Systematic Reviews

Question 1

What are systematic reviews?

Answer 1

• Review of all literature
• On one particular topic/question
• Using scientific methods

Question 2

Reasons for differences between RCTs

Answer 2

• Chance
• Differences in people
• Differences in intervention/comparator
• Differences in care other than that being investigated
• Differences in the way treatment effects are assessed
• Differences in follow-up
• Reporting of the available evidence
• Selection from the available evidence

Question 3

What is publication bias?

Answer 3

When publication of research results depends on their nature and direction

Question 4

Types of publication bias

Answer 4

• Positive result bias
• Outcome reporting bias

Question 5

What is positive result bias?

Answer 5

When authors are more likely to submit, or editors accept, positive than negative or inconclusive results

Question 6

What is outcome reporting bias?

Answer 6

When several outcomes within a trial are measure but are reported selectively depending on the strength and direction of those results

Question 7

Issues systematic reviews attend to

Answer 7

• Large volume of information
• Low-quality information drowns out high-quality?
• Cannot find/read the right evidence for the specific needs
• Must critically evaluate the methodological rigor and statistically analyse each study

Question 8

Review definition

Answer 8

Any attempt to summarise information

Question 9

Benefits of reviews

Answer 9

• Volume of literature condensed
• New information made accessible
• Some have taken considerable time to find all info + review topic well

Question 10

Hierarchy of evidence for effectiveness (top to bottom)

Answer 10

• Systematic reviews
• RCTs
• Cohort studies
• Case control studies
• Case series’ + reports
• Expert opinion, “anecdotal” evidence

Question 11

Stages in a systematic review

Answer 11

• Define question
• Write protocol
• Search for evidence/studies
• Select relevant evidence
• Appraise studies
• Extract, analyse + summarise data
• Interpret review results
• Discussion + conclusion

Question 12

What criteria are used to define the question for a systematic review?

Answer 12

PICO:
- Population
- Intervention
- Comparison
- Outcome

Question 13

What is a meta-analysis?

Answer 13

Statistical technique used to combine the quantitative results from a number of studies

Question 14

Advantages of a systematic review

Answer 14

• Can be best source of evidence
• Assimilation of large amounts of research
• Provide reliable, unbiased estimates of effect
• Increase precision of estimates of effect
• Provide info about generisability + consistency of effect
• Identify what info is missing
• Useful for making decisions

Question 15

What is internal validity?

Answer 15

Degree to which the effect of the observed is attributable to the evidence, rather than any other cause

Question 16

What is external validity?

Answer 16

Degree to which the review’s conclusions apply to other person in other places/times

Question 17

3 parts of the critical appraisal process

Answer 17

• Is the review trustworthy/valid? (internal validity)
• What were the results?
• How will the results help? (external validity)

Question 18

10 critical appraisal questions for a systematic review

Answer 18

• Did the review ask a clearly focused question
• Did the review include the right type of study
• Did the reviewers try to identify all relevant studies
• How did the reviewers decide which studies to include + did they assess the quality of the included
• If the results of the studies have been combined, was it reasonable to do so
• How are the results presented and what is the main result
• How precise are these results
• Can the results be applied to the local population
• Were all important outcomes considered
• Should policy or practice change as a result of the evidence contained in the review