Preventable fraction among the unexposed
In epidemiology, preventable fraction among the unexposed (PFu), is the proportion of incidents in the unexposed group that could be prevented by exposure. It is calculated as , where is the incidence in the exposed group, is the incidence in the unexposed group, and is the relative risk.[1][2] It is a synonym of the relative risk reduction.
It is used when an exposure reduces the risk, as opposed to increasing it, in which case its symmetrical notion is attributable fraction among the exposed.
Numerical example
Experimental group (E) | Control group (C) | Total | |
---|---|---|---|
Events (E) | EE = 15 | CE = 100 | 115 |
Non-events (N) | EN = 135 | CN = 150 | 285 |
Total subjects (S) | ES = EE + EN = 150 | CS = CE + CN = 250 | 400 |
Event rate (ER) | EER = EE / ES = 0.1, or 10% | CER = CE / CS = 0.4, or 40% |
Equation | Variable | Abbr. | Value |
---|---|---|---|
CER - EER | absolute risk reduction | ARR | 0.3, or 30% |
(CER - EER) / CER | relative risk reduction | RRR | 0.75, or 75% |
1 / (CER − EER) | number needed to treat | NNT | 3.33 |
EER / CER | risk ratio | RR | 0.25 |
(EE / EN) / (CE / CN) | odds ratio | OR | 0.167 |
(CER - EER) / CER | preventable fraction among the unexposed | PFu | 0.75 |
gollark: Other light sources do scatter. This is why the sun is vaguely yellow and the sky is blue.
gollark: https://xkcd.com/2027
gollark: It seems like both are maybe valid?
gollark: This may take anywhere from 2μs to 10^37 teraseconds.
gollark: Fiiiiiine, I'll go actually check the recognized definition.
See also
- Population Impact Measures
- Preventable fraction for the population
References
- Aschengrau, Ann; Seage, George R. (2014). Essentials of epidemiology in public health (3rd ed.). Burlington, MA: Jones & Bartlett Learning. p. 67. ISBN 9781449657338. OCLC 826123155.
- Rothman, Kenneth J.; Greenland, Sander; Lash, Timothy L. (2012). Modern epidemiology (3rd ed.). Philadelphia: Lippincott Williams & Wilkins. ISBN 9780781755641. OCLC 169455558.
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