There is a range in quality of evidence available in the literature, with meta-analysis and systematic reviews being the very highest quality. As you move up the pyramid, the amount of literature decreases but its clinical relevance increases.
Sources of research may be either pre-appraised (summaries), primary literature or more anecdotal.
|Meta-analysis or Systematic Reviews||PubMed, CINAHL, Cochrane Library, PEDro|
|Critically-Appraised Topics||Clinical Key, UpToDate|
|Critically-Appraised Articles||ACP Journal Club|
|Randomized Controlled Trials||Original articles (search CINAHL, PubMed, PEDro)|
|Cohort Studies||Original articles (search PubMed)|
|Case-Controlled Studies etc.||Original articles (search CINAHL, PubMed)|
|Background Info/Expert Opinion||Books, editorials (search print & e-books, CINAHL, PubMed)|