(New page: {{StatsPsy}} In epidemiology, the '''absolute risk reduction''' is the decrease in risk of a given activity or treatment in relation to a control activity or treatment. It is the ...)
In [[epidemiology]], the '''absolute risk reduction''' is the decrease in [[risk]] of a given activity or treatment in relation to a control activity or treatment. It is the inverse of the [[number needed to treat]].<ref>Laupacis A, Sackett DL, Roberts RS. An assessment of clinically useful measures of the consequences of treatment. ''N Engl J Med'' 1988;318:1728-33. PMID 3374545.</ref>
In [[epidemiology]], the '''absolute risk reduction''' is the decrease in [[risk]] of a given activity or treatment in relation to a control activity or treatment. It is the inverse of the [[number needed to treat]].<ref>Laupacis A, Sackett DL, Roberts RS. An assessment of clinically useful measures of the consequences of treatment. ''N Engl J Med'' 1988;318:1728-33. PMID 3374545.</ref>
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For example, consider a hypothetical drug which reduces the relative risk of [[colon cancer]] by 50%. Even without the drug, colon cancer is fairly rare, maybe 1 in 3,000 in every 5 year period. The rate of colon cancer for a 5-year treatment with the drug is therefore 1/6,000, as by treating 6,000 people with the drug, one can expect to reduce the number of colon cancer cases from 2 to 1.
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For example, consider a hypothetical drug which reduces the relative risk of colon cancer by 50%. Even without the drug, colon cancer is fairly rare, maybe 1 in 3,000 in every 5 year period. The rate of colon cancer for a 5-year treatment with the drug is therefore 1/6,000, as by treating 6,000 people with the drug, one can expect to reduce the number of colon cancer cases from 2 to 1.
In general, absolute risk reduction is usually computed with respect to two treatments ''A'' and ''B'', with ''A'' typically a drug and ''B'' a [[placebo]] (in our example above, ''A'' is a 5-year treatment with the hypothetical drug, and ''B'' is treatment with placebo, i.e. no treatment). A defined endpoint has to be specified (in our example: the appearance of colon cancer in the 5 year period). If the [[probability|probabilities]] ''p<sub>A</sub>'' and ''p<sub>B</sub>'' of this endpoint under treatments ''A'' and ''B'', respectively, are known, then the absolute risk reduction is computed as (''p<sub>B</sub>'' - ''p<sub>A</sub>'').
In general, absolute risk reduction is usually computed with respect to two treatments ''A'' and ''B'', with ''A'' typically a drug and ''B'' a [[placebo]] (in our example above, ''A'' is a 5-year treatment with the hypothetical drug, and ''B'' is treatment with placebo, i.e. no treatment). A defined endpoint has to be specified (in our example: the appearance of colon cancer in the 5 year period). If the [[probability|probabilities]] ''p<sub>A</sub>'' and ''p<sub>B</sub>'' of this endpoint under treatments ''A'' and ''B'', respectively, are known, then the absolute risk reduction is computed as (''p<sub>B</sub>'' - ''p<sub>A</sub>'').
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In epidemiology, the absolute risk reduction is the decrease in risk of a given activity or treatment in relation to a control activity or treatment. It is the inverse of the number needed to treat.[1]
For example, consider a hypothetical drug which reduces the relative risk of colon cancer by 50%. Even without the drug, colon cancer is fairly rare, maybe 1 in 3,000 in every 5 year period. The rate of colon cancer for a 5-year treatment with the drug is therefore 1/6,000, as by treating 6,000 people with the drug, one can expect to reduce the number of colon cancer cases from 2 to 1.
In general, absolute risk reduction is usually computed with respect to two treatments A and B, with A typically a drug and B a placebo (in our example above, A is a 5-year treatment with the hypothetical drug, and B is treatment with placebo, i.e. no treatment). A defined endpoint has to be specified (in our example: the appearance of colon cancer in the 5 year period). If the probabilitiespA and pB of this endpoint under treatments A and B, respectively, are known, then the absolute risk reduction is computed as (pB - pA).
The inverse of the absolute risk reduction, NNT, is an important measure in pharmacoeconomics. If a clinical endpoint is devastating enough (e.g.death, heart attack), drugs with a low absolute risk reduction may still be indicated in particular situations. If the endpoint is minor, health insurers may decline to reimburse drugs with a low absolute risk reduction.
↑Laupacis A, Sackett DL, Roberts RS. An assessment of clinically useful measures of the consequences of treatment. N Engl J Med 1988;318:1728-33. PMID 3374545.
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