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Foundations 3 > EBM revision > Flashcards

EBM revision Flashcards

1
Q

What do you need to consider when you want to treat a patient with a drug?

A
  • benefits vs harms
  • costs
  • patient preference
  • ethics
  • can you use the drug in your patient population?
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2
Q

What is the need for randomisation?

A

Both the known and unknown characteristics of the study population that might affect the outcome of trial are distributed by chance. This reduces allocation bias as well.

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3
Q

What do these levels of measurement mean?

  • Nominal
  • Ordinal
  • Interval
A

Nominal- categorical
Ordinal- rank-ordered
Interval- presented as ranges

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4
Q

What are the main biases associated with RCT?

A
  1. Allocation bias
  2. Performance bias
  3. Detection bias
  4. Performance bias
  5. Reporting
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5
Q

What is allocation bias?

A

Systematic difference that exists in the baseline characteristics between the groups in the trial.

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6
Q

How to reduce allocation bias?

A

Randomisation using a random sequence generator, allocator concealment

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7
Q

What is performance bias?

A

Systematic difference in the care given and external factors that may affect outcome that are not the intervention of interest.

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8
Q

How to reduce performance bias?

A

Blinding the participants and personnel

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9
Q

What is detection bias?

A

Systematic difference in how outcomes are measured/

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10
Q

How to reduce detection bias?

A

Blind the outcome assessor

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11
Q

What is attrition bias?

A

Systematic differences in the groups that have withdrew from the study compared to those who stayed on

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12
Q

What should you be looking for in terms of attrition bias?

A

incomplete outcome data

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13
Q

What is reporting bias?

A

Systematic differences between reported and unreported findings

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14
Q

What should you be looking for in terms of reporting bias?

A

Proof of something that was measured but not reported

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15
Q

What factors may lead to allocation bias if not blinded?

A

Not wanting to disadvantage patients who are old/young, poor health, vulnerable patients

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16
Q

What are the ethical issues that could be raised from an RCT?

A

Could we possibly giving patients a drug that could cause a lot of s/e compared to standard treatment and one that may not be as effective?
Are we disadvantaging the control group if this drug is actually more effective

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17
Q

How do we reduce cross-over?

A

Cluster randomisation

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18
Q

2 Methods of analysis of outcome:

A
  1. intention to treat: based on the initial allocation of treatment.
  2. according to treatment received: treatment received coherent with the protocol of the trial which they were originally allocated to.
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19
Q

Where can you look for study population?

A

List/register- GP lists, cancer and professional registers, hospital and clinic registers

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20
Q

What are the 3 modes of randomisation?

A
  • Simple
  • Cluster
  • Stratification
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21
Q

How is simple randomisation conducted?

A

using random number generator

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22
Q

How is cluster randomisation conducted?

A

perform in schools, hospitals, gp practices

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23
Q

What is the downside of cluster randomisation?

A

Special analytical tests need to be conducted to account for the similarities within the groups.

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24
Q

How is stratification randomisation conducted?

A

Greater proportion of minority groups are recruited to increase power and sample size

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25
Q

What are the non-random methods?

A
  • Systematic
  • Convenience
  • Snowball
  • Street survey
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26
Q

What is the systematic method?

A

every nth selected

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27
Q

What is the convenience method? and the problem with this?

A

volunteers recruited –>volunteer bias

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28
Q

What is snowball?

A

recommendation of a friend from a pre-set requisite

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29
Q

What is street survey?

A

Open polls and market research

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30
Q

What is bias?

A

Systematic error in the study design, conduct or analysis that results in deviation from the truth

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31
Q

What is a random error?

A

All measurements deviate from the centre of target in different directions due to unknown and unpredictable changes in the experiment

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32
Q

What is sampling bias?

A

Systematic difference in the characteristics of those selected into the study compared to those who weren’t.

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33
Q

What is spectrum bias? Which study is it seen in?

A

Specific groups inappropriately excluded. DTA

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34
Q

What is interviewer bias?

A

Error due to interviewer’s subconscious/conscious gathering of data that differs systematically between cases and controls

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35
Q

What is recall bias? When can it be avoided?

A

incompleteness/inaccuracy recall of prior exposure of interest between cases and controls. Avoided in cohort study

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36
Q

What is recording bias?

A

Cases have a more detailed recording of data compared to controls.

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37
Q

What is verification bias? what study is it seen in?

A

Systematic error in DTA where not all participants received both the index and reference standard.

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38
Q

What is the main thing to note in qualitative research?

A

Reflexive stance of the researcher, their background, beliefs, personality influences their relationship and interaction with participants and may influence the outcome of the study.

39
Q

What is a confounding factor?

A

An additional factor that can independently have an effect on the exposure of interest and with the outcome of the study.

40
Q

Which study design theoretically does the confounding factor not influence very much?

A

RCT because known and unknown confounders are evenly distributed through randomisation.

41
Q

How can confounders be adjusted in studies other than RCT?

A

Matching studies in case control and cohort trial.

42
Q

What are the 9 criteria for causality?

A
  • Temporality: time sequence exposure before effect
  • Strength: stronger the association, more you believe it
  • Biological gradient: dose-response relationship
  • Consistency: many different studies coming to similar conclusions
  • Plausibility: biological mechanism either known/postulated that may support association
    (TCBPS)
  • Coherence: Should not contradict current knowledge
  • Experiment/Reversibility: when cause removed, disease does not occur
  • Specificity: cause associated with one disease only (rare)
  • Analogy: clear cut analogy present
43
Q

What is incidence?

A

Total number of new cases during a specified period in a specified population.

44
Q

What is prevalence?

A

Total number of individuals with the disease at a particular time

45
Q

How to measure incidence rate?

A

New cases/person-time accumulated

46
Q

Measure incidence risk:

A

new cases/number at risk

47
Q

Measure prevalence:

A

Incidence x duration of disease

48
Q

Measure point prevalence:

A

number at some time point/total population at risk at that point

49
Q

Measure period prevalence:

A

number over a period/total population seen over that period

50
Q

What are the 2 ways effect can be expressed?

A

Risk ratio or risk difference

51
Q

What are case reports/series?

A

Detailed report of either individual or series of patients

52
Q

What are the advantages of it?

A
  • Good for unusual disease

- Forming hypothesis

53
Q

What are cross-sectional studies?

A

Used to determine point prevalence of a particular study.

Find sample population from target pop–> collect data

54
Q

What are the advantages of cross-sectional studies?

A

Cheap, quick

55
Q

What are the disadvantages of cross-sectional studies?

A
  • Cannot determine causality ( time-sequence, biological gradient, coherence, strength, plausibility)
  • Unable to interpret survival because they are most likely to be less aggressive diseases
56
Q

What is an ecological study?

A

Measure of rate of death/disease in populations at risk.

57
Q

What are the advantages of an ecological study?

A
  • Quick
  • Cheap
  • Good to generate hypothesis
58
Q

What are the disadvantages of an ecological study?

A
  • Confounding factors
  • Sampling bias
  • Information bias
  • Unclear causality relationship
  • Not on individual level
59
Q

How do you analyse ecological studies?

A

Scatter plot, Pearson’s correlation

60
Q 
What do the following r values for Pearson's correlation mean? 
r=1
r=0.8
r=0.5
r=-1
A

correlation present
strong correlation
moderate correlation
negative correlation

61
Q

What is a cohort study?

A

Groups of individual defined on the basis of their exposure to risk factor then followed over time to observe if they develop the disease

62
Q

Cohort studies can be conducted in 2 methods. What are they?

A
  • Prospective: exposure measured at baseline and followed up

- Retrospective: trace back for exposure info

63
Q

What are the advantages of prospective to retrospective studies?

A

exposure accurately measured, confounders can be assessed

64
Q

What are the disadvantages of prospective to retrospective studies?

A

it is expensive, time consuming

65
Q

What are the main advantages of cohort studies?

A
  • Minimise recall bias
  • Good causal effect
  • Can monitor many diseases
  • Can be used for rare exposures
66
Q

What are the main disadvantages of cohort studies?

A
  • Not useful for rare diseases
  • Expensive and time consuming
  • Attrition bias
67
Q

What is a case control study design?

A

Aetiological factors (the cause of disease), incidence and prevalence cases

68
Q

What are the advantages of case control?

A
  • Study rare disease
  • Explore multiple risk factors
  • Good for diseases with long latency periods
69
Q

What are the disadvantages of case control studies?

A
  • Selection bias
  • Causality cannot be formed
  • Single disease
  • Cannot estimate absolute risks
70
Q

What types of analysis conducted in case control studies?

A
  • matched: conditional logistic regression

- unmatched: logistic regression

71
Q

What methods are used to adjust for confounders?

A

Cox regression, randomisation, stratified analysis, matching

72
Q

What are the strengths of qualitative evidence?

A
  • real world patient
  • high level of detail and content
  • capture experience and understanding
73
Q

What are the weaknesses of qualitative evidence?

A
  • generalisable with caution
  • need to trust researcher
  • cannot predict causation
74
Q

What method of data collection used in qualitative research?

A

Iterative method where collection and analysation of data occurs over and over again until saturation is reached and emerging themes are identified

75
Q

What tool do we use to appraise qualitative research?

A

CASP tool

76
Q

What are the 2 types of errors that may occur in qualitative research?

A

I- stating something that is not there–> little evidence can be found on how that conclusion was achieved
II- Ignoring something that is there

77
Q

What does the Diagnostic Test Accuracy study encompass?

A

Comparison of disease state estimated by the index test (new test of interest) compared to reference standard

78
Q

What are the 2 important information one needs to know about a patient before recruiting them?

A
  • Presentation of disease

- Prior tests

79
Q

What are the 3 main types of bias present in DTA?

A
  • Spectrum bias: inappropriately excluding patients that are difficult to diagnose
  • Verification bias: patients who received the index test may not always get the reference standard test
  • Review bias: Interpretation of index test results not independent of standard ref test results
80
Q

What is sensitivity good for?

A

Ruling out a disease

81
Q

What is specificity good for?

A

Ruling in a disease

82
Q

What could the possible effects of test to the population be?

A
  • Safety
  • Anxiety
  • Accuracy
  • Replicability
83
Q

What is the study design for effectiveness?

A

RCT

84
Q

What is the study design for aetiology?

A

case control, cohort, ecological

85
Q

What is the study design for frequency?

A

Cross-sectional, cohort

86
Q

What is the study design for experience?

A

qualitative study

87
Q

What is the study design for diagnosis?

A

Special cross sectional

88
Q

What are the 5 steps to evidence in clinical practice?

A
  1. Study question- PICO
  2. Find robust evidence in terms of guidelines, clinical evidence, systematic review, primary studies and if not last resort is information from specialists
  3. Appraise the evidence using a tool like CASP or Agree II framework
  4. Is this applicable to your own clinical practice?
  5. Reflect by taking part in audits to assess performance of clinical team against evidenced based measurable data.
89
Q

What is purposive sampling? What study is this usually seen in?

A

Sample chosen based on the characteristics of the population and the objective of the study. Qualitative study.

90
Q

How do you define sensitivity?

A

How accurate a test is in individuals with the disease and the magnitude of false positives.

91
Q

How do you define specificity?

A

How accurate a test is in individuals without the disease and magnitude of false negatives.

92
Q

Where would you search for evidence for quantitative study design?

A

NICE guidelines
Medline- systematic reviews
Primary literature- EMBASE, medline

93
Q

What is cochrane library and embase not good for?

A

Observational and qualitative studies

94
Q

Where would you find qualitative evidence?

A

MEDLINE, EMBASE, Sociological abstracts, Social service abstracts, PscyInfo
Qualitative health research, Social science and medicine

Foundations 3 (8 decks)

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