








USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam 

Thread Tools  Search this Thread  Display Modes 
#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 
The above post was thanked by:  
FaithUSMLE (04102013), neha_subh (04102013) 
#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 
The above post was thanked by:  
FaithUSMLE (04102013), neha_subh (04102013) 
#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????
__________________
lets kick some doors open and help each other to reach our destinies To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts. 
#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:
__________________
lets kick some doors open and help each other to reach our destinies To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts. 
#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 
The above post was thanked by:  
neha_subh (04112013) 
#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 ???
__________________
lets kick some doors open and help each other to reach our destinies To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts. 
#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?
__________________
lets kick some doors open and help each other to reach our destinies To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts. Last edited by neha_subh; 04112013 at 01:49 AM. 
#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%
__________________
lets kick some doors open and help each other to reach our destinies To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts. 
The above post was thanked by:  
med_ziva (04112013) 
Tags 
BiostatisticsEpidemiology 
Thread Tools  Search this Thread 
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Number needed to harm  luschka  USMLE Step 1 Forum  3  02202013 09:31 AM 
Number Needed to Treat (NNT)!  tyagee  USMLE Step 2 CK Forum  13  07182012 08:48 AM 
Number Needed To Treat Calculation?  qurat21  USMLE Step 1 Forum  4  12182011 02:58 AM 
Number needed to treat and number needed to harm  kemoo  USMLE Step 2 CK Forum  2  06172011 11:41 PM 
Number Needed to Treat  kalpana  USMLE Step 1 Forum  2  12212009 11:14 AM 
