1. What is Absolute Risk Difference?

Absolute Risk Difference (ARD) is the difference in event rates between control and experimental groups in clinical studies. It measures the absolute effect size of an intervention.

2. How Does the Calculator Work?

The calculator uses the ARD formula:

Where:

• \( ARD \) — Absolute Risk Difference (fraction)
• \( CER \) — Control Event Rate (fraction)
• \( EER \) — Experimental Event Rate (fraction)

Explanation: ARD represents the absolute change in risk attributable to the intervention, providing a clear measure of clinical significance.

3. Importance of ARD Calculation

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

4. Using the Calculator

Tips: Enter both CER and EER as fractions between 0 and 1. For example, 0.15 represents 15% event rate.

5. Frequently Asked Questions (FAQ)

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

Q2: How is ARD related to NNT?
A: Number Needed to Treat (NNT) = 1/ARD. This indicates how many patients need treatment to prevent one additional event.

Q3: What does a negative ARD mean?
A: Negative ARD indicates the experimental treatment increases risk compared to control, suggesting potential harm.

Q4: When should ARD be used?
A: ARD is particularly useful when the baseline risk is high and absolute benefits need to be communicated clearly to patients.

Q5: What are typical ARD values in clinical studies?
A: ARD values vary widely by condition and intervention, ranging from 0.01 to 0.30 or more, depending on the effectiveness of the treatment.