1. What is Absolute Risk Reduction?

Absolute Risk Reduction (ARR) is the difference in event rates between control and treatment groups in a clinical trial. It represents the absolute change in risk attributable to the treatment.

2. How Does the Calculator Work?

The calculator uses the ARR formula:

Where:

• Control Rate — Event rate in the control group (0 to 1)
• Treatment Rate — Event rate in the treatment group (0 to 1)

Explanation: ARR shows the actual reduction in risk provided by the treatment compared to control.

3. Importance of ARR Calculation

Details: ARR is crucial for understanding the clinical significance of treatment effects, helping clinicians and patients make informed decisions about therapies.

4. Using the Calculator

Tips: Enter both rates as decimal values between 0 and 1 (e.g., 0.25 for 25%). The control rate should typically be higher than the treatment rate for meaningful interpretation.

5. Frequently Asked Questions (FAQ)

Q1: How does ARR differ from Relative Risk Reduction?
A: ARR shows the absolute difference in risk, while RRR shows the proportional reduction relative to control risk.

Q2: What is a good ARR value?
A: Interpretation depends on context. Generally, higher ARR indicates more effective treatment, but clinical significance depends on the condition and baseline risk.

Q3: When is ARR most useful?
A: ARR is particularly helpful when baseline risks are high, as it shows the actual benefit patients can expect.

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

Q5: How is ARR related to NNT?
A: Number Needed to Treat (NNT) is the reciprocal of ARR (NNT = 1/ARR), showing how many patients need treatment to prevent one adverse event.