1. What is Absolute Risk Reduction?

Absolute Risk Reduction (ARR) is the difference in event rates between two groups, typically the control group and the treatment group in clinical studies. It represents the absolute difference in risk between exposed and unexposed populations.

2. How Does the Calculator Work?

The calculator uses the Absolute Risk Reduction formula:

Where:

• \( \text{Event Rate Unexposed} \) — Event rate in control/unexposed group (%)
• \( \text{Event Rate Exposed} \) — Event rate in treatment/exposed group (%)

Explanation: ARR measures the actual risk difference between groups, providing a clear understanding of the intervention's absolute effect.

3. Importance of ARR Calculation

Details: ARR is crucial for understanding the clinical significance of study results, calculating Number Needed to Treat (NNT), and making informed treatment decisions in healthcare.

4. Using the Calculator

Tips: Enter event rates as percentages (0-100%). Event Rate Unexposed is typically the control group rate, while Event Rate Exposed is the treatment group rate.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between ARR and RRR?
A: ARR shows absolute difference in risk, while Relative Risk Reduction (RRR) shows the proportional reduction in risk compared to control.

Q2: How is ARR related to NNT?
A: Number Needed to Treat (NNT) = 1/ARR. It represents how many patients need treatment to prevent one additional bad outcome.

Q3: What is a clinically significant ARR?
A: Clinical significance depends on the context - larger ARR values indicate greater treatment benefit, but what's meaningful varies by condition and risk.

Q4: Can ARR be negative?
A: Yes, negative ARR indicates the treatment may be harmful (increased risk in exposed group).

Q5: When should ARR be used instead of RRR?
A: ARR is preferred for clinical decision-making as it provides the actual risk difference, while RRR can sometimes overestimate treatment effects.