Intermediate
Technical
IVT
absolute risk reduction
Difference in event rates between treated and untreated groups, expressed as a percentage.
Full Definition
Absolute risk reduction (ARR) quantifies the actual difference in adverse event rates between treatment and control groups in clinical trials. Unlike relative risk reduction, ARR provides the absolute benefit that patients can expect from treatment. For example, if the event rate decreases from 10% to 8% with treatment, the ARR is 2%. ARR is the reciprocal of the number needed to treat and is crucial for informed decision-making in cardiovascular prevention, as it helps patients understand the actual magnitude of benefit they might receive.
Usage
Usage note: Lowercase except when abbreviated; express as percentage or decimal
In Context
- "The absolute risk reduction for major cardiovascular events was 1.5% over five years of statin therapy." — Clinical trial publication
- "Patients often find absolute risk reduction more meaningful than relative risk reduction when making treatment decisions." — Patient communication guide
Also known as
ARR
risk difference
Contrasted with
absolute risk increase
Don't confuse with
relative risk reduction
relative risk