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#1




Biostats Question
A trial shows that an antihypertensice med lowers 5yr risk for stroke from 8 per 1000 patients to 6 per 1000 pts, providing Relativ Risk Reduction of 25%. Based on this study, number of pts who must be treated to prevent the stroke is?
A. 4 B. 75 C. 250 D. 500 E. 2000 Plz give explanation and detailed calculations
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#2




N n t= 1/r r r
1/0.25= 4 
#3




Thats not the Right answer
thats exactly what i did too
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#4




nnt= 1/ARR
but how is it applicable here? anyone??
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#5




Would be D , ARD= 0,0080,006=0,002
Then nnt= 1/0,002= 500 
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#7




If 1000 patients are treated to save 2 patients
Then NNT=1000/2=500
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#8




yes the Right answer is D!
v smart step enhancer. thats a good trick but anders , thats the actual way to go about it. thanx!!
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#9




is this stratergy generalizable??
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#10




Its should be ARR not ARD
ARR is absolute risk reduction. ARR is The reduction in risk associated with treatment as compared to placebo Here ARR =8/10006/1000 ARR=.002 NNT=1/ARR =1/.002 =500 Or you can simply do how many u need to treat to save one live i.e 500
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#11




I dont know ,may be ....
It depends on the question ,i also get confused .depends on how the question is worded .if its simple ,then we can use .
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#12




Quote:
And i got to the answer, IMHO It can be genaralized coz if you think about it, NNT is based on the principle of "How many you need to treat to save one life, right?! So if we are given the no. of pt fatalaties / incidents, We can conclude NNT by simple binary method. Lemme know your thoughts! 
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#13




logical thinking

#14




I have been looking for the answer to your question and finally found the answer here
Apparently you can calculate the NNT from incidence rate Kaplan LN CK Psych Page 110 calculate the ratio of incidence of disease, which is already given in this question as 8/1000 and 6/1000 calculate the difference of those ratio, which will be ARR In this case, 8/10006/1000= 2/1000 = ARR NNT= 1/ARR. So, 1/ARR= 1000/2=500 Another way of doing it: Step1) calculate the difference of incidence of disease (one subtraction) 86=2 Step2) divide your own sample size by difference of incidence of disease (from step1) 1000/2=500 Bottomline: If Incidence rate is given in the question then you can calculate NNT directly from it by 1/Incidence rate or 1/the difference of the Incidence rate. Last edited by Novobiocin; 09062012 at 05:21 PM. 
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BiostatisticsEpidemiology, Step2Questions 
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