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RC-FoPC2 > 2. Evidence Based Medicine > Flashcards

2. Evidence Based Medicine Flashcards

1
Q

List some of the medical and non-medical factors which may influence an individual’s desire to seek medical attention

A

Medical factors:

  • Ideas, concerns and expectations
  • Iceberg of illness; only see a limited amount of what’s going on - a large volume which doesn’t reach the surface

Non-medical factors:

  • cultural
  • ethnic
  • social
  • economic
  • crisis
  • peer pressure
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2
Q

What is the relevance of EBM in primary care?

A

EBM is the use of mathematical estimates of the risk of benefit and harm, derived from high-quality research on population samples, to inform clinical decision making in the diagnosis, investigation or management of individual patients.

To add value to patients, we must know what the evidence tells us, and what it doesn’t.

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3
Q

Name the three basic principles which constitute EBM

A

EBM is an intersection of

  1. Clinical judgment
  2. Relevant scientific evidence
  3. Patient’s values and preferences
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4
Q

Define epidemiology

A

Epidemiology is the study of populations of people, i.e. population-based medicine.

Clinical epidemiology is the science of applying the principles of population based (epidemiological evidence) to the management of individual patients.

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5
Q

Name some examples of how populations can be studied

A

Observation studies - observing populations are often the first in a multi-stage research process - aimed at identifying causality.

Experimental/Intervention studies - intervening with trials - used to t_est a new treatment or intervention_

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6
Q

Name the three observational study designs and state their individual use.

A
  • Cohort study - used for looking at causality
  • Case control study - used for looking at causality
  • Cross-sectional/longitudinal studies - useful for looking at trends.
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7
Q

What are confounding factors?

A

These are factors associated with both the exposure of interest and the outcome of interest

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8
Q

What is bias?

A

Any trend in the collection, analysis, interpretations, publication or review of data that can lead to conclusions that are systematically different from the truth.

c.f. errors which occur randomly. True answers to questions must take bias into account and limit it wherever possible.

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9
Q

Name the 6 types of bias *SPORRD*

A
  • Selection bias - sample does not represent population
  • Publication bias - positive trials more likely to be published
  • Observation bias - subjectively by observer, variance in their decisions
  • Recall bias - patients know which group they are in, and may be more likely to report symptoms
  • Response bias - patients enrolling themselves/self-selecting
  • Detection bias - observations in treatment group pursued more than those in control group
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10
Q

What are confounding factors? e.g. “increased risk of skin cancer (B) in people using sunscreen (A)”

A

This statement doesn’t make sense. A confounder may explain this - it may be that those with greater sun exposure, use more sun screen.

A confounder (sun exposure) is associated with both the exposure of interest (A) and the outcome of interest (B). Sun exposure is the confounder, in this instance.

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11
Q

Define incidence and its importance in relation to disease

A

Incidence is the number of new cases of disease in a population, in a given time period, also known as the recurrence rate.

  • Usually a percentage.
  • It helps us to understand the RISK of a disease.
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12
Q

Define prevalence and its importance in relation to disease

A

Prevalence is the total number of cases of a disease in a population, either in a time period (period prevalence) or at a specific point (point prevalence).

  • It helps us to understand the BURDEN of disease.
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13
Q

What is the incidence rate if 2 people out of a population of 10 are diagnosed with a disease?

A

2/10 = 0.2 = 20% incidence rate

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14
Q

What is the prevalence of a disease if 4 out of 10 in a population are affected?

A

4/10 = 0.4 people affected = 40% prevalence of population

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15
Q

Describe how different disease patterns show variations in their incidence and prevalence

A

1. Influenza = acute infectious illness with high seasonal incidence rate. Most people recover, some die. Though highly incident, it is not prevalent long-term

2. T2DM = chronic disease with new diagnoses spread throughout year - long-term condition. It occurs, and then is prevalent, with people continuing to be affected by it.

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16
Q

List some of the SORTS of data which can give epidemiological pictures of society

A
  • Mortality
  • Hospital & Clinical activity
  • Infectious disease
  • Cancer
  • Accident
  • GP morbidity statistics
  • Labour force surveys
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17
Q

List some of SOURCES of data which can give epidemiological pictures of society

A
  • Health Protection Scotland
  • Public Health Scotland
  • ONS
  • Clinical Practice Research Datalink (CPRD)
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18
Q

What is a cohort study?

A

A cohort of people are studied based on an exposure and followed up, over time, to evaluate an outcome of interest They can be prospective or retrospective

19
Q

What is the mathematical outcome measure in a cohort study?

A

Relative risk

20
Q

List some advantages and disadvantages of a cohort study

A

Advantages:

  • incidence of disease can be calculated in exposed and non-exposed individuals
  • possible to study multiple outcomes
  • bias less of an issue than CC studies

Disadvantages:

  • large pop. needed
  • expensive (due to duration)
  • duration: drop outs
21
Q

What is meant by ‘relative risk’ (RR) ?

A

RR = outcome measure reported in cohort studies

Measure of risk of the outcome of interest in the exposed group, relative to the unexposed group

22
Q

How do you calculate the relative risk?

A

Risk in exposed group/ risk in unexposed group = RR

If RR = 1, it would indicate no difference in effect between the groups.

23
Q

What is a case control study?

A
  • A comparison between individuals with a disease (outcome) of interest (cases) and those without the disease (outcome) of interest (controls).
  • The cases and controls are each assessed to ascertain if they have had exposure to the variable of interest (exposure).
  • Almost always retrospective, except nested cc studies
24
Q

What are some of the advantages and disadvantages of a case control study?

A

Advantages:

  • Smaller sample sizes are generally required, quicker results and cheaper

Disadvantages:

  • More prone to bias (recall bias)
  • Difficult to prove causation
  • Cannot prove incidence
25
Q

What is the ‘Odds Ratio’ (OR)?

A
  • The odds ratio is similar to the relative risk and is the measure of outcome used in CC studies.
  • Defined as the ratio of odds of exposure in those with the outcome to those without the outcome.
26
Q

How is odds ratio (likelihood ratio) calculated

A
  • Odds of exposure in those with the outcome/ odds of exposure in those without the outcome = odds ratio
  • OR of 1 suggests there is no difference in odds of exposure between the two groups
27
Q

What do the following mean: OR >1 OR <1 OR 1.2

A

Remember, OR is the only measure that can be used in CC study.

  • OR >1 = increased odds of association between exposure and outcome.
  • OR <1 = decreased odds of association between exposure and outcome.
    • e.g. OR 1.2 = a 20% increase in the odds of an outcome with a given exposure.
28
Q

What are cross-sectional/longitudinal studies?

A
  • Look at outcome and exposure in a population, or an individual, at a specific point in time - they look at a cross section of society.
  • If a cross sectional study is repeated multiple times in succession = longitudinal study.
    • e.g. telling us about the pattern of CRC in primary care at a specific point in time.
29
Q

Name an advantage and disadvantage of cross-sectional/ longitudinal studies.

A
  • Both are helpful in looking at trends in a population.
  • It is not possible to infer causality from either of these types of study.
30
Q

Name the gold standard intervention trial used for assessing new treatments

A

Randomised controlled Trial (RCT)

31
Q

What is an RCT?

A
  • Group of patients are randomised to receive either the new treatment of an alternative - often a placebo though it may be the usual, standard of care, or other treatment.
  • Provides strong evidence, with little bias.
  • Though time consuming, expensive and ethical considerations are apparent
32
Q

What are the two types of RCTs?

A
  1. Single blind RCT
  2. Double blind RCT
33
Q

What is meta-analysis and systematic review?

A

Systematic review = a review of a clearly formulated question that uses systematic methods to identify, select and critically appraise relevant research, and to collect and analyse data from the studies that are included in the review.

Meta-analysis = the data/statistical part of a systematic review. Pulls together data from individual studies and analyses this. Data presented into a forest plot (blobbogram)

34
Q

Describe the forrest plot:

  1. Central vertical line
  2. Dashed vertical line
  3. Solid shape
  4. Horizontal line
  5. If HL crosses CVL
A
  • A forest plot can use a variety of statistical outcome measures on the X-axis, e.g. RR, OR
    1. The line of no effect
    1. Line of best fit around the studies
    1. Represents size of study
    1. Represents spread of study (95% CI)
    1. Then study is not statistically significant
35
Q

Describe the hierarchy of evidence

A

In order of increasing strength of evidence:

    1. Expert opinion
    1. Case reports
    1. Cohort studies
    1. RCTs
    1. Systematic reviews

Hierarchy of the LIKELY best evidence

36
Q

What is the importance of the hierarchy of evidence for clinicians?

A
  • Short cut for busy clinicians - focussed reading of best evidence.
  • High quality case-control study may be better than a poorly conducted RCT though!
  • Necessary to critically appraise evidence to see if high quality.
37
Q

State

a. the levels of evidence from strongest to weakest

and

b. the grades of recommendation from strongest to weakest based on the above.

A

Levels of evidence: 1 ++, 1 +, 1 -, 2 ++, 2 +, 2 -, 3, 4

Grades of evidence: A (1++, 1+) B C D (3,4) Tick (clinical experience)

38
Q

What is causality?

A
  • Associations in study results may be able to say A is associated with B, this doesn’t meant that A causes B.
  • Correlation does not mean causation.
  • If a study claims causality, then its important to check that the criteria for causality have been met as these criteria (Bradford-Hill) strengthen the case for causality.
39
Q

Name the 9 criteria for causality (don’t have to be present in every study; for a given disease, many different studies may meet some of the criteria) *ACCEPTSS Bradford*

A
  • 1. Analogy - when one causal agent known, standards of evidence are lowered for a second similar agent.
  • 2. Consistency - multiple studies show pattern
  • 3. Coherence
  • 4. Experiment
  • 5. Plausibility
  • 6. Temporality - exposure must precede onset of disease
  • 7. Specificity
  • 8. Strength of association - magnitude & s. significance
  • 9. Biological gradient - dose-response relationship
40
Q

What is quality improvement and what is the role of audit as part of QI?

A
  • QI = improving quality, safety and effectiveness of patient care.
  • A process to drive change.
  • Audit forms part of QI
41
Q

What are the 5 stages in the Clinical audit cycle?

A
    1. Preparing for audit
    1. Selecting criteria and standards
    1. Measure what is happening now and report on it
    1. Make improvements
    1. Sustain improvements and re-audit to see if changes have improved things.
      * e.g. do all patients with asthma have action plans?

​

  • Collecting data and looking at it is not audit, it is part of an audit. Need to re-audit.
42
Q

Concerning audit: what is meant by criteria and standard?

A
  • Criteria = what you are looking at improving, i.e. all HTN pts should be given lifestyle advice.
  • Standard = numerical part of this, i.e. what proportion of patients should achieve this criteria.
43
Q
A

RC-FoPC2 (7 decks)

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