Module 3 Finding the Evidence Preappraised Literature Evidence

Module 3 Finding the Evidence: Pre-appraised Literature

Evidence hierarchy Level of evidence Meta analyses Systematic reviews EBM Literature: Reviews Randomized control trials (RCTs) Controlled trials w/o randomization Individual Studies: Experimental Cohort studies Case control studies/retrospective cohort Case studies/qualitative studies Individual Studies: Observational

Review literature Systematic reviews • Address a single clinical question • Locate and validate all trials/studies relevant to the • • question (inclusion and exclusion criteria) Should include an explicit literature search Draw a conclusion, if possible, based on multiple studies Meta-analyses • Systematic reviews taken 1 step further • Look for studies where the data can be combined large • study End product is often displayed in a graphical format (forest plot)

Growth of reviews 15, 000 # published per year 12, 500 10, 000 7500 5000 2500 1990 1995 2000 2005 2010

Finding worthy reviews

DARE (CRD) commentary for: Gaster B, Holroyd J. St John's Wort for depression: a systematic review. Archives of Internal Medicine 2000; 160(2): 152 -156

Finding worthy reviews

ACP Journal Club

Finding worthy reviews

Clinical Evidence

Finding any reviews

Appraising reviews Focus Specific Questions Question Is the specific purpose of the review stated? Is the review question clearly and explicitly stated? Literature Search Were comprehensive search methods used to locate studies? Was a thorough search conducted using appropriate databases? Were other potentially important sources explored? Study Selection What types of studies are reviewed? Are they the same type? How many participants in the review? Critical Appraisal Was the validity of included studies assessed? Are the validity criteria reported? Are the inclusion criteria reported? Similarity of Groups & Treatments Are treatments similar enough to combine? Were reasons for any differences between individual studies explored? Data Synthesis Were findings from individual studies combined appropriately? Are the methods used to combine studies reported? Are the results consistent across studies?

An example Linde K, et al. 2005. St John's wort for depression: meta-analysis of randomised controlled trials. British Journal of Psychiatry 186: 99 -107

Keep in mind Still many interventions not covered by SRs • The Cochrane Database is good example of this: approximately 10 -15, 000 Cochrane reviews are needed to cover interventions that have been investigated in clinical trials. After 18 years <50% have been published (completion is est. ~30 years). Need constant upkeep • Half will need to be updated each year • Most take 6 -12 months to be developed and published

Module 3 Finding the Evidence: Pre-appraised Literature