biostat - sjsmmd

[ArchivalUser]

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

[ArchivalUser]

d.

[ArchivalUser]

samomcos@, may i have some explanations plz

[ArchivalUser]

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)

[ArchivalUser]

@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

[ArchivalUser]

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.

[ArchivalUser]

it's like an absolute eosinophil count versus a percentage of eosinophils in all the leukocytes.

[ArchivalUser]

thank you very much for your explanation

what about Attributable Risk Percent (ARP) ??

[ArchivalUser]

hmm...not so sure about that axiom...

This is what i found ARP =
(incidence in exposed - incidence in unexposed) * 100 / (incidence in exposed )

i guess this is usually used for diseases developed while being exposed to a prticular risk factor.... dunno if it can be applied to this situation.

If a certain drug was found to be more harmful (causing more MIs) than regular therapy or placebo, we could use the ARP for the new drug.


chk this out: http://www.medepi.net/meta/lectures/An_O...2_2003.pdf

[ArchivalUser]

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.