Table of Contents
risk factor and treatment benefit metrics
see also:
risk of causing an event
absolute risk
absolute risk = (Event rate in those exposed - Event rate in those not exposed)
relative risk
relative risk = (Event rate in those exposed - Event rate in those not exposed) / (Event rate in those NOT exposed)
number needed to harm
number needed to harm = 1 / (Event rate in those exposed - Event rate in those not exposed)
risk ratio
risk ratio = (Event rate in those exposed) / (Event rate in those NOT exposed)
odds ratio
odds ratio = (number events in exposed / number of no event in exposed) / (number events in non-exposed / number of no event in non-exposed)
attributable risk fraction
attributable risk fraction = (Event rate in those exposed - Event rate in those not exposed) / (Event rate in those exposed)
population-attributable fraction (PAF)
PAF combines both the relative risk of an event with respect to a factor, with the prevalence of the factor in the population.
see PAF
risk of REDUCING the likelihood of an event by treatment vs a control
absolute risk reduction
absolute risk reduction = (Event rate in control group - Event rate in treatment group)
relative risk reduction
relative risk reduction = (Event rate in control group - Event rate in treatment group) / (Event rate in control group)
number needed to treat
number needed to treat (NNT) = 1 / (Event rate in control group - Event rate in treatment group)
risk ratio
risk ratio = (Event rate in treatment group) / (Event rate in control group)
odds ratio
odds ratio = (number events in treatment group / number of no event in treatment group) / (number events in control group / number of no event in control group)
preventable fraction among the unexposed
preventable fraction among the unexposed = (Event rate in control group - Event rate in treatment group) / (Event rate in control group)