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CATWalk: A Guide to Critically Appraised Topics

Find the Evidence

Once you have formed a good clinical question and determined the domain in which it belongs, you are ready to begin searching the literature in order to find the evidence.  For a CAT, you will need a single study to appraise, but there are many filtered evidence-based sources that will give you an overview of the literature and their references will lead you to primary research studies.

The 6S Model of Evidence

Adapted by L. Tjosvold from: DiCenso, A,Bayley, L, Haynes, RB. Accessing pre-appraised evidence: fine-tuning the 5S model into a 6S model. Evid Based Nurs 2009;12:99-101. 

Levels of Evidence


Search filtered resources first for summaries of existing research, in order to find out what is known on your topic already.  TRIP Database is a great place to start.  TRIP is a meta-search engine of 25+ evidence-based resources. 

Clinical practice guidelines, point of care tools, and evidence-based textbooks are good summary resources (see left).  These sources typically have sections addressing each of the four domains (therapy, diagnosis, etc.).  Drug handbooks are also good for harm questions involving adverse drug reactions.



Synopses are pre-appraised descriptions of primary studies.  Good places to find synopses are DARE (also available through the Cochrane Library), ACP Journal Club, Evidence Updates, and EBM journals such as Evidence Based Medicine or Evidence Based Child Health.



Syntheses are studies that systematically appraise and synthesize evidence from primary research.  Systematic reviews, meta-analyses, and health technology assessments are examples of syntheses.  Look for these studies in the Cochrane Library (which includes the Cochrane Database of Systematic Reviews, DARE, and Health Technology Assessments).  Also try PubMed's Clinical Queries, which includes a systematic review filter.


Primary Studies

If you have not found suitable evidence using summaries, synopses, or syntheses, you will need to search the primary literature using databases like MEDLINE/PubMed, EMBASE, or Scopus.  You can use Clinical Queries in PubMed or MEDLINE to search by question domain.

EBM Resources Handout

Clinical Practice Guidelines

eBook Collections