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#1
12-11-2012
 USMLE Forums Addict Steps History: 1+CK+CS Posts: 106 Threads: 35 Thanked 17 Times in 10 Posts Reputation: 27
Calculating the Number Needed to Treat?

A study is done to determine if ralofexine will decrease the incidence of vertebral fracture in post menopausal women. The result are shown
ralofexine placebo
Number of women in study group 2557 2576
number of vertebral fracture 138 ( 5.4%) 260 ( 10.1%)

based on these result, how many women need to be treated to prevent one verbetral fracture?
A 100/5.4=18.5
B 100/10.1=10
C 100/(10.1+5.4)=6.5
D 100/(10.1-5.4)=21
E 100/(10.1*5.4)=2
 The above post was thanked by: riya_rai84 (12-21-2012)

#2
12-11-2012
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 824 Threads: 66 Thanked 465 Times in 298 Posts Reputation: 475

Number needed to treat = 1/attributable risk

Attributable risk = 260/2576 - 138/2557= 10.1-5.4=4.7

Number needed to treat = 100/4,7=21.3
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#3
12-11-2012
 USMLE Forums Addict Steps History: 1+CK+CS Posts: 106 Threads: 35 Thanked 17 Times in 10 Posts Reputation: 27

I confused with exposure minus non exposure( here exposure mean placebo?
) Thank you (
Quote:
 Originally Posted by MedicalExaminer Number needed to treat = 1/attributable risk Attributable risk = 260/2576 - 138/2557= 10.1-5.4=4.7 Number needed to treat = 100/4,7=21.3

#4
12-11-2012
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 824 Threads: 66 Thanked 465 Times in 298 Posts Reputation: 475

U are welcome

simply subtract smaller unit from larger
__________________
Everything is possible for him who believes (MARK 9:23)
245/247/passed on 1st attempt/223/2mos Obsie /3 US LORS/visa not needed/2008 grad
#5
12-11-2012
 USMLE Forums Veteran Steps History: 1+CK+CS+3 Posts: 205 Threads: 6 Thanked 151 Times in 80 Posts Reputation: 161

Absolute risk reduction= Incidence(in untreated/control)-Incidence(in treated/exposed)
i.e 10.1-5.4

Number needed to treat=100/ARR
100/(10-5.4)=21
 The above post was thanked by: riya_rai84 (12-21-2012)
#6
12-11-2012
 USMLE Forums Master Steps History: Step 1 Only Posts: 864 Threads: 62 Thanked 374 Times in 225 Posts Reputation: 384

d 100/(10.1-5.4)=21
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 Tags Biostatistics-Epidemiology, Step-1-Questions

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