Meta-Analysis Flashcards
How are Meta-Analysis conducted?
-Combining the results of underpowered
studies would have the effect of increasing power and reducing the risk of a type II error
-using mathematical techniques: combine the results from different trials to reach a conclusion
-Trials are brought together for a collective weighing of their results
-Individual effect sizes for each study are combined to form a common estimate
What are the advantages of Meta-Analysis?
-Increase power by increasing the sample size (combining sample size)
-Improve estimate of effect size
-Resolve uncertainty when conflicting results exist among many studies
-Improve the generalizability (external validity) of findings (f.e. one study is done in older patients, one in mid-aged, one in young -> together they cover different ages of the population or in different regions)
What are the criteria used to exclude studies from the Meta-Analysis?
-Objective of study
-Description of subjects
-Type of dependent variable
-Study design
-Method of analysis
How are the results oftentimes plotted to depict the results of all trials?
Forest Plot
-the diamond represents all data points of the trials -> significant or NOT?
What does the diamond of the Forest plot of a Meta-analysis represent?
-The top and the bottom of the diamond is directed to the value of the OR on the X-axis
-the width of the diamond represents the 95% confidence interval
What does the Cochran Q test for?
-Test for Heterogeneity
-we want to minimize the heterogeneity, we want similar studies
is the variability between the studies in the Meta-Analysis acceptable
Another test for Heterogenity
Chi^2: Chi square test
What is the purpose of Sensitivity Analysis?
determines if the final result is influenced by the inclusion of one or more studies
-one big study may cause BIAS by influencing the result of the whole meta-study -> if the meta-analysis is significant after excluding the big study the significance of the Meta-Analysis will be underlined
What is the Funnel Plot?
Checks for symmetry and balance between the distribution of the results of the studies in a “funnel” (like a normally shaped curve)
-lack of funnel shape indicates PUBLICATION BIAS -> the meta-analysis favors studies with preferable results
What is a Systematic Review?
-Highest level of evidence
-complete summary of current literature
-an author assesses the evidence for benefit or harm
-often uses meta-analysis to combine results of studies
What is a Survival Analysis
-studying patterns of change in outcome variables over time = Survival Analysis
-evaluates the ultimate outcome (endpoint: often death) and the time it takes to get there
-often in cardiovascular or cancer trials
What are the analytical models used to depict Survival curves?
-Kaplan-Meier survival curve
-Cox proportional hazard model
Kaplan Meier Survival Analysis
-everyone starts enrolled alive (at 100%) -> treatment group and control group (standard or placebo)
-stepwise design: whenever a portion of the group dies the line (step) goes down
-observe how both groups are diverse as the number of patients goes down (death) -> is there a significant difference? -> Cox proportional hazard
Cox proportional hazard
-tells if there is a statistical difference
When looking for statistical significance we assess the impact of several factors (treatment, disease severity, concomitant condition, Gender)
-uses a technique of proportional hazard regression (Cox) - to assess the effects of 2 or more variables on the time to an event
-calculates a weighting coefficient for each independent variable in a multivariable equation
Hazard Ratio
-Ratio of hazards; Hazard ratio HR
-HR = hazard in the treatment arm/hazard in the control arm
