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
1st row in cohort studies
Disease develops, No disease
26
2nd row in cohort studies
Exposed cohort, A, B, A+B
27
3rd row in cohort studies
Non exposed, C, D, C+D
28
4th row in cohort studies
Total, A+C, B+D, A+B+C+D
29
Absolute risk of disease in exposed
A/A+B
30
Absolute risk of disease in non-exposed
C/C+D
31
Odds of finding disease among exposed
A/B
32
Odds of finding disease in non-exposed
C/D
33
Odds ratio for cohort studies
AD/BC I.e. same as that for case-control studies
34
What is the risk difference?
Difference between two absolute risks (exposed and non-exposed)
35
Formula for risk difference
Absolute risk in exposed group - absolute risk in non-exposed group
36
Another name for risk difference?
Absolute risk reduction Attributable risk
37
Calculation of Relative risk
[A/(A+B)] / [C(C+D)]
38
What is the relative risk?
Ratio between the probability of developing the disease if exposed to the probability of developing the disease if not exposed
39
Another name for relative risk
Risk ratio
40
Calculation of population attributable risk (PAR)?
Absolute risk reduction x proportion exposed
41
What does PAR tell us?
Number of cases that could be eliminated by eradicating the exposure
42
What is the rare disease assumption?
When the probability of an event is low (<5% prevalence), odds ratio will = relative risk
43
What happens to odds ratio as prevalence increases?
Odds ratio increases
44
When are odds ratio used?
Case control studies Cohort studies Analysis of dichotomous outcomes in clinical trials
45
Range of values of probabilities
0-1
46
Range of values of absolute risk
0-1 0 = no one in group has disease 1 = everyone in group has disease
47
Range of values of attributable risk
-1 to +1 -1 = risk greater in non-exposed group
48
Range of values of relative risk
0 to infinity
49
Meaning of value of relative risk
<1 = risk in exposed is less than risk in non-exposed 1 = risks are equal in both groups
50
Range of values for odds ratio
0 to infinity