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EBM Resource Center: Acquire the Evidence

Acquire the Evidence

Armed with our well-built clinical questions, clinicians proceed to identify and obtain an answer from the evidence found in the health literature. There are thousands of health information resources are currently available; therefore, an understanding of the essential value of each resource type is required to determine when each one can best be applied.  Essentially, there are three general levels of literature:

Primary literature is where researchers publish their findings first. In the health field this is primarily in the form of journal articles outlining methodology, data, results, and conclusions. The evidence based approach emphasizes a hierarchy of evidence based on study types. When searching for single studies on a topic, clinicians should utilize database tools (limits and filters) to obtain the highest level of evidence to answer a clinical question. Examples:Randomized Controlled Trials, Cohort Studies, Case-Control StudiesCase ReportsQualitative Studies

Secondary literature summarizes the primary studies by appraising the relevant individual studies to answer a particular clinical question. In most cases, clinicians should initiate a search for answers to clinical questions with the secondary literature. Examples: Systematic ReviewsMeta-AnalysesEvidence-Based Guidelines, Some Clinical Database entries

There are now several online health information sources that accumulate the research (evidence) on clinical topics from the primary and secondary literature. These are often provide a very efficient way for clinicians to get up to speed on unfamiliar topics and filling holes in their knowledge base; however, clinicians should keep an eye on currency; the tertiary literature, by design, is lags behind the primary literature. Examples: Most guidelines and society statements, Most Clinical Database entries, Clinical Textbooks, Narrative Reviews


ACCESSSS from McMaster PLUS™is a service to help provide current best evidence for clinical decisions. It conducts searches simultaneously in several evidence-based information services (online evidence-based texts, evidence-based guidelines and pre-appraised journal publications). ACCESSSS also provides email alerts to newly published evidence in the user’s chosen area(s) of training/interest.

TRIP (Turning Research Into Practice)

Trip is a clinical search engine designed to allow users to quickly and easily find and use high-quality research evidence to support their practice and/or care. Trip is is a one-stop resource for filtering high-quality evidence-based research, including:

  • powerful search filtering tools (including a PICO search interface)
  • results from a variety of high quality producers of evidence based information (such as the Cochrane TRIP LogoCollaboration),
  • quick analysis of data using the Rapid Review feature,
  • rollover preview of individual results,
  • login through Facebook or Twitter,
  • tracking and favorites options for logged in users
  • sharing results through Facebook or Twitter.


PubMed is a freely available database developed and maintaned by the National Center for Biotechnology Information (NCBI) at the National Library of Medicine. It contains over 24 million citations for biomedical literature indexed in MEDLINE, life sciences journals, and electronic books. Entries from MEDLINE journals, which are chosen by a committee of experts, are abstracted and indexed with Medical Subject Headings (MeSH). 

PubMed and its search features are free for anyone to use. NYMC Health Sciences Library also provides access to MEDLINE through several of our subscription databases

NOTE: You must access PubMed via the NYMC Library homepage in order to access full text via the "NYMC Fulltext" and "NYMC Article Linker" buttons. 


DynaMed contains clinically organized summaries of nearly 1,800 topics and is updated daily from review of the research literature. Includes the Cochrane abstracts, ACP Journal Club, guidelines, USPSTF recommendations, their own reviews, as well as background materials. Available in App Store.

You must register for a DYNAMED account via the NYMC Library homepage the first time.

Cochrane Library

The Cochrane Library contains high-quality, independent evidence to inform healthcare decision-making. It includes reliable evidence from Cochrane and other systematic reviews, clinical trials, and more. Cochrane reviews bring you the combined results of the world’s best medical research studies, and are recognised as the gold standard in evidence-based health care.

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Evidence Hierarchy

Evidence Pyramid

Evidence Pyramid

Evidence Pyramid

The definition of EBM states the importance of obtaining the "best available evidence." The evidence hierarchy is an attempt to rank the health information resource/study designs with the highest quality sitting atop and the lower levels descending below. This hierarchy is helpful to guide evidence acquisition (literature searching) as well as providing clearer communication when discussing the landscape of health literature.

When it comes to prioritizing the evidence in any specific situation, clinicians will need understand the nuances of the evidence (reviews, studies) obtained. It is not uncommon for lower levels of evidence on the hierarchy to trump evidence sitting above: a hot-off the-press large RCT over an older meta analysis containing small studies.  

Levels of Evidence