Searching for Evidence
Searching for Evidence
There are many point-of-care tools that present some evidence from the literature, e.g. DynaMed, FirstConsult, Up-to-Date, but none of these resources cover every condition, not every entry has evidence, and not every entry is current, so it is important to know how to find evidence in the biomedical literature.
Evidence Based Medicine Resources from the National Library of Medicine.
PubMed [ searches the biomedical literature indexed by the National Library of Medicine. There is a huge range of literature, from editorials and case studies, to randomized control trials and systematic reviews. PubMed has recently started including chapters from some online books available through the National Center for Biotechnology Information (NCBI).
There are several strategies to help with finding evidence-based resources using PubMed.
One strategy is to limit your search to the relevant article types. Just do a search with the usual keywords and/or MeSH headings that you would normally use, and then use the Limits to narrow your search to the ‘Type of Article’ that you would like to find; Meta-Analysis, Practice Guideline, Randomized Control Trial, and Clinical Trial are all good sources for evidence.
PubMed’s Clinical Queries  are a good way to go directly to the evidence. As with the Limits search mentioned above, just enter your search using keywords or MeSH headings and then you will have a choice of looking at articles based on Clinical Study Categories, Systematic Reviews (especially helpful for EBM), or Medical Genetics. The filters that have been programmed to help refine your search have been extensively tested and proven to provide excellent information. There are five study Clinical Study Categories:
- Etiology - causation/harm in disease and diagnostics
- Diagnosis - disease diagnosis
- Prognosis - disease prognosis
- Clinical prediction guidelines - data addressing the likelihood of disease presence or absence
- Therapy - treatment of disease
And these can all have a different emphasis:
- Narrow - a specific search that will retrieve fewer more precise, relevant citations
- Broad – a sensitive search that includes more citations but some will be peripheral to the subject
If you regularly search topics with one of the Clinical Queries, you might want to use MyNCBI to set up some filters that will allow you to see how many articles are in each category. Just go to 'MyNCBI Site Preferences' - on the upper left of the screen when you sign into MyNCBI - and under PubMed Preferences, go to 'PubMed Filters & Icons'. Choose the Properties category where you will see Clinical Queries. Use the + to view all the options and choose the combinations that are most useful for you. When you search PubMed, be sure to sign into MyNCBI first, and then you will see all the categories and the number of articles in each along the right side of the screen as Filters.
Images for the above search strategies can be found by going to the Searching PubMed for Evidence tab (far right)of the Evidence-Based Medicine Research Guide created by this page's author for Virginia Commonwealth University Libraries 
PubMed Health  is a new resource from the National Library of Medicine, specializing in reviews of clinical effectiveness research, with easy-to-read summaries for consumers as well as full technical reports. PubMed Health pulls together information from many agencies: summaries from The Cochrane Collaboration and the National Health Service (NHS) National Institute for Health Research (NIHR) Health Technology Assessment Programme, and full text reviews from the U.S. Agency for Healthcare Research and Quality (AHRQ), the Drug Effectiveness Review Project (DERP) at Oregon Health & Science University (OHSU), England's National Institute for Health and Clinical Excellence (NICE) guidelines program, and the Department of Veterans Affairs' Evidence-based Synthesis Program.
PubMed Health includes consumer, executive/policymaker, and clinical summaries of systematic reviews as well as the full-text of systematic reviews. There is also a medical encyclopedia that presents medical and drug information for consumers. The results page allows you to choose the type of summary you want, view your topic in the Medical Encyclopedia, or find other systematic reviews with a PubMed Clinical Queries search.
Other Places to Search for Evidence
EvidenceUpdates ( ) is a free service that offers synopses of articles from 120 clinical journals, rated for clinical relevance using the McMaster Online Rating of Evidence (MORE). These services can help a physician decide which studies are worth reading.
The Cochrane Library
The Cochrane Library () includes Cochrane Database of Systematic Reviews (produced by the Cochrane Collaboration), Database of Reviews of Evidence (DARE), Cochrane Central Register of Controlled Trials, and other method, technology and economic assessments.
National Guidelines Clearinghouse (NGC)
National Guidelines Clearinghouse (NGC) () is a public resource for evidence-based clinical practice guidelines collected by the Agency for Healthcare Research and Quality (AHRQ). The collection is not large but there are Guideline Syntheses for some topics and Expert Commentaries for others that are quite helpful.
AHRQ also has separate pages on Evidence-based Practice, Outcomes & Effectiveness, Technology Assessment, and more as part of their Clinical Information service ().
TRIP (Turning Research into Practice) () searches many of the resources listed here, and many more. Some of the specialty guideline databases covered by TRIP have a limited number of reviews, so by combining them all together with one search, it makes combing the evidence-based Syntheses sites much easier to access.
Submitted by Margaret Henderson