Absolute risk reduction
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In clinical epidemiology and evidence-based medicine, the absolute risk reduction is a measure that compares the frequency of a clinical outcome in group of patients exposed to a factor compared to a control group of patients.[1] This measure should be contrasted with the relative risk reduction.
Most scientific journal articles fail to report absolute measures which may lead to exaggerated perceptions of results.[2]
Calculations
| Outcome | ||||
|---|---|---|---|---|
| Present | Absent | |||
| Experimental group | Cell A | Cell B | Total in the experimental group | |
| Control group | Cell C | Cell D | Total in the control group | |
| Total with the outcome | Total without the outcome | |||
- Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \mbox{Experimental event rate EER)} =\left (\frac{\mbox{ Cell A}}{\mbox{Total in the }experimental\mbox{ group}}\right )}
- Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \mbox{Control event rate (CER)} =\left (\frac{\mbox{Cell C}}{\mbox{Total in the }control\mbox{ group}}\right)}
- Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \mbox{Absolute risk reduction} =\left (\mbox{CER - EER}\right)}
Confidence intervals
The confidence intervals can be calculated using the method of Daly:[3]
- Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \mbox{Standard error} =\sqrt{\left(R_1 \times\frac{1-R_1}{N_1}\right) + \left(R_2 \times\frac{1-R_2}{N_2}\right)}}
- Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \mbox{Confidence intervals} = \mbox{Absolute risk reduction} \pm 1.96 \times \mbox{Standard error}}
References
- ↑ Barratt A, Wyer PC, Hatala R, et al (2004). "Tips for learners of evidence-based medicine: 1. Relative risk reduction, absolute risk reduction and number needed to treat". CMAJ 171 (4): 353–8. DOI:10.1503/cmaj.1021197. PMID 15313996. Research Blogging.
- ↑ Welch HG et al.Ratio measures in leading medical journals: structured review of accessibility of underlying absolute risks.BMJ. 2006 Dec 16;333(7581):1248. Epub 2006 Oct 23. PMID 17060338
- ↑ Daly LE (1998). "Confidence limits made easy: interval estimation using a substitution method.". Am J Epidemiol 147 (8): 783-90. PMID 9554420.