Number needed to treat: Difference between revisions
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imported>Robert Badgett |
imported>Robert Badgett |
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===Deriving the NNT from the odds ratio or relative risk ratio=== | ===Deriving the NNT from the odds ratio or relative risk ratio=== | ||
The odds ratio may be used to derive the | The [[odds ratio]] may be used to derive the number needed to treat:<ref name="pmid11914297">{{cite journal |author=Furukawa TA, Guyatt GH, Griffith LE |title=Can we individualize the 'number needed to treat'? An empirical study of summary effect measures in meta-analyses |journal=Int J Epidemiol |volume=31 |issue=1 |pages=72–6 |year=2002 |month=February |pmid=11914297 |doi= |url=http://ije.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=11914297 |issn=}}</ref><ref name="pmid9139558">{{cite journal |author=McQuay HJ, Moore RA |title=Using numerical results from systematic reviews in clinical practice |journal=Ann. Intern. Med. |volume=126 |issue=9 |pages=712–20 |year=1997 |month=May |pmid=9139558 |doi= |url=http://www.annals.org/cgi/content/full/126/9/712 |issn=}}</ref> | ||
:<math>NNT = \frac{1 - CER + OR * CER}{CER * (1-OR)* (1 - CER)} \mbox{, where CER is control event rate and OR is odds ratio}</math> | :<math>NNT = \frac{1 - CER + OR * CER}{CER * (1-OR)* (1 - CER)} \mbox{, where CER is control event rate and OR is odds ratio}</math> | ||
The relative risk ratio may be used to derive the | The [[relative risk ratio]] may be used to derive the number needed to treat:<ref name="pmid11914297">{{cite journal |author=Furukawa TA, Guyatt GH, Griffith LE |title=Can we individualize the 'number needed to treat'? An empirical study of summary effect measures in meta-analyses |journal=Int J Epidemiol |volume=31 |issue=1 |pages=72–6 |year=2002 |month=February |pmid=11914297 |doi= |url=http://ije.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=11914297 |issn=}}</ref><ref name="pmid8601116">{{cite journal |author=Chatellier G, Zapletal E, Lemaitre D, Menard J, Degoulet P |title=The number needed to treat: a clinically useful nomogram in its proper context |journal=BMJ |volume=312 |issue=7028 |pages=426–9 |year=1996 |month=February |pmid=8601116 |pmc=2350093 |doi= |url=http://bmj.com/cgi/pmidlookup?view=long&pmid=8601116 |issn=}}</ref> | ||
:<math>NNT = \frac{1}{CER * (1-RRR)} \mbox{, where CER is control event rate and RRR is relative risk ratio}</math> | :<math>NNT = \frac{1}{CER * (1-RRR)} \mbox{, where CER is control event rate and RRR is relative risk ratio}</math> | ||
The [[relative risk reduction]] may be used to derive the number needed to treat:<ref name="pmid11914297">{{cite journal |author=Furukawa TA, Guyatt GH, Griffith LE |title=Can we individualize the 'number needed to treat'? An empirical study of summary effect measures in meta-analyses |journal=Int J Epidemiol |volume=31 |issue=1 |pages=72–6 |year=2002 |month=February |pmid=11914297 |doi= |url=http://ije.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=11914297 |issn=}}</ref><ref name="pmid8601116">{{cite journal |author=Chatellier G, Zapletal E, Lemaitre D, Menard J, Degoulet P |title=The number needed to treat: a clinically useful nomogram in its proper context |journal=BMJ |volume=312 |issue=7028 |pages=426–9 |year=1996 |month=February |pmid=8601116 |pmc=2350093 |doi= |url=http://bmj.com/cgi/pmidlookup?view=long&pmid=8601116 |issn=}}</ref> | |||
:<math>NNT = \frac{1}{CER * (RRR)} \mbox{, where CER is control event rate and RRR is relative risk reduction}</math> | |||
==Example== | ==Example== | ||
Revision as of 22:46, 1 March 2009
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.
| Outcome | ||||
|---|---|---|---|---|
| Present | Absent | |||
| Experimental (intervention) group | Cell A | Cell B | Total in experimental group | |
| Control group | Cell C | Cell D | Total in control group | |
| Total with outcome | Total without outcome | |||
Calculations
Event rates
Measures of efficacy
Deriving the NNT from the odds ratio or relative risk ratio
The odds ratio may be used to derive the number needed to treat:[3][4]
The relative risk ratio may be used to derive the number needed to treat:[3][5]
The relative risk reduction may be used to derive the number needed to treat:[3][5]
Example
References
- ↑ 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. [e]
- ↑ 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. Research Blogging.
- ↑ 3.0 3.1 3.2 Furukawa TA, Guyatt GH, Griffith LE (February 2002). "Can we individualize the 'number needed to treat'? An empirical study of summary effect measures in meta-analyses". Int J Epidemiol 31 (1): 72–6. PMID 11914297. [e]
- ↑ McQuay HJ, Moore RA (May 1997). "Using numerical results from systematic reviews in clinical practice". Ann. Intern. Med. 126 (9): 712–20. PMID 9139558. [e]
- ↑ 5.0 5.1 Chatellier G, Zapletal E, Lemaitre D, Menard J, Degoulet P (February 1996). "The number needed to treat: a clinically useful nomogram in its proper context". BMJ 312 (7028): 426–9. PMID 8601116. PMC 2350093. [e]