1. What is Number Needed to Treat (NNT)?

Definition: NNT is the number of patients who need to be treated to prevent one additional bad outcome.

Purpose: It helps healthcare professionals understand the effectiveness of a treatment by quantifying how many people need to receive it to benefit one person.

2. How Does the NNT Calculator Work?

The calculator uses the formula:

Where:

• \( NNT \) — Number needed to treat (dimensionless)
• \( ARR \) — Absolute risk reduction (dimensionless)

Explanation: The smaller the NNT, the more effective the treatment. An NNT of 1 means every patient treated benefits.

3. Importance of NNT in Medicine

Details: NNT helps clinicians and patients make informed decisions about treatments by providing a tangible measure of treatment effectiveness.

4. Using the Calculator

Tips: Enter the Absolute Risk Reduction (ARR) as a decimal between 0 and 1. For example, 0.1 for 10% ARR.

5. Frequently Asked Questions (FAQ)

Q1: What is a good NNT value?
A: Lower NNTs are better. NNT of 2-5 is excellent, while NNT >50 may not be clinically meaningful.

Q2: How is ARR calculated?
A: ARR = Control event rate - Experimental event rate.

Q3: What's the difference between NNT and NNH?
A: NNH (Number Needed to Harm) measures how many need treatment for one to experience harm.

Q4: Can NNT be less than 1?
A: No, NNT values below 1 are not meaningful in clinical practice.

Q5: How precise should NNT be reported?
A: Typically rounded to the nearest whole number for clinical interpretation.