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MED 106- RESEARCH METHODS AND ESSENTIAL MEDICAL STATISTICS > 41. LEVELS OF EVIDENCE > Flashcards

41. LEVELS OF EVIDENCE Flashcards

1
Q
  1. What are the Levels of Evidence based on?
A
  • they are based on the Oxford Center for Evidence
    based Medicine (2009)
  • there is no gold standard rule on the levels of evidence
  • they are changed and revised over time
  • other organisations have slightly different levels
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2
Q
  1. What are the Levels?
A

1a
1b
1c
2a
2b
3a
3b
4
5

NB:
- the strongest and most reliable studies are the at the
top of the list

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3
Q
  1. What is the type of study related with:
    Evidence Level 1a?
A
  • Systematic Reviews and Meta-Analysis
  • of Randomised Controlled Trials (RCT)
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4
Q
  1. What are the strengths related with:
    Evidence Level 1a?
A
  1. IT IS AN INTERVENTIONAL STUDY
    - this means that the exposure is assigned to the
    participants
    - the exposure is not assessed
  2. IT HAS HIGH INTERNAL VALIDITY
    • very low Random Error
    • very low Bias and Confounding
  3. IT HAS HIGH EXTERNAL VALIDITY
    • this is assuming that the samples are representative
    • and that there are no drop outs
  4. IT CAN PROVE TEMPORALITY IS ASSOCIATIONS
  5. IT IS THE STRONGEST EVIDENCE
    - that proves that an exposure causes an outcome
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5
Q
  1. What are the Limitations related with:
    Evidence Level 1a?
A
  1. IT DEPENDS ON THE QUALITY OF THE INCLUDED
    STUDIES
    - if the original studies are poorly conducted
    - this cannot be fixed
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6
Q
  1. What is the type of study related with:
    Evidence Level 1b?
A
  • High Quality Randomised Controlled Trials
  • that are individual studies

THESE STUDIES:
- have narrow confidence intervals
- they have a low drop out rate
- random allocation takes place

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7
Q
  1. What are the strengths related with:
    Evidence Level 1b?
A
  1. IT IS AN INTERVENTIONAL STUDY
    - this means that the exposure is assigned to the
    participants
    - the exposure is not assessed
  2. IT HAS HIGH INTERNAL VALIDITY
    • very low Random Error
    • very low Bias and Confounding
  3. IT CAN PROVE TEMPORALITY IS ASSOCIATIONS
  4. IT IS A STUDY THAT CAN INFER CAUSALITY
    - this proves that an exposure causes an outcome
    - but this has to be assumed with caution
    - since we are only looking at a single study
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8
Q
  1. What are the Limitations related with:
    Evidence Level 1b?
A
  • this is only a single study
  • the External Validity could be low
  • this is definitely the case if the study sample is too
    specific
  • this means that it will not be representative
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9
Q
  1. What type of study is related with:
    Evidence Level 1c?
A
  • high quality studies
  • they are not randomised
  • they are not controlled
  • they are individual studies

THESE STUDIES HAVE:
- a low drop out rate
- a narrow confidence interval

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10
Q
  1. What are the strengths related with:
    Evidence Level 1c?
A
  1. IT IS AN INTERVENTIONAL STUDY
    - this means that the exposure is assigned to the
    participants
    - the exposure is not assessed
  2. IT HAS MODERATE INTERNAL VALIDITY
    • it has a lower bias than in Observational Studies
  3. IT CAN PROVE TEMPORALITY IS ASSOCIATIONS
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11
Q
  1. What are the limitations related with:
    Evidence Level 1c?
A
  1. IT IS PRONE TO CONFOUNDING
    - this is because of the lack of Randomisation
  2. THE EXTERNAL VALIDITY IS LOW
    • since we are dealing with a single study
    • the study can be too specific
    • this means that it is not representative
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12
Q
  1. What is the type of study related with:
    Evidence Level 2a?
A
  • Systematic reviews and Meta-Analysis
  • of Cohort Studies
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13
Q
  1. What are the strengths related with:
    Evidence Level 2a?
A
  1. IT HAS AN ACCEPTABLE INTERNAL VALIDITY
    • very large sample
    • low Random error
  2. IT CAN PROVE TEMPORALITY IS ASSOCIATIONS
  3. HIGH EXTERNAL VALIDITY
    - only if we assume that the samples are representative
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14
Q
  1. What are the limitations related with:
    Evidence Level 2a?
A
  1. PRONE TO BIAS AND CONFOUNDING
    • this is because of the Methodological limitations
    • the study is observational
  2. CAUSALITY CAN NOT BE INFERRED
    - we can not state that the outcome is caused by the
    Exposure
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15
Q
  1. What is the type of study related with:
    Evidence Level 2b?
A
  1. These studies can be high quality Cohort studies
    • these studies are individual

THESE STUDIES:
- have narrow confidence intervals
- they have low drop out rates
- they have accurate assessments
- they are adjusted for confounding

  1. These studies can be low Quality Randomised Control
    Trials (RCTs)
    • they are individual studies

THESE STUDIES HAVE:
- wide confidence intervals
- they have a high drop out rate
- random allocation is not maintained

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16
Q
  1. What are the strengths related with:
    Evidence Level 2b?
A
  1. IT HAS AN ACCEPTABLE INTERNAL VALIDITY
    • the sample is large
    • random error is low
    • this applies only for the Cohort Studies
  2. IT CAN PROVE TEMPORALITY IS ASSOCIATIONS
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17
Q
  1. What are the limitations related with:
    Evidence Level 2b?
A
  1. IT IS PRONE TO BIAS AND CONFOUNDING
    • this is due to the methodological limitations
      of the included studies
  2. CAUSALITY CAN NOT BE INFERRED
    - we can not state that the outcome is caused by the
    exposure
18
Q
  1. What type of study is related with:
    Evidence Level 3a?
A
  • Systematic Reviews and Meta-Analysis
  • of Case-Control studies
19
Q
  1. What are the strengths related with:
    Evidence Level 3a?
A
  1. A VERY LARGE SAMPLE IS USED
    - the Random Error is low
  2. IT HAS HIGH EXTERNAL VALIDITY
    • assuming that the sample is representative
20
Q
  1. What are the limitations related with:
    Evidence Level 3a?
A
  1. LOW INTERNAL VALIDITY
    - there is Bias present
    - there is Confounding
  2. CANNOT PROVE TEMPORALITY IN ASSOCIATIONS
  3. CAUSALITY CANNOT BE INFERRED
    - we cannot state that the outcome is caused by the
    exposure
21
Q
  1. What type of study is related with:
    Evidence Level 3b?
A
  • high quality Case Control studies
  • they are individual cases

THESE STUDIES HAVE:
- narrow confidence intervals
- accurate assessments
- no serious recall bias
- adjustments for Confounding

22
Q
  1. What are the strengths related with:
    Evidence Level 3b?
A
  1. THE SAMPLE IS LARGE
    - random error is low
23
Q
  1. What are the limitations related with:
    Evidence Level 3b?
A
  1. LOW INTERNAL VALIDITY
    - there is bias present
    - there is Confounding
  2. CANNOT PROVE TEMPORALITY IN ASSOCIATIONS
  3. CAUSALITY CANNOT BE INFERRED
    - cannot state that the outcome is caused by the
    exposure
24
Q
  1. What type of study is related with:
    Evidence Level 4?
A
  1. CASE-SERIES
    - this is the follow-up of patients that receive specific
    treatments
    - we look at their prognosis
  2. CROSS-SECTIONAL STUDIES
  3. LOW QUALITY COHORT AND CASE-CONTROL STUDIES
    - they have a wide confidence interval
    - they have a high bias
    - they are affected by Confounding
25
Q
  1. What are the strengths related with:
    Evidence Level 4?
A
  1. IT IS EASY TO CONDUCT
  2. IT IS CHEAP
  3. IT CAN GENERATE A HYPOTHESES
    - this can be used for further and higher quality
    research
26
Q
  1. What are the limitations related with:
    Evidence Level 4?
A
  1. IT HAS A VERY LOW INTERNAL VALIDITY
    - random error
    - bias
    - confounding
  2. IT CANNOT PROVE TEMPORALITY IN ASSOCIATIONS
    - except for Cohort studies
  3. CAUSALITY CANNOT BE INFERRED
    - we cannot state that the outcome is caused by the
    exposure
  4. THE EXTERNAL VALIDITY IS LOW
27
Q
  1. What types of studies are related with:
    Evidence Level 5?
A
  1. INDIVIDUAL EXPERT OPINIONS AND REPORTS
  2. EXPERT COMMITTEE OPINIONS AND REPORTS
  3. CLINICAL EXPERIENCES OF RESPECTED AUTHORITIES
28
Q
  1. What are the strengths related with:
    Evidence Level 5?
A
  1. VERY EAST TO CONDUCT
  2. CHEAP TO CONDUCT
  3. CAN GENERATE A HYPOTHESIS
    - that can be used for higher quality research
29
Q
  1. What are the limitations related with:
    Evidence Level 5?
A
  1. DO NOT QUALIFY AS SCIENTIFIC RESEARCH
  2. NOT BASED ON EMPIRICAL RESEARCH FINDINGS
    - it is just based on clinical observations
  3. THE INTERNAL VALIDITY IS EXTREMELY LOW
  4. THE EXTERNAL VALIDITY IS EXTREMELY LOW
  5. CANNOT INFER CAUSALITY AT ALL
    - we cannot state that the outcome is a result of the
    exposure
30
Q
  1. What are the four factors that determine the Strength of Recommendation?
A
  1. The Quality of Evidence
  2. The balance between the desirable and undesirable
    effects
  3. Values and preferences
    - such as the patients, the professionals, the
    paymasters and the public
  4. Cost
    - how the available resources are utilised
31
Q
  1. Does strong level evidence always mean strong recommendations?
32
Q
  1. What can be said about RCT results and Observational Study results?
A
  • always believe the RCT results
33
Q
  1. What do we use the “GRADE” guidelines to establish?
A
  • we use them to establish the Quality of Evidence
  • it grades the strength of recoomendations
34
Q
  1. What do the “GRADE” guidelines analyse?
A
  1. IMPRECISION
    - this is done by using the 95% Confidence Interval
  2. LIMITATIONS IN THE STUDY DESIGN (BIAS):
    - this looks at the quality
  3. INCONSISTENCY OF RESULTS
    - this looks at the Heterogeneity
  4. PUBLICATION BIAS
    - this looks at the Publication Bias
  5. INDIRECTNESS OF EVIDENCE
    - this looks at the generalisability of the data
35
Q
  1. Why do we rate the Certainty in the Evidence and the Strength of the Recommendations?
A
  1. IT HELPS US TO JUDGE THE EVIDENCE
    - and the recommendations in Healthcare
  2. CLINICAL ACTIONS
    - are likely to differ
    - this depends on whether one concludes that the
    evidence is high or low
  3. TO DECIDE WHETHER THE HEALTH BENEFITS
    - are worth the additional costs
  4. HELPS TO IMPROVE COMMUNICATION
    - of the practice guidelines
36
Q
  1. What kind of studies are given a High Quality Rating based on the GRADE System?
A
  • Randomised Trials (RCT)
  • Double Upgraded Observational Studies
37
Q
  1. What kind of studies are given a Moderate Quality Rating based on the GRADE System?
A
  • Downgraded Randomised Trials (RCT)
  • Upgraded Observational Studies
38
Q
  1. What kind of studies are given a Low Quality Rating based on the GRADE System?
A
  • Double Downgraded Randomised Trials (RCT)
  • Observational Studies
39
Q
  1. What kind of studies are given a Very Low Quality Rating based on the GRADE System?
A
  • Triple Downgraded Randomised Trials (RCT)
  • Downgraded Observational Studies
  • Case Series
  • Case Reports
40
Q
  1. What are factors that can decrease the Quality level of data evidence?
A
  1. Limitations in the design
  2. Limitations in the implementation of the studies
  3. Bias
  4. Indirect Population
  5. Indirect Intervention
  6. Indirect Control
  7. Indirect Outcomes
  8. Unexplained Heterogeneity
  9. Inconsistency of Results
  10. Problems with subgroup analyses
  11. Imprecision of Results
  12. Wide Confidence Intervals
  13. High probability of Publication Results
41
Q
  1. What are factors that can increase the Quality Level of data evidence?
A
  1. Large Magnitude of Effect
  2. All possible confounding is adjusted for
  3. There is a dose-response gradient

MED 106- RESEARCH METHODS AND ESSENTIAL MEDICAL STATISTICS (43 decks)

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