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#1




Number Needed to Treat versus Number Needed to Harm?
Ive looked for the equations for those.. And found then to be the same!!
=1/absolute risk reduction So whats the difference?!? 
#2




nnt=1/absolute risk reduction
nnh=1\attributable risk 
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#3




Isnt attributable risk the same as absolute risk reduction?



#4




hope this helps
number needed to treat : number of people you need to give experimental treatment to prevent 1% from getting the disease of interest.
Attributable Risk= difference of treated and untreated groups(to medicine) NNT= 1/AR number needed to harm : number of people you need to expose to risk factor in order to cause 1% to acquire the disease of interest. AR= difference of exposed and unexposed (to risk factors) NNH= 1/AR 
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#5




q: no.needed to treat
Quote:
now time to solve the question acording to definition. Q: Eficacy of new lipid lowering drug marketed (fibrates),clinical control trial at 5yrs given below: Treat:with fibratestreat:with placebo MI2035 non MI980965 number needed to treat????
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#6




in my view
Quote:
First to make a table: Drugs MI +  Fibrates 20 980 placebo 35 965 Absolute Risk Reduction = Event rate in group taking placebo Event rate in group taking fibrates ( i.e. number of people in study to be treated by the drug to prevent MI) = 35/35+965  20/20+980 = 35/1000  20/1000 = 1/200 NNT= 1/ ARR = 200 
#7




Quote:
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#8




Quote:
similarly, event rate in fibrates group is the no. of total people who took the fibrates but still had MI . So if we substract these two, we can get the total number of people who are at risk of getting MI if they dont take the fibrates drug (or take placebo in this case). This gives us the absolute risk reduction. And hence number of people we need to treat in order to prevent MI will be 1/ ARR 
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#9




Quote:
event rate with placebo  event rate with treatment: 35/1000  20/1000 0.035  0.02 = 0.015 now 1 / ARR 1/ 0.015 = 66.66% Am i right ???
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#10




for number needed to harm:
First to make a table:  MIno MI exposure 35965 no exposure20  985 now 1/ AR = 35/1000  20 / 1000 1 / AR = 0.035  0.02 1/AR = 1/ 0.015 = 66.66% Am i right?
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#11




MED_ZIVA its uw concept:
event rate with placebo  event rate with treatment: 35/1000  20/1000 0.035  0.02 = 0.015 now 1 / ARR 1/ 0.015 = 66.66%
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BiostatisticsEpidemiology 
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