Systematic reviews and meta analyses

Question 1

What is the importance of systematic reviews?

Answer 1

Single studies are often unable to conclusively answer a research question:

REVIEW ALL THE AVAILABLE EVIDENCE
- Efficient data searching
- Apply formal rules for critical appraisal

Question 2

Why do a systematic review?

Answer 2

1. Data quantity: increase exponentially
2. Data quality: individual studies often not conclusive
   - Poor study design or small numbers - low power - false-negative results
   - Study will often only look at one subset of the potential study population
   - multiple studies of the same research question often lead to inconsistent or even opposite results.

Question 3

What is the structure of a systematic review?

Answer 3

Structure of a Systematic Review
Stage I: Planning a Review
• Specify the question to be addressed
• Usually framed aroundPICOS:

Stage II: Conducting the Review
Identification of Research
Clearly defined search criteria (inclusion and exclusion)
Selection of Research
Study Quality Assessment to assess bias 

Stage III: Reporting and Dissemination
	• Study details tabulated in a meaningful way
	• Should include details ofPICOS
	• Often includes summary of findings 

Question 4

What is the a meta-analysis

Answer 4

• The use ofstatistical techniquesin a systematic review to integrate the results of studies matching the eligibility criteria.

combine the published estimates of effect from each study to generate a pooled risk estimate

• Calculates combined estimate of eefect from multiple studies

Question 5

What are issues in systematic reviews and meta analyses?

Answer 5

• Publication bias
○ Only subset of data available
○ Null or non-significant findings are less likely to be reported/published than statistically significant findings

• Inconsistency of results
○ Studies differ with respect to PICOS

• Low study quality
• ThisBIASmay distort meta-analyses and systematic reviews
• Inconsistency of Results

Question 6

Why would there be heterogeneity or inconsistency in the results?

Answer 6

• Studies that are trying to answer the same questions may still differ with respect to thePICOS
• Even when PICOS is the same, heterogeneity may still exist because of clinical differences, methodological differences or unknown study characteristics
• If too much heterogeneity exists it may not be appropriate to pool the studies
• Anaylse sub groups to exaine whether results differ
• Or use meta regression or sensitivtiy analysis

Question 7

What are the advantages of a meta analysis?

Answer 7

• Generate apooled overall risk estimate
• Produce a morereliable and preciseestimate of effect
• Explore differences(heterogeneity) between published studies
• Identify whetherpublication biasis occuring

Question 8

What is a systematic review?

Answer 8

answer a defined research question by collecting and summarising empirical evidence – usually published in the scientific literature – that fits prespecified eligibility criteria.

Question 9

What are the advantages of a systematic review?

Answer 9

Transparent process because of the explicit methods in identifying and rejecting studies.

A meta-analysis will increase the power of the study and enhance the precision of estimates of treatment effects, accounting for sample size, and uncertainties.

May demonstrate the lack of adequate evidence and thus identify areas where further studies are needed

Question 10

What are the limitations of a systematic review?

Answer 10

If there are too few studies matching the eligibility criteria defined,

Poor method

Publication bias

Question 11

How is publication bias analysed?

Answer 11

Funnel plots, which show whether there is a link between study size (or precision) and the effect estimate

Question 12

How is hetergeneity analysed?

Answer 12

Galbraith (radial) plots.