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Number needed to treat

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The number needed to treat (NNT) is a way of summarizing the benefit of an intervention to improve health care.[1][2] The NNT has been proposed to improve quantitative literacy.[1] The calculations are derived from the results of a randomized controlled trial of an intervention.

Two-by-two table for a screening program
Outcome
Present Absent
Experimental (intervention) group Cell A Cell BTotal in experimental group
Control group Cell C Cell DTotal in control group
Total with outcome Total without outcome

Contents

Calculations

Event rates

\mbox{Experimental event rate}=\left (\frac{\mbox{Cell A}}{\mbox{Cell A + Cell B}}\right )
\mbox{Control event rate}=\left (\frac{\mbox{Cell C}}{\mbox{Cell C + Cell D}}\right )

Measures of efficacy

\mbox{Absolute risk reduction} =\left (\mbox{Experimental event rate} - \mbox{Control event rate}\right )
\mbox{Number need to treat}=\left (\frac{100}{\mbox{Absolute risk reduction}}\right )

Example

References

  1. ↑ 1.0 1.1 Laupacis A, Sackett DL, Roberts RS (1988). "An assessment of clinically useful measures of the consequences of treatment". N. Engl. J. Med. 318 (26): 1728–33. PMID 3374545.
  2. ↑ Wen L, Badgett R, Cornell J (2005). "Number needed to treat: a descriptor for weighing therapeutic options". Am J Health Syst Pharm 62 (19): 2031–6. DOI:10.2146/ajhp040558. PMID 16174840.

See also

Retrieved from "http://en.citizendium.org/wiki/Number_needed_to_treat"
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