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In a trial of an antiplatelet therapy in secondary prevention of stroke, the drug was shown to reduce mortality from stroke, from 8% to 4% over 10 years. What is the number needed to treat to prevent a death over 10 years?
A. 4
B. 5
C. 10
D. 25
E. 100
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samomcos@, may i have some explanations plz
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Number needed to treat = 1/ ARD (no. of pts u will need to treat to prevent one adverse event eg. MI/stroke/hospitalization)
Number needed to harm = 1/ ARI (no pf pts u will need to treat to harm one patient)
ARD - absolute risk decrease ( adverse event rate on placebo/std Rx - adverse event rate on new Rx)
ARI - absolute risk increase ( adverse event rate on new Rx - adverse event rate on placebo/std Rx)
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@samomcos
yesterday some of our form members told that
ARD = [Event Rate in Placebo - Event Rate in Treatment/ Event Rate in Placebo]
can you please clearly tell the defination ??
thanks in advance
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that was for 'relative' risk decrease...this is 'absolute'.
dont be confused, by 'absolute' u mean the actual number of reduction
in relative, u're comparing both as a ratio.
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it's like an absolute eosinophil count versus a percentage of eosinophils in all the leukocytes.
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thank you very much for your explanation
what about Attributable Risk Percent (ARP) ??
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Answer: d) 25. The drug reduced the risk of death post stroke by 4% over 10 years. Therefore if 100 people were treated we could expect the prevention of 4 deaths.