1. What is Absolute Risk Reduction (ARR)?

Absolute Risk Reduction (ARR) is the difference in risk between the control group and the experimental group in a clinical trial. It represents the absolute difference in event rates and provides a clear measure of treatment effect.

2. How Does the Calculator Work?

The calculator uses the ARR formula:

Where:

• \( ARR \) — Absolute Risk Reduction (unitless)
• \( CER \) — Control Event Rate (%)
• \( EER \) — Experimental Event Rate (%)

Explanation: ARR measures the absolute difference in event rates between control and experimental groups, providing a straightforward interpretation of treatment benefit.

3. Importance of ARR Calculation

Details: ARR is crucial for understanding the actual clinical benefit of a treatment. It helps clinicians and patients make informed decisions about treatment options and is used to calculate Number Needed to Treat (NNT).

4. Using the Calculator

Tips: Enter both CER and EER as percentages (0-100%). Positive ARR values indicate treatment benefit, while negative values may suggest harm.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between ARR and RRR?
A: ARR shows absolute difference in risk, while RRR (Relative Risk Reduction) shows proportional reduction. ARR is often more clinically meaningful.

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

Q3: What is a clinically significant ARR?
A: Clinical significance depends on the condition and treatment. Generally, larger ARR values indicate greater treatment benefit.

Q4: Can ARR be negative?
A: Yes, negative ARR indicates the experimental treatment may be harmful compared to control.

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 be misleading when baseline risk is low.