubMed, National Institute for Health and Care Excellence (NICE), TRIP database; like AMJMED)
• systematic review sites: Cochrane Library, Campbell Collaboration

More examples can be found in the reliable sources list

Appropriate Sources for Common Knowledge

Sources that are trustworthy enough to use them as references for common knowledge:

• WebMD, Medscape, Mayo Clinic
• Wikipedia.org (if it is directly pertinent and you've looked at the reference supporting the specific information as sometimes it is wrong; prefer to use the references cited in Wikipedia directly)

Good Sources but not easily accessible, so use alternatives when possible:

• UpToDate: (a clinical resource commonly used, peer reviewed and evidence-based with extensive high quality resources; however, much of its content requires a rather pricey subscription. If possible, link to the references they use.)
• Primary literature articles behind pay walls

Poor Sources

Sources that are not verifiable by other users:

• Individuals' blogs (Note: if the site links to high quality resources, use those resources as your links instead of the blog)
• Family members
• "I know a doctor who..."
• "I am a doctor who..."
• "When this happened to me, I..."

Notes

• Clinical/professional education and experience does offer insight; however, but no one here can be validated as a professional. Therefore other evidence is always preferred. However, under some circumstances a professional can refer to experience if (1) it's not the primary source of evidence and (2) if prefaced appropriately "In my clinical experience, I have never seen this manifested..."

• Concerning junk science; although it should be more common on the bottom of our list of quality sources than near the top, no journal or book or study represents the ultimate truth. Check the questions and aims, the methodology, the statistics, results and conclusions of your sources. Do not trust blindly everything that turns up on PubMed. Quality comes even there in a range of colours.

• Science is no belief system but a process. A single study is good but usually not enough to reach conclusive evidence. Check the age of these publications, look for contradictions, retractions or refutations, conflicting information or conflicts of interests. Use more than one source if possible and weigh the facts available to you. Do likewise with the answers you read here. Check the reasoning, the sources and the conclusions for their soundness. Then comment and vote.

Some help for reading, understanding and interpreting scientific and medical papers:

Trisha Greenhalgh: How to read a paper the basics of evidence-based medicine

Caroline De Brún & Nicola Pearce-Smith: Searching skills toolkit : finding the evidence

Iain K. Crombie: The pocket guide to critical appraisal : a handbook for health care professionals

Ben Yudkin: Critical reading : making sense of research papers in life sciences and medicine

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How to document sources

(extract from @LangLangC's now deleted answer)

The internet never forgets!

This is a myth. Links change, pages vanish, whole domains might evaporate or worse, change hands to owners doing the opposite of what was once there. Not all of them are archived at archive.org. sometimes nothing seems to have changed but the content of a page is changed in subtle ways. Wikipedia for example is an evolving project, pages are dynamic in their content. It is justified to call that source unstable.

Unless very basic things are referred to Wikipedia links should point to a specific version of the page.

But more importantly:

Even if a "Good Source" is not easily accessible, and you are encouraged to use alternatives when possible, then there is one way to improve on that situation that should also apply to most other citations.

Example being:

Primary literature articles behind pay walls

If you have access, then retype or copy and paste quotes from your sources. It will be a legal challenge as well as unpractical to do that with whole articles or whole books.

But the dosage makes the poison. Used sparingly this is used effectively. The core concepts or crucial statements from a primary source behind a paywall or from a printed book are even more conveniently to check then. That part quoted is more protected from link-rot and this kind of redundancy increases robustness all around.

Using short but crucial quotes improves every source.

Answer 2

What if the references aged and are obsolete. Will we require numbred references. what style one should use? If you require references, where is the style guide?