1. What is Absolute Risk Reduction?

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:

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

Explanation: ARR measures the actual reduction in risk attributable to the intervention, expressed as an absolute percentage difference.

3. Importance of ARR Calculation

Details: ARR is crucial for understanding the clinical significance of treatment effects, calculating Number Needed to Treat (NNT), and making informed clinical decisions about therapeutic interventions.

4. Using the Calculator

Tips: Enter both CER and EER as percentages (0-100%). Positive ARR values indicate risk reduction, while negative values indicate increased risk in the experimental group.

5. Frequently Asked Questions (FAQ)

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

Q2: How is ARR related to NNT?
A: Number Needed to Treat (NNT) = 1/ARR. It represents the number of patients needed to treat to prevent one additional adverse event.

Q3: When is ARR more useful than RRR?
A: ARR is more clinically meaningful when baseline risks are low, as RRR can overestimate treatment benefits in such scenarios.

Q4: What does a negative ARR mean?
A: A negative ARR indicates that the experimental treatment increases risk compared to the control, which may represent harm or adverse effects.

Q5: How should ARR be interpreted in clinical practice?
A: ARR should be considered alongside confidence intervals, p-values, and clinical relevance to make informed treatment decisions.