11 and 12 POP SCI- need to do Flashcards

1
Q

What is a systematic review? What is the purpose of a systematic review?

A

A systematic review is an overview of primary studies that used explicit and reproducible methods

Purpose: to deliver a meticulous summary of all the available primary research in response to a research question

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2
Q

Identify the four steps involved in a systematic review

A

⇒ Systematic literature search

⇒ Selection of the materials

⇒ Appraisal

⇒ Synthesis

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3
Q

What is a meta-analysis?

A

A meta-analysis is a quantitative synthesis of the results of two or more primary studies that addressed the same hypothesis in the same way

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4
Q

Illustrate the relationship between a systematic review and a meta-analysis

A

A systematic review will not necessarily include a meta-analysis if, for example, clinical heterogeneity is too great

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5
Q

State the four purposes of a meta-analysis

A
  • To facilitate the synthesis of a large number of study results
  • To systematically collate study results
  • To reduce problems of interpretation due to variations in sampling
  • To quantify effect sizes and their uncertainty as a pooled estimate
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6
Q

To ensure quality criteria, a meta-analysis should have a formal protocol.

What should be specified?

A
  • Compilation of complete set of studies
  • Identification of common variable or category definition
  • Standardised data extraction
  • Analysis allowing for sources of variation
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7
Q

How does one interpret a forest plot?

A
  • Individual odds ratios (squares) with their 95% CI (lines) are displayed for each study
  • Size of square is in proportion to the weight given to the study
  • The (diamond) is the pooled estimate with the centre indicating the pooled odds ratio (dotted line) and the width representing the pooled 95% CI
  • The (solid line) is the null hypothesis OR
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8
Q

What are the three major problems with a meta-analysis?

A
  • Heterogeneity between studies
  • Variable quality of the studies
  • Publication bias in selection of studie
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9
Q

What is the reason for publication bias?

A

Studies with statistically significant / ‘favourable’ results are more likely to be published than those studies with non-statistically significant / ‘unfavourable’ results

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10
Q

What are the consequences of publication bias?

A
  • Any systematic review / meta-analysis can be flawed by such bias
  • Publication bias leads to a biased selection of studies towards demonstration of effect
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11
Q

Identify the three steps in the method of identification of publication bias in the selection of studies

A

⇒ Check meta-analysis protocol for method of identification of studies

⇒ Plot results of identified studies against a measure of their size i.e. a funnel plot

⇒ Use a statistical test for publication bias

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12
Q

How might one interpret a funnel plot for publication bias?

A
  • If no publication bias, then the plot will be a ‘balanced’/symmetrical funnel
  • Smaller studies can be expected to vary further from the ‘central’ effect size
  • Publication bias is likely to exist if there are few small studies with results indicating small or ‘negative’ measure of effect
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