5. Systematic Reviews and Meta Analyses

Question 1

Difference between a literature review and a systematic review?

Answer 1

Literature reviews usually do not have a section describing the methods used. They are mainly based on experience and subjectivity of the author, who is often an expert in the area. Can be methodologically flawed and biased.

A systematic review synthesises primary research with explicit methodology, and aim to appraise all relevant research on a topic.

Question 2

Why do systematic reviews provide higher quality evidence than literature reviews?

Answer 2

No evidence should be ignored, they produce an objective and balanced summary of evidence, minimises bias and reduces errors, provides a more reliable basis for decision-making.

Question 3

Why would you use PICOS?

Answer 3

To formulate systematic review research questions, define inclusion and exclusion criteria, create strategies to search in online databases of studies.

It was developed for systematic reviews of RCTs, requires adapting for different types of reviews

Question 4

What are the stages of a systematic review?

Answer 4

1. Identify issue and determine question
2. Write a protocol
3. Search for studies
4. Sift and select studies
5. Extract data from studies
6. Assess quality of studies
7. Combine the data (synthesis or meta-analysis)
8. Discuss and conclude overall findings

Question 5

What are the stages of PICOS?

Answer 5

P = Population
I = Intervention (or exposure)
C = Comparison
O = Outcome
S = Study design/setting

Question 6

What is PRISMA?

Answer 6

Preferred Reporting Items for Systematic Review and Meta Analysis. They provide reccomended reporting standards for all aspects of the systematic review process, and reccomend using a flow diagram.

Question 7

What data should be extracted from a study in a systematic review?

Answer 7

1. Details of sample size
2. The participants
3. Intervention or exposure
4. Comparison group
5. Outcome
6. Study results

Question 8

What is a meta analysis?

Answer 8

A statistical technique that combines the findings from individual studies. Allows you to produce a single pooled estimate from multiple studies.

Question 9

When should you not perform a meta analysis?

Answer 9

1. Small number of studies, needs at least 3
2. If all or most studies have high risk of bias
3. If heterogeneity is too high. Studies should be sufficiently similar in terms of effect measures and methods

Question 10

What is a funnel plot used for?

Answer 10

Measures of study presision. Studies at the top of the funnel have a larger sample size and smaller standard error. At the bottom will have smaller sample size and larger standard error.

If the greater variability in smaller studies is due to chance, they should underestimate effect as often as overestimate.

Can see if small studies that overestimate effect size will overestimate the meta analysis effect (due to publication bias not publishing negative results).

Question 11

What is a narrative synthesis?

Answer 11

An alternative to meta analysis. Summarises and synthesizes individual studies using words and tables. Allows exploration of the similarities and differences of studies, describing and understanding the literature. Many systematic reviews include a combination of meta analysis and narrative synthesis.