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USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam |
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#1
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Ive looked for the equations for those.. And found then to be the same!!
=1/absolute risk reduction So whats the difference?!? |
#2
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nnt=1/absolute risk reduction
nnh=1\attributable risk |
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Faith-USMLE (04-10-2013), neha_subh (04-11-2013) |
#3
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Isnt attributable risk the same as absolute risk reduction?
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#4
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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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Faith-USMLE (04-10-2013), neha_subh (04-11-2013) |
#5
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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 fibrates----------treat:with placebo MI--------------------20-------------------------------35 non MI---------------980-----------------------------965 number needed to treat????
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#6
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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
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#8
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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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neha_subh (04-11-2013) |
#9
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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
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for number needed to harm:
First to make a table: ---------------------- MI-----------------no MI------------ exposure---------- 35------------------965 no exposure--------20 ----------------- 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
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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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med_ziva (04-11-2013) |
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Biostatistics-Epidemiology |
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