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Old 12-11-2012
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Calculator 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
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Old 12-11-2012
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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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Old 12-11-2012
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Thank for your explanation
I confused with exposure minus non exposure( here exposure mean placebo?
) Thank you (
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Originally Posted by MedicalExaminer View Post
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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U are welcome

simply subtract smaller unit from larger
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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
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d 100/(10.1-5.4)=21
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