Heirarchy of evidence:
For ease of searching, sources of evidence below have been organised following the hierarchy determined by: the 5S or 5 sources model
Haynes RB. Of studies, syntheses, synopses, summaries, and systems: The "5S" evolution of information services for evidence-based healthcare decisions. Evid Based Med. 2006; 11:162-4
The most efficient sources for searching appear near the top. These sources should be consulted first as they contain pre-appraised summaries of individual studies, or syntheses of all available studies, on focused clinical topics. They may also include an assessment of the current state of the evidence in an area of clinical interest.
The lowest category in the hierarchy consists of a large number of individual primary studies. Each of these studies must be critically appraised for its applicability to a specific clinical scenario. There are not resources available for every level of this hierarchy.
- Systems (largely still hypothetical)
These are integrated computerised decision-support systems designed to improve clinician decision making. These systems, which are by no means ubiquitous, generally integrate an electronic patient health record system with some sort of evidence-based practice guidelines to generate point-of-care, patient-specific treatment recommendations.
These are online evidence summaries which are regularly updated as new evidence is generated and appraised. Conceptually similar to traditional textbooks in that they are usually arranged by clinical topic (e.g. diabetes, heart failure) for the purpose of patient management. Examples include point-of-care tools UpToDateand Best Practice, as well as evidence-based clinical practice guidelines.
Synopses are short structured abstracts of individual studies (or syntheses). They provide a brief summary and critical appraisal of a piece of research, often making recommendations for practice based on the study's quality or findings. In doing so they relieve the clinician of having to read the full article and make a judgment of its methodological quality and implications for practice.
These resources contextualise and integrate the research findings of individual studies within the larger body of knowledge of the topic. Syntheses include systematic reviews (such as those produced by the Cochrane Collaboration), the published results from consensus conferences or expert panels, meta-analyses of quantitative research, meta-syntheses of qualitative research, and critically appraised topics (CATs).
If none of the foregoing sources can provide an answer to your question, you'll need to go to the vast body of individual studies to seek evidence. This can be a time-consuming, frustrating experience if you don't know the basics of searching or the most efficient resources to use. The resources with the greatest prevalence of peer-reviewed research literature in your field should be your starting point. This should include Medline, PubMed, Embase (only available via Scopus at Flinders University) and the Cochrane Central Register of Controlled Trials (CENTRAL).
Work through the tabs above to find evidence for your topic, starting at Summaries and ending with Studies
Meta-Searches search for evidence across multiple resources. These tools return information from all levels of the pyramid.