20 Flashcards

1
Q

Types of analytic studies

A
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2
Q

Limitations of cohort studies

A
  • Can be inefficient with rare/slow to develop outcomes
  • Can be inefficient with transient/acute exposures
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3
Q

Alternatives to the limitations of cohort studies

A

Historical cohort studies
Case-control studies

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4
Q

What issues can case-control studies address that cohort studies can’t?

A
  • Designed for rare/slow to develop outcomes
  • Can efficiently examine acute or transient exposures
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5
Q

Cohort studies vs case-control studies

A

COHORT:
Measure exposure status
Follow over time
Compare development of outcome (incidence)

CASE-CONRTOL
Identify people with outcome
Find people without outcome
Compare exposure likelihood beforehand (odds)

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6
Q

Case-control studies diagram

A
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7
Q

Logic of case-control studies

A

Is the exposure more or less likely in people with the outcome (cases) than without (controls)?

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8
Q

Step by step of a CASE CONRTOL study

A
  1. Identifying source population
  2. Identify people with outcome (cases)
  3. Same people without outcome from the same population (controls)
  4. Measure exposure prior to outcome in cases and controls
  5. Compare odds of exposures to calculate measure of association (odds ratio)
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9
Q

In case-control studies what measure of association is used ?

A

Odds ratio

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10
Q

Why is the odds ratio used

A

Can’t calculate incidence of outcome
Have selected number of people in study with and without outcome

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11
Q

Odds are not a measure of ……

A

Occurrence

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12
Q

Odds ratio features

A

Measure of association
- Ratio of odds instead of incidences
- How many times as likely cases are to have the exposure
compared to controls

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13
Q

Interpretation of the odds ratio vs the relative risk

A
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14
Q

WHEN A DISEASE IS RARE…

A

Fortunately… OR ≅ RR
- When disease is rare, OR approximates the RR ( rare disease
assumption)
- Can interpret OR just like RR

Use RR interpretation in this course???? Wtf does that mean?!!!?

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15
Q

Interpreting the odds ratio - 4 key things

A
  • exposed group
  • value
  • outcome
  • comparison group
  • use RR interpitation
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16
Q
  1. Sample people without outcome from same population (controls)
  2. Measure exposure prior to outcome in cases and controls

Controls don’t have outcome so when do you measure exposure for controls?

A
17
Q

Case selection - wtf does any of this mean

A

Usually try to identify incident cases
Sometimes just recruit people with the outcome ( prevalent cases) Case-control studies defined by outcome
So only one per study
Really important clearly defined and readily identifiable

18
Q

Control selection

A

Need to represent the exposure distribution of people without the outcome in the source population

Must be capable of becoming a case

Often select multiple controls per case for statistical power

19
Q

Exposure measurement

A

Exposure measurement must be comparable
- dead cases vs alive controls
- interviewers may act differently for cases and controls
- cases trying to work out what made them sick
- outcome may affect recall ability

20
Q

Case-control studies - approximate____

A

RR with OR (interpret the same way)

21
Q

Cohort vs case-control studies

A
22
Q

Strengths of case-cotrol study

A

Strengths:
- Rare outcomes, transient exposures
- Multiple exposures
- Temporal sequencing
- Often comparatively quick and inexpensive

23
Q

Limitations of case control study

A
  • Usually can only study one outcome
  • Difficult to select appropriate control group
  • Can be susceptible to selection and recall bias
24
Q

RCTS and the hierarchy of evidence

A