Question
A clinical trial was conducted with 15225 hypertensive patients allotted in the intervention group (New drug) and control group (Old drug) respectively. Results of the research study are given in the following table. Calculate the absolute risk reduction (ARR) and relative risk (RR):
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Control group (old drug)
|
Intervention group (new drug)
|
|
Developed HT complications
|
1800 |
1620 |
|
Did not develop HT complications
|
13425 |
13605 |
| Total subjects |
15225 |
15225 |
| A. |
ARR = 10% and RR = 0.9
|
| B. |
ARR = 1% and RR = 9
|
| C. |
ARR = 1.2% and RR = 0.9
|
| D. |
ARR = 10% and RR = 9
|
Show Answer
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Correct Answer » C
Explanation
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Ans. C. ARR = 1.2% and RR = 0.9
In the given situation, absolute risk reduction (ARR) is 1% and relative risk (RR) is 0.9.
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Relative Risk (RR)
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Attributable Risk (AR)
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Population Attributable Risk (PAR)
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RR=IExp/INon-Exp
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AR=(IExp-INon-Exp)/IExpX100 |
AR=(Total-INon-exp)/ITotalX100 |
- RR is the ratio of the risk in the exposed divided by the risk in the unexposed.
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- AR indicates the number of cases of a disease among exposed individuals that can be attributed to that exposure
- It is an excess risk or risk difference
- A useful measure of the extent of public health problems caused by an exposure
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PAR indicates the number (or proportion) of cases that would not occur in a population if the factor were eliminated. |
| |
Control group (old drug) |
Intervention group (New drug) |
| Developed HT complications |
1800 |
1620 |
| Did not develop HT complications |
13425 |
13605 |
| Total subjects |
15225 |
15225 |
- IC = Incidence of events (hypertensive complications) in the control group = 1800/15225 = 0.118 = 11.8%
- IT = Incidence of events (hypertensive complications) in the treatment group = 1620/15225 = 0.106 = 10.6%
- Absolute risk reduction (ARR) is also known as risk difference.
- ARR = IC–IT = 11.8 –10.6 = 1.2%
- Relative risk (RR) = IT/IC = 0.106/0.118 = 0.9
