Levels of evidence and Interpretation of a systematic

Levels of evidence and Interpretation of a systematic review

THE HIERARCHY OF EVIDENCE 1 a. Systematic review with homogeneity of RCTs 1 b. RCT with narrow confidence interval 2. Cohort studies with > 80% follow up 3. Case control study 4. Case series and poor quality cohort/ case control 5. Expert opinion Evidence based Medicine: Sharon Strauss 4 th edition

SYTEMATIC REVIEW AND META ANALYSIS • Meta analysis- A statistical technique used to combine the results of several studies addressing the same question into a single summary measure • Systematic reviews do not have to have a meta- analysis

THE COCHRANE COLLABORATION International non-profit organisation that prepares, maintains, and disseminates systematic up -to-date reviews of health care interventions

FOREST PLOT �Graphical representation of a meta analysis �“Forest of lines” �Originated in 80’s �Modern forest plot - 1998

HOW TO READ A FOREST PLOT Individual studies

HOW TO READ A FOREST PLOT Effect estimate for each study Pooled estimate

HOW TO READ A FOREST PLOT Confidence intervals of individual studies’ effect estimate CI of pooled estimate

HOW TO READ A FOREST PLOT Favours intervention Line of no effect Favours control

WHAT ELSE DOES THE FOREST PLOT SHOW? Method/ Model used Weight Heterogeneity Effect estimate for each study

FOREST PLOT FOR CONTINUOUS VARIABLES �Mean difference instead of relative risk

LEARNING POINTS IN THIS PODCAST Ø Levels of evidence Ø Systematic review and meta analysis Ø Forest plot – Components Interpretation