Evaluating Causation Flashcards

1
Q

Definitive groups in case-control studies

A

Cases
Controls

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2
Q

1st column in table

A

Exposed
Non exposed
Total

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3
Q

2nd column

A

Cases
A
C
A+Cd

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4
Q

3rd column

A

Controls
B
D
B+D

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5
Q

4th column

A

A+B
C+D
A+B+C+D

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6
Q

1st row

A

Cases, Controls

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7
Q

2nd row

A

Exposed, A, B, A+B

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8
Q

3rd Row

A

Non exposed, C, D, C+D

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9
Q

4th row

A

Total, A+C, B+D, A+B+C+D

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10
Q

Case exposure rate

A

A/A+C

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11
Q

Control exposure rate

A

B/B+D

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12
Q

Odds of exposure in cases

A

A/C

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13
Q

Odds of exposure in controls

A

B/D

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14
Q

What is the odds ratio?

A

Odds of being exposed if you are a case rather than a control

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15
Q

Calculation for odds ratio?

A

AD/BC

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16
Q

At what point does odds ratio = relative risk?

A

If disease is rare i.e. prevalence <5%

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17
Q

Values for odds ratio

A

0 to infinity

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18
Q

How does one calculate CI from odds ratio

A

Using log transformations

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19
Q

What can we calculate from cohort studies?

A

Risk rates

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20
Q

Why can risk not be calculated from case-control studies?

A

Risk = incidence, which needs a prospective observation

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21
Q

1st column in cohort studies

A

Exposed cohort
Non exposed
Total

22
Q

2nd column in cohort studies

A

Disease develops
A
C
A+C

23
Q

3rd column in cohort studies

A

No disease
B
D
B+D

24
Q

4th column in cohort studies

A

A+B
C+D
A+B+C+D

25
Q

1st row in cohort studies

A

Disease develops, No disease

26
Q

2nd row in cohort studies

A

Exposed cohort, A, B, A+B

27
Q

3rd row in cohort studies

A

Non exposed, C, D, C+D

28
Q

4th row in cohort studies

A

Total, A+C, B+D, A+B+C+D

29
Q

Absolute risk of disease in exposed

A

A/A+B

30
Q

Absolute risk of disease in non-exposed

A

C/C+D

31
Q

Odds of finding disease among exposed

A

A/B

32
Q

Odds of finding disease in non-exposed

A

C/D

33
Q

Odds ratio for cohort studies

A

AD/BC

I.e. same as that for case-control studies

34
Q

What is the risk difference?

A

Difference between two absolute risks (exposed and non-exposed)

35
Q

Formula for risk difference

A

Absolute risk in exposed group - absolute risk in non-exposed group

36
Q

Another name for risk difference?

A

Absolute risk reduction
Attributable risk

37
Q

Calculation of Relative risk

A

[A/(A+B)] / [C(C+D)]

38
Q

What is the relative risk?

A

Ratio between the probability of developing the disease if exposed to the probability of developing the disease if not exposed

39
Q

Another name for relative risk

A

Risk ratio

40
Q

Calculation of population attributable risk (PAR)?

A

Absolute risk reduction x proportion exposed

41
Q

What does PAR tell us?

A

Number of cases that could be eliminated by eradicating the exposure

42
Q

What is the rare disease assumption?

A

When the probability of an event is low (<5% prevalence), odds ratio will = relative risk

43
Q

What happens to odds ratio as prevalence increases?

A

Odds ratio increases

44
Q

When are odds ratio used?

A

Case control studies
Cohort studies
Analysis of dichotomous outcomes in clinical trials

45
Q

Range of values of probabilities

A

0-1

46
Q

Range of values of absolute risk

A

0-1

0 = no one in group has disease
1 = everyone in group has disease

47
Q

Range of values of attributable risk

A

-1 to +1

-1 = risk greater in non-exposed group

48
Q

Range of values of relative risk

A

0 to infinity

49
Q

Meaning of value of relative risk

A

<1 = risk in exposed is less than risk in non-exposed

1 = risks are equal in both groups

50
Q

Range of values for odds ratio

A

0 to infinity