NNH represents the number of people that need to be treated for one adverse event to ocurr.

- Formula:
**NNH = 1 / ARI** - NNT: number needed to harm
- ARI: absolute risk increase
- ARI = AR: atributabe risk
- Classic USMLE Question:
*"You are asked to analyze survival data after six months of treatment with a drug X. The results are given below:*

Alive Dead

Treated + 10 15

Treated - 10 30

What is the**number needed to harm**for drug X?**Answer**

NNH = 1 / AR

= 1 / (a / a+b) - (c / c+d)

a / a + b = treatment group = 10 / (10 + 15) = 0.40

c / c + d = placebo group = 10 / (10 + 30) = 0.25

NNH = 1 / (0.40 - 0.25) = 1 / 0.15 =**66.6 or 67**

THIS IS WRONG

ReplyDeleteIT SHUD BE 1/(15/25-30/40)=1/0.6-0.75=1/015=6.67

ReplyDeleteNow where's the calculations for NNR ???!! that was my actual reason for being around here..

ReplyDeleteyour reasoning is sound, but shouldn't the answer be 6.66?

ReplyDelete1/0.15=6.667

1/0.15= 6.7 . no? why is 67 the answer?

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