How is absolute risk reduction calculated?

Absolute risk reduction (ARR) is a measure used to quantify the effectiveness of a treatment compared to a control group. It is calculated by taking the difference between the baseline risk of an event occurring in the control group and the risk of that event occurring in the treatment group.

The correct approach to ARR involves identifying the absolute risk for both groups—the control group (which typically receives a placebo or standard treatment) and the treatment group (which receives the new intervention). The formula subtracts the absolute risk in the treatment group from the absolute risk in the control group. Therefore, when the treatment reduces the event rate, the ARR indicates how much the treatment decreases the risk compared to the control.

This calculation is crucial in clinical decision-making, as it provides clear insight into how effective a treatment is in reducing the occurrence of an outcome when compared directly to an alternative. It can help clinicians understand the real-world impact of a treatment, guiding them in patient discussions and treatment planning.

Contextually, knowing how to apply this calculation aids healthcare professionals in interpreting study results, particularly when assessing the benefits of new treatments against existing standards of care.