module 3 finding the evidence: pre-appraised literature
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Module 3Module 3Finding the Evidence:Finding the Evidence:Pre-appraised LiteraturePre-appraised Literature
EBM Literature: Reviews
Individual Studies:Experimental
Lev
el o
f ev
iden
ce
Individual Studies:Observational
Evidence hierarchy
Randomized control trials (RCTs)Controlled trials w/o
randomization
Cohort studiesCase control studies/retrospective
cohortCase studies/qualitative studies
Meta analysesSystematic reviews
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)
Review literature
1990 1995 2000 2005
2500
12,500
5000
10,000
7500
# pu
blis
hed
per
year
15,000
2010
Growth of reviews
Finding worthy reviews
DARE
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
Focus Specific Questions
QuestionIs the specific purpose of the review stated?Is the review question clearly and explicitly stated?
Literature SearchWere comprehensive search methods used to locate studies?Was a thorough search conducted using appropriate databases?Were other potentially important sources explored?
Study SelectionWhat types of studies are reviewed? Are they the same type? How many participants in the review?
Critical AppraisalWas 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 SynthesisWere findings from individual studies combined appropriately?Are the methods used to combine studies reported?Are the results consistent across studies?
Appraising reviews
Linde K, et al. 2005. St John's wort for depression: meta-analysis of randomised controlled trials. British Journal of Psychiatry 186:99-107
An example
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
Keep in mind
Module 3Module 3Finding the Evidence:Finding the Evidence:Pre-appraised LiteraturePre-appraised Literature
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