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EPI PR3144 > Systematic Review & Meta Analysis > Flashcards

Systematic Review & Meta Analysis Flashcards

1
Q

Hierarchy of Evidence (9)

- ideas, editorials, opinions

A
  1. Systematic reviews & meta analysis
  2. Randomised controlled double-blind trials
  3. Cohort studies
  4. Case-control studies
  5. Case series
  6. Case report
  7. Ideas, editorials, opinions
  8. Animal research
  9. In-vitro (test tube) research
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2
Q

Systematic review definition (4)

A
  • a clearly formulated question
  • uses systematic & explicit methods to identify, select & critically appraise relevant research
  • to collect & analyse data from the studies that are included in the review
  • may or may not use statistical methods to analyse & summarise the results (meta-analysis)
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3
Q

Meta analysis

A
  • use statistical techniques to integrate the results of several independent studies into a single quantitative estimate or summary effect size
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4
Q

Difference between Narrative Review & Systematic Review

  1. Question
  2. Sources & search
  3. Selection of independent studies
  4. Appraisal
  5. Synthesis of data
A

Narrative Review

  1. Question
    - broad in scope
  2. Sources & search
    - not specified
    - potentially bias
  3. Selection of independent studies
    - not specified
    - potentially bias
  4. Appraisal
    - variable
  5. Synthesis of data
    - often a qualitative summary

Systematic Review

  1. Question
    - focused clinical question
  2. Sources & search
    - comprehensive sources & explicit search strategy
  3. Selection
    - uniform criterion-based selection
  4. Appraisal
    - rigorous critical appraisal
  5. Synthesis of data
    - may or may not include meta-analysis
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5
Q

Purpose of Meta analysis (4)

A
  1. Increase statistical power
  2. Improve precision
    - increase sample size leads to narrower 95% CI
  3. Settle controversies arising from apparently conflicting studies or to generate new hypothesis
  4. Answer questions not posed by the individual studies
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6
Q

Relevance of systematic review to pharmacy practice (2)

A
  1. Development of evidence-based practice guidelines
  2. Economic evaluations in healthcare
    - generate clinical policies to optimise outcomes using available resources
    eg cost-effectiveness
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7
Q

**
Steps in conducting systematic review
- with or without meta analysis

(6)

A
  • *
    1. Formulate the review question & develop the systematic review protocol
    2. Search the literature
  • search strategy
  • study selection
    3. Assess quality of study
    4. Abstract data
    5. Analyse data (may include meta analysis) & interpret results
  • heterogeneity among studies (clinical, methodological & statistical)
  • publication bias
    6. Report findings
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8
Q

How to formulate the review question?

A
  • use PICO approach

Population
Intervention
Comparison
Outcome

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9
Q

Develop the systematic review protocol

- criteria to selection of studies

A
  • define the study selection criteria (inclusion & exclusion criteria)
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10
Q

Inclusion / exclusion criteria

A
  • type of study design
  • type of population
  • type of intervention
  • type of comparison
  • type of outcome
    (( PICO ))
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11
Q

Search strategy

A
  • conduct comprehensive literature search
    eg multiple electronic databases or hand searching of reference lists of publications
  • formulate search terms for electronic search
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12
Q

Examples of multiple electronic databases (3)

A
  1. PubMed
  2. Embase
  3. Cochrane Central Register of Controlled Trials
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13
Q

Study selection process (4)

A
  • based on pre-defined study selection criteria
  • record the number of studies included & excluded at each step & reason for exclusion
  • at least 2 independent reviewers to select studies
  • any discrepancies between reviewers to be resolved through discussion or third investigator
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14
Q

Assess quality of study (3)

A
  • at least 2 independent reviewers to be involved
  • any discrepancies between reviewers to be resolved through discussion or third investigator
  • 3 types
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15
Q

Types of scale to assess quality of study (2+1)

A

For RCT

  1. Jaded scale
  2. Cochrane risk-of-bias tool ver 2

For observational studies
1. Newcastle-Ottawa Scale (NOS)

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16
Q

Jaded scale (2)

A
  • RCT
  • score range from 0-5
  • low (0-2), high (3-5)
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17
Q

Disadvantage of Jaded scale

A
  • score cannot tell which part of the study is lacking unless table is reported
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18
Q

Cochrane RoB tool ver 2 (2)

A
  • RCT

- domain based (low risk of bias, some concern & high risk of bias)

19
Q

Newcastle-Ottawa Scale (NOS)

A
  • observational studies (specifically case-control & cohort studies)
20
Q

NOS for case-control studies

  • selection
  • comparability
  • ascertainment
A
  • selection of cases & controls
  • comparability of cases & control
  • ascertainment of exposure
21
Q

NOS for cohort studies

  • selection
  • comparability
  • ascertainment
A
  • selection of exposed & unexposed
  • comparability of exposed & unexposed
  • ascertainment of outcome
22
Q

Abstract data

A
  • develop a standardised data abstraction form
  • at least 2 reviewers to abstract information from studies independently
  • any discrepancies between reviewers to be resolved through discussion or third investigator
23
Q

Methods to reduce discrepancies in

  • study selection
  • assessment of study quality
  • abstract data

(2)

A
  • discussion between reviewers until consensus is reached

- invite third investigator for review & resolution

24
Q

Types of analysis of data (2)

A
  1. Qualitative data synthesis

2. Quantitative data synthesis

25
Q

Qualitative data synthesis

A
  • tabulation / graphical display of characteristics & results of individual studies
26
Q

Quantitative data synthesis
& uses
(3)

A 
- use statistical software
eg Sata, RevMan
- examine heterogeneity among studies 
eg Forest plot
- assess for publication biass 
eg Funnel plot
27
Q

Forest plot

  • square (midpoint)
  • line
  • size of square
  • diamond (midpoint)
  • width of diamond
A
  • each tree (line) represents a study
  • square is the point estimate
  • size of square is weight of the study
  • horizontal line is 95% CI
  • mid-point of diamond is summary effect measure
  • width of diamond is 95% CI of summary measure
28
Q

Weight of the study

A

= (1 / variance)

  • large sample size, smaller variance, larger weight
  • small sample size, larger variance, smaller weight
29
Q

Types of heterogeneity among studies (3)

& its stratification

A
  1. Clinical heterogeneity
    - clinical relevance
    eg doses, duration of treatment, population type, method of measuring outcome
  2. Methodological heterogeneity
    - study design & quality
    eg case-control, cohort, RCT
  3. Statistical heterogeneity
    - statistical methods
30
Q

Statistical heterogeneity among studies

A
31
Q

How to assess for statistical heterogeneity among studies (2)

A
  1. Cochran’s Q test

2. I^2 statistic

32
Q

Cochran’s Q test

A
  • chi square test

- statistically significant heterogeneity if p<0.1

33
Q

I^2 statistic

A
  • proportion of total variance due to between study variability
  • in terms of %
  • increasing value means increasing heterogeneity

= (between study variability/total variance) x 100%

34
Q

If there is statistical significant heterogeneity among studies, what model to use? (2)

A
  • use random-effects model

- to account for variability between studies

35
Q

If there is no statistical significant heterogeneity among studies, what model to use? (1)

A
  • use fixed-effects model
36
Q

Assessment for publication bias (2)

A
  • use funnel plot

- Egger’s test for funnel plot asymmetry, asymmetry if p<0.05 suggesting presence of bias

37
Q

What type of analysis is prone to publication bias?

Why? (2)

A

Meta analysis because :

  • studies with negative results are less likely to be published & mainly positive results are published & hence used in systemic review
  • hence, results from meta-analysis may overstate a treatment effect (or reduce impact of exposure)
38
Q

Funnel plot

  • x & y axis
  • description of plot (4)

(6)

A
  • y axis : size of study or precision/standard error
  • x axis : effect measure
    eg risk ratio, odds ratio
  • smaller study have wider scatter of effect estimate (bottom of pyramid)
  • larger study have narrower scatter of effect estimate
    (top of pyramid)
  • top of pyramid is the line of symmetry
  • slope of both sides of the pyramid is 95% CI of overall effect estimate
39
Q 
**
Report findings (4)
A

**
- summarise key findings
- judge validity of findings
eg poor quality studies can recommend to disregard
- judge for generalisability
- implications for further studies or clinical practice

40
Q

Reporting format for systematic reviews & meta analysis (2)

A
  1. PRISMA statement

2. MOOSE guidelines

41
Q

PRISMA statement

A

Preferred Reporting Items for Systematic reviews & Meta Analysis

42
Q

MOOSE guidelines

A

Meta analysis Of Observational Studies in Epidemiology

43
Q

Reporting guidelines

  • observational studies
  • systematic review & meta analysis
A

Observational studies
- STROBE (STrengthening the Reporting of OBservational studies & Epidemeoogy)

Systematic review & meta analysis

  • PRISMA (Preferred Reporting Items for Systematic reviews & Meta Analyses)
  • MOOSE (Meta analysis Of Observational Studies & Epidemiology)

EPI PR3144 (24 decks)

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