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Old 12-08-2011
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Stats Absolute Risk Reduction and Number Needed to Treat?

In a study,
100 patients received medication X to prevent the development of diabetes and 200 patients did not receive the medication, 10 patients in the experimental group and 40 patients patients in the control group developed diabetes, what is the absolute risk reduction and number needed to treat?
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Old 12-08-2011
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Quote:
Originally Posted by aknz View Post
In a study,
100 patients received medication X to prevent the development of diabetes and 200 patients did not receive the medication, 10 patients in the experimental group and 40 patients patients in the control group developed diabetes, what is the absolute risk reduction and number needed to treat?
10/100= 0.1
40/200= 0.2
ARR= 0.2-0.1= 0.1
NNT= 1/ 0.1= 10

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Old 12-08-2011
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10% and 10 is the number needed to treat
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Old 12-08-2011
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Default Abste risk reduction

absolute risk reduction = 10/100 - 40/200 = -10/100
I.e. 10 patients for every 100 patients will not have the disease compared to placebo
NNT= 100/10 = 10 patients i.e. Fir every 10 patients receiving the drug 1 will have benefit

Last edited by alaahoda2001; 12-08-2011 at 05:25 PM.
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Old 12-08-2011
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Quote:
Originally Posted by vin31md View Post
10/100= 0.1
40/200= 0.2
ARR= 0.2-0.1= 0.1
NNT= 1/ 0.1= 10

Correct answer.
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Old 07-18-2012
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Thank u guys that was nice discussion.

Can anybody tell me what's the relative risk reduction here? For the same question?
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Old 07-19-2012
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Vin31md: Nicely done but calculation is wrong...the answer should be negative to make sure ur doin it right...
its risk reduction...... -0.1 --> -10% reduction

a/(a+b) / c/(c+d) ---> 0.1 - 0.2 = -0.1
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Old 06-11-2013
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Quote:
Originally Posted by phantom86 View Post
Vin31md: Nicely done but calculation is wrong...the answer should be negative to make sure ur doin it right...
its risk reduction...... -0.1 --> -10% reduction

a/(a+b) / c/(c+d) ---> 0.1 - 0.2 = -0.1

The initial question asked Number Needed To Treat ( NNT ) .
For NNT formula is : NNT= 1/Absolute Risk Reduction = 1/ARR = 1/(c/d)-(a/b) .

For Numbers Needed to Harm
The formula becomes :
NNH = 1/Atributable risk = 1/a/(a+b)-c/(c+ d)
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Old 06-11-2013
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Quote:
Originally Posted by aknz View Post
In a study,
100 patients received medication X to prevent the development of diabetes and 200 patients did not receive the medication, 10 patients in the experimental group and 40 patients patients in the control group developed diabetes, what is the absolute risk reduction and number needed to treat?
NNT= 1/ARR

ARR= Control Event rate - experimental event rate
ARR =40/200-10/100=0.2-0.1=0.1

NNT=1/0.1=10

10 people need to be treated to prevent one diabetes case development
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