Evaluating Causation Flashcards
Definitive groups in case-control studies
Cases
Controls
1st column in table
Exposed
Non exposed
Total
2nd column
Cases
A
C
A+Cd
3rd column
Controls
B
D
B+D
4th column
A+B
C+D
A+B+C+D
1st row
Cases, Controls
2nd row
Exposed, A, B, A+B
3rd Row
Non exposed, C, D, C+D
4th row
Total, A+C, B+D, A+B+C+D
Case exposure rate
A/A+C
Control exposure rate
B/B+D
Odds of exposure in cases
A/C
Odds of exposure in controls
B/D
What is the odds ratio?
Odds of being exposed if you are a case rather than a control
Calculation for odds ratio?
AD/BC
At what point does odds ratio = relative risk?
If disease is rare i.e. prevalence <5%
Values for odds ratio
0 to infinity
How does one calculate CI from odds ratio
Using log transformations
What can we calculate from cohort studies?
Risk rates
Why can risk not be calculated from case-control studies?
Risk = incidence, which needs a prospective observation