Number needed to treat (NNT)

The number needed to treat (NNT) or number needed to treat for an additional beneficial outcome (NNTB) is an epidemiological measure used in communicating the effectiveness of a health-care intervention, typically a treatment with medication.

The NNT is the average number of patients who need to be treated to prevent one additional bad outcome.

The ideal NNT is 1, where everyone improves with treatment and no one improves with control. 

A higher NNT indicates that treatment is less effective.

The NNT is an important measure in pharmacoeconomics. 

If a clinical endpoint is severe enough drugs with a high NNT may still be indicated in particular situations. 

NNT is considered when comparing possible side effects of a medication against its benefits. 

With a high NNT, even a small incidence of adverse effects of a drug may outweigh the benefits. 

Information conveyed by the NNT may be incomplete or even contradictory compared to the traditional statistics survival analysis. 

Examples of NNT: naltrexone in reduced heavy drinking is 12 and four complete abstinence is 20. 

Acamprosate has an NNT of 12 for return to any drinking and 9 for reduced drinking. 

Aspirin prevention of cardiovascular disease has an NNT of 50, antibiotics for acute otitis media of 16, 

Antihypertensive medication‘s for prevention of stroke has an NNT of 67 and prevention of death has an NNT of 125, 

Metformin for mortality improvement has an NNT of 14 over 10 years.

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