Evidence based medicine

Question 1

Odds ratio

Answer 1

Measure of clinical significance
Ratio between the odds of an event in the treatment group v odds in control group
If odds >1 this means there is increased chance of stated outcome occurring in the treatment group
If odds ratio <1 then reduced likelihood of outcome in treatment group

Question 2

Relative risk

Answer 2

Ratio of risks of the treatment group and control group
RR >1 means there is increased likelihood of stated outcome occurring in the treatment group
RR <1 means there is reduced likelihood of of stated outcome occurring in the treatment group

Question 3

Absolute risk reduction

Answer 3

The difference between the risk of an event in the control group and the risk of the event in the treatment group
i.e. the proportion of patients who are spared the adverse outcome as a result of having received the experimental rather than the control therapy.

e.g ligation reduced the risk of death by 16% compared with control group

Question 4

Number needed to treat

Answer 4

the number of people need to treat to prevent 1 person from experiencing the event

Question 5

Confidence interval

Answer 5

of values around the estimated effect that has a high probability of containing the true value
Bigger sample size = smaller CI
If CI contains 1, then not statistically significant

Question 6

p value