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BDS4 PMHP > EBD1 - Meta analysis > Flashcards

EBD1 - Meta analysis Flashcards

1
Q

What is a systematic review?

A
  • literature review that uses systematic methods to collect secondary data and critically appraise
  • provides exhaustive summary of current evidence
  • cheaper and more effective than a new study
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2
Q

How are SRs beneficial over single studies?

A
  • save readers time
  • reliable evidence
  • resolves inconsistencies
  • identify gaps in evidence
  • identify when question has been answered and no further research required (unethical to conduct further studies)
  • explores differences between studies ie dose
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3
Q

What are the key characteristics of a systematic review?

A
  • well formulated question
  • comprehensive data search
  • unbiased selection and abstraction process
  • assessment of papers
  • synthesis of data
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4
Q

What are SRs used for?

A
  • formulate policy
  • develop guidelines
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5
Q

What authors are required for a SR?

A
  • two or more
  • topic expert
  • methodological expert
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6
Q

What is the study protocol?

A

Need to set out in advance what is planned to do, so that you cannot deviate and introduce bias

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7
Q

What is the search strategy?

A
  • multiple electronic databases
  • published and unpublished data
  • no language restrictions
  • hand searching
  • grey literature (not peer reviewed)
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8
Q

What are the different types of synthesis for SRs?

A
  • qualitative (narrative)
  • quantitative (meta analysis)
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9
Q

Give examples of critical appraisal tools.

A
  • AMSTAR2
  • ROBIS
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10
Q

What makes up a well formulated question?

A

P - population
I - intervention
C - comparison
O - outcome

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11
Q

What are the different types of bias?

A
  • publication bias (positive results published more)
  • time lag bias (exciting published sooner)
  • language bias
  • citation bias
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12
Q

How do you ensure unbiased selection and abstraction process?

A
  • data extraction using predefined guidelines
  • process conducted independently by at least two reviewers
  • clear description for inclusion/exclusion
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13
Q

What are the different types of quality assessment tool?

A
  • composite scale (overall score for a paper)
  • component scale (methodological aspects are individually scored - preferred)
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14
Q

What factors are considered for risk of bias in RCTs?

A
  • sequence generation
  • allocation concealment
  • blinding
  • incomplete outcome data
  • selective outcome reporting
  • other
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15
Q

When is meta analysis inappropriate?

A
  • data is sparse
  • heterogeneity exists
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16
Q

What is meta analysis?

A
  • statistical methods to combine results of different studies
  • estimates common treatment effect across studies
  • improves precision of point estimate
17
Q

Define dichotomous data.

A
  • not a scale, binary
  • illness or not / death or not / birth or not
18
Q

Define continuous data.

A
  • scale
  • blood pressure / weight
19
Q

What summary statistic would you use for dichotomous data?

A
  • odds ratio
  • risk ratio
  • risk difference
  • NNT
20
Q

What summary statistic would you use for continuous data?

A
  • weighted mean difference
  • standardised mean difference
21
Q

How do you calculate mean difference?

A

Intervention outcome mean - control outcome mean = mean difference

22
Q

What does weighting a study mean?

A
  • more weight given to studies with more information
  • more participants, more events, lower variance
23
Q

How are results of SRs displayed graphically?

A

Forest plot

24
Q

What are the different types of heterogeneity?

A
  • clinical (variation in PICOs)
  • methodological (variation in methods)
  • statistical (variation in results)
25
Q

How do you identify statistical heterogeneity visually?

A

If you cannot draw line through all CIs

26
Q

What is chi-squared?

A

Test of heterogeneity

27
Q

What demonstrates statistically significant heterogeneity?

A

P<0.1

28
Q

What is the measure of percentage variation due to heterogeneity?

A
  • I^2
  • <50% is acceptable to pool data
29
Q

What are fixed effects?

A
  • assumes studies have same results
  • less conservative
30
Q

What are random effects?

A
  • assumes studies are slightly different
  • more conservative and have wider CI
  • preferred
31
Q

What is GRADE?

A
  • grading of recommendations assessment, development and evaluation
  • certainty of the evidence, evaluates quality
32
Q

What are the five factors of GRADE that lower quality?

A
  • high or unclear risk of bias
  • publication bias
  • inconsistency between studies
  • indirectness
  • imprecision

BDS4 PMHP (6 decks)

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