Systematic reviews and meta analysis

Question 1

What is a systematic review?

Answer 1

A review of a clearly formulated question that uses systematic and explicit methods to identify, select, and critically appraise relevant research, and to collect and analyse data from the studies that are included in the review.

Question 2

What is a meta analysis?

Answer 2

The statistical techniques used in a systematic review

Question 3

Why do we need systematic reviews?

Answer 3

Because data quantity has increased over time. We also need SRs to assess the quality of evidence

Question 4

What are the main advantages of a systematic approach?

Answer 4

It is transparent process due to explicit methods in identifying and rejecting studies

Meta analysis increases power of study and enhance precision of estimates of treatment effects, accounts for sample size and uncertainties

They show which areas need further studies

Question 5

What are steps involved in systematic review?

Answer 5

Stage 1: planning review
Stage 2: identification of research, selection of studies, study quality assessment
Stage 3: reporting dissemination

Question 6

What are advantages of a meta analysis?

Answer 6

More subjects can be included- more precise estimate of effect and differences between published studies can be explored. You can also identify whether publication bias is occurring.

Question 7

What are the limitations of meta analysis?

Answer 7

Publication bias, labour intensive, inconsistency of results, low study quality

Question 8

How do you visually summarise results of meta analysis?

Answer 8

Forest plot

Question 9

What is publication bias?

Answer 9

The greater likelihood of research with statistically significant results to be published in the peer-reviewed literature

Question 10

How can you explore publication bias?

Answer 10

Funnel plots

Question 11

Why might heterogeneity occur?

Answer 11

Due to differences in interventions, outcomes, study designs

Question 12

How can heterogeneity be explored?

Answer 12

Galbraith (radial) plots

Question 13

What are the limitations of systematic reviews?

Answer 13

If there are too few studies matching eligibility criteria, SR is not v. beneficial. If quality of studies is inadequate, findings of SR are compromised. Publication bias can distort findings.

Question 14

What does the size of a box in a forest plot indicate?

Answer 14

Weight given to the overall study

Question 15

What do the horizontal lines in a forest plot indicate?

Answer 15

95% confidence interval

Question 16

What does the the diamond in a forest plot show?

Answer 16

The overall estimate. the centre of the diamond and dashed line shows the summary effect estimate and the width of the diamond refers to the confidence interval.

Question 17

What does a symmetrical funnel plot indicate?

Answer 17

No publication bias

Question 18

What should reporting a systematic review involve?

Answer 18

PICOS: populations, interventions, control, outcomes and study design

Question 19

When is Tau squared test used?

Answer 19

In the estimate of between-study variance based on random effect model

Question 20

When is the Chi squared test used?

Answer 20

Test of statistical significance for heterogeneity (lower power)

Question 21

When is the I squared test used?

Answer 21

Measure or index of heterogeneity

Question 22

What is the difference between a fixed effects and random effects model in a meta analysis?

Answer 22

A fixed effect meta-analysis assumes all studies are estimating the same (fixed) treatment effect, whereas a random effects meta-analysis allows for differences in the treatment effect from study to study.