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MD3001resp > the science of EBM > Flashcards

the science of EBM Flashcards

1
Q

what are the different types of observational study?

A
  • case control
  • cohort
  • cross sectional
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2
Q

what are examples of experimental studies?

A
  • randomised and non randomised trials
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3
Q

what are the principle of evidence based medicine?

A

1) patient dilema
2) ask
3) acquire
4) appraise
5) apply
6) act and asses.

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4
Q

what are examples of reviews?

A
  • expert opinion
  • systemic review
  • meta-analysis
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5
Q

what are the 8 levels of evidence?

A
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6
Q

what are 5 factors that might decrease the quality of evidence?

A
  • study limitations
  • inconsistency of results
  • indirectness of evidence
  • imprecision
  • publication bias
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7
Q

what are 3 factors that might increase the quality of evidence?

A
  • large magnitude of effect
  • plausible confounding, which would reduce a demonstrated effect
  • dose response gradient
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8
Q

what are the advantages of case studies?

A
  • quick and cheap to conduct
  • rapid publication
  • early indications of problems
  • can help detect new drug side effects and potential uses
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9
Q

what are the 4 disadvantages of case studies?

A
  • statistically weak
  • no control group
  • vert small numbers of patients
  • cases may not be generalised to the wider population
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10
Q

wha are the advantages of cross sectional survey?

A
  • cheap and simple
  • ethically safe
  • useful for planning purposes
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11
Q

what are the disadvantages of cross sectional study?

A
  • cause and effect?
  • volunteer bias
  • unequal distribution of confounders
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12
Q

what are 2 complications that may arise in studies?

A

confounders = uncontrolled extraneous variables
- observation, smokers tend to have smaller babies than non smokers

SPURIOUS ASSOCIATION
- it understand harmful to the foetus?
= - initial studies showed that babies exposed to ultrasound has a lower birth weight
- later studies failed to confirm this observation.

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13
Q

how do case control studies work?

A
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14
Q

advantages of case control studies?

A
  • youcan look at multiple rosk factors at once.
  • good for studying rare conditions or diseases with long latent period
  • useful as initial studies to establish an association
  • do not require a long follow up period
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15
Q

disadvantages of case control study?

A
  • retrospective study which relies on patient recall to determine exposure or patient records
  • confounders
  • selection of control group is difficult
  • unlikely to detect rare causes of disease
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16
Q

how does a cohort study work?

A
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17
Q

what are the advantages of cohort study?

A
  • ethically safe
  • subjects can be matched
  • can show cause precess the effect
  • easier and cheaper than a randomised controlled trial
18
Q

what are the disadvantages of cohort study?

A
  • high drop out rate
  • exposure may be linked to hidden confounder
  • blinding is difficult
  • outcome of interest may take a long time to occur
19
Q

how does a randomised controlled trial work?

A
20
Q

how does a double blind method work?

A
21
Q

design modifiers:
single blind?
double blind?
cross over?
placebo controlled?

A
22
Q

design features of clinical research:
parallel group comparison?
paired (matched) comparison?
within subject comparison?

A
23
Q

advantages of randomised controlled trial?

A
  • unbiased distribution of confounders
  • clearly identified populations
  • randomisation helps statistical analysis
  • more likely to be blinded
24
Q

disadvantages of randomised controlled trial?

A
  • expensive
  • volunteer bias
  • ethical issues if treatment group are seen to respond badly or better than expected
25
Q

what are the 5 problems associated with RCT’s?

A
  • impossible = with treatments for very rare disease where the number of patients is too limited
  • unnecessary = when a treatment produces a ‘dramatic’ benefit - imatinib for chronic myeloid leukaemia
  • stopping trials early= interim analysis of trials is now commonly undertaken to assess whether the treatment is showing benefit if the trial can be stopped early
  • resources = the costs of RCT’s are substantial in money, time and energy
  • generalisability = RCT’s are often carried out on specific types of patients for a relativey short period of time.
26
Q

how do you establish cause and effect?

A

1) is the association due to a chance occurrence?

2) is it due to a flaw in the methodology?

3) is it due to another factor which is linked to both the exposure and the outcome

27
Q

what is the Bradford Hill criterion linking smoking to lung cancer?

A
28
Q

what are the advantages and disadvantages of expert (narrative) review?

A

advantages = comprehensive survey , answers a specific question

disadvantages = expert bias

29
Q

what is a systematic review?

A

a systematic review attempts to identify, appraise and synthesise all the empirical evidence that meets pre- specified eligibility criteria to answer a given research question.

  • it is a comprehensive literature search that identifies all similar and relevant studies that satisfy pre-defined:
  • inclusion criteria
  • exclusion criteria
30
Q

how do researchers conduct a systematic review to minimise bias?

A

researchers conducting systemic reviews use explicit methods aimed at minimising bias, in order coproduce more reliable findings that can be used to inform decision making.

31
Q

describe the vitamin C for preventing and treating the common cold study?

A
32
Q

how do you practise EBM?

A
  • craft a clinical question
  • search the medical literature
  • find the study that will best answer the question
  • perform a critical appraisal
  • determine how the results will help you care for your patient
  • evaluate the results in your patient or population
33
Q

how can you identify different trials?

A
34
Q

why are systematic review views as the gold standard?

A

because the avoid/minimise bias

35
Q

what are the advantages of systematic review?

A
  • uses explicit and reproducible methodology
  • many different studies can be compared and contrasted directly with each other to determine the overall findings
  • reduces bias as it takes into account the range of views and findings
  • less costly to review previous studies than to initiate a new study
36
Q

what are the disadvantages of systematic review?

A
  • dependant on screening strategy
  • can be hard to compare results of studies that have completed in very different ways
  • publication bias
  • very time consuming
37
Q

what is met analysis?

A

combine qualitative and quantitive study data from several selected studies to develop a single conclusion that has a greater statistical power.

38
Q

4 stages of meta analysis

A

1) establish statistical significance with studies that have conflicting results

2) develop a more accurate estimate of effect magnitude

3) provide a more complex analysis of harms , safety data and benefits

4) examine subgroups with individual numbers that are not statistically significant

39
Q

advantages of meta analysis

A
  • greater statistical power
  • greater ability to extrapolate to the general population
  • statistical analysis is more objective than narrative analysis
  • more effect to present a combined result.
40
Q

disadvantages of met analysis

A
  • individual studies do not necessarily all use the same methodology
  • heterogeneity of study populations
  • requires advanced statistical techniques
  • very time consuming

MD3001resp (41 decks)

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