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## Number needed to harmThe ## Additional recommended knowledgeNNH is similar to Number needed to treat (NNT), where NNT usually refers to a therapeutic intervention and p of this endpoint are known, then the NNH is computed as 1/(_{non-exposure}p-_{exposure}p).
_{non-exposure}The NNH is an important measure in evidence-based medicine and helps physicians decide whether it is prudent to proceed with a particular treatment which may expose the patient to harms while providing therapeutic benefits. If a clinical endpoint is devastating enough without the drug (e.g. death, heart attack), drugs with a low NNH may still be indicated in particular situations if the number needed to treat, (the converse for side-effects, or the drug's benefit) is less than the NNH. ## Worked ExampleThe following is an example of calculating In a cohort study, individuals with exposure to a risk factor (
^ "Years followed" is a weighted average of the length of time the patients were followed. The incidence with exposure is: The indicence without exposure: To determine the relative risk, divide the incidence with exposure by the incidence without exposure: - relative risk
To determine attributable risk subtract incidence without exposure from incidence with exposure: - .0043 - .0029 = .0014 = .14% = attributable risk
The - =
**Number needed to harm**
This means that if 714 individuals are exposed to the risk factor, 1 will develop the disease that would not have otherwise. |
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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Number_needed_to_harm". A list of authors is available in Wikipedia. |