Quantifyng Risk

Question 1

epidimiology - OR RR

Answer 1

Odds ratio Relative risk

Question 2

epidimiology - RRR AR

Answer 2

Relative risk reduction Attributable risk

Question 3

epidimiology - ARR

Answer 3

Absolute risk reduction

Question 3

Odds ratio used in

Answer 3

Case control studies

Question 4

Odds ratio

Answer 4

Odds that the group with the disease (cases) was exposed to a risk factor divided by odds that the group without disease (controls) was exposed

Question 5

Relative risk typically used in

Answer 5

Cohort studies

Question 6

Odds ratio equation (and explanation)

Answer 6

OR=(a/c)/(b/d)=ad/bc = X

the risk of the disease is X times higher for exposed then non exposed in population

Question 8

Relative risk

Answer 8

Risk of developing disease in the exposed group divided by risk in the unexposed group

Question 9

epidemiology - RR equation

Answer 9

(a/(a+b))/(c/(c+b))

Question 10

if prevelance is low –> RR? OR?

Answer 10

RR=OR

Question 11

Relative risk reduction (RRR)

Answer 11

The proportion risk reduction attributable to the intervention as compared to a control
(how much the risk is reduced by the intervention)

Question 11

Attributable risk (AR)

Answer 11

The difference in risk between exposed and unexposed groups
or,
The proportion of disease that are ATTRIBUTABLE to the exposure

Question 12

Relative risk reduction example

Answer 12

2% of patients who receive a flu shot develop flu
8% of unvaccinated patients develop the flu
RR=0,25
RRR=1-RR=1-0,25=0,75.
Or RRR=(8-2)/8 = 6/8 = 0.75

Question 13

Absolute risk reduction

Answer 13

The difference risk (not the proportion) attributable to the intervention as compared to control)

Question 14

Attributable risk (AR) equation

Answer 14

AR=a/(a+b)-c/(c+d)

Question 15

Number needed to treat (NNT)

Answer 15

Number of patients who need to be to be treated for 1 patient to benefit

Question 16

Absolute risk reduction example

Answer 16

8% placebo flu - 2% vaccine flu = 6% = 0,6

Question 17

Number needed to treat calculation

Answer 17

1/ARR

Question 18

Number needed to harm

Answer 18

Number of patients who need to ge exposed to a risk factor for 1 patient to be harmed

Question 19

Number needed to harm calculation

Answer 19

1/AR

Question 20

Attributable risk example

Answer 20

If risk for lung cancer is 21% in smokers and 1 in nonsmokers, then 20% of the lung cancer risk in smokers is attributed to smoking

Question 20

Relative risk example

Answer 20

21% smokers develop lung ca and 1% of non smoker

RR=21/1 = 21

Question 23

of 200 patients, 50 have lung Ca. Of these, 45 are smokers. Of remaining 150 patients (no Ca) ,60 are smokers –> Odds Ratio

Answer 23

(45/5)/(60/90) = (45x90)/(5x60) = 13.5

The risk of Lung Ca is 13.5 times higher for smokers than in nonsmokers in this population

Question 24

Quantifyng Risk - TABLE

Answer 24

DISEASE
+ -

RISK FATCTOS + a b
(or intervention) - c d