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