1. What is PSA Doubling Rate?

The PSA doubling rate measures how quickly a man's PSA level is rising over time. It's calculated using the natural logarithm of the ratio between two PSA values divided by the time interval between measurements.

2. How Does the Calculator Work?

The calculator uses the following formula:

Where:

• \( PSA_1 \) — Initial PSA value (ng/mL)
• \( PSA_2 \) — Current PSA value (ng/mL)
• \( t_1 \) — Time of initial PSA measurement (months)
• \( t_2 \) — Time of current PSA measurement (months)
• \( \ln \) — Natural logarithm function

Explanation: The formula calculates the exponential growth rate of PSA over time. The doubling time is then calculated as \( \ln(2) \) divided by the rate.

3. Clinical Importance

Details: PSA doubling time is an important prognostic factor in prostate cancer. Faster doubling times (shorter than 3 months) may indicate more aggressive disease.

4. Using the Calculator

Tips: Enter PSA values in ng/mL and time points in months. Ensure time between measurements is sufficient (typically 3-6 months) for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is a concerning PSA doubling rate?
A: Rates >0.35/month (doubling time <2 months) are typically concerning and may warrant further evaluation.

Q2: How many PSA values are needed?
A: While two points give an initial estimate, more measurements over time provide a more reliable trend.

Q3: Does PSA doubling rate diagnose cancer?
A: No, it's one factor among many. Biopsy remains the diagnostic standard for prostate cancer.

Q4: Can medications affect the calculation?
A: Yes, 5-alpha reductase inhibitors (like finasteride) can lower PSA and affect interpretation.

Q5: What if my PSA decreased?
A: The calculation only applies when PSA is rising. Decreasing PSA would give a negative rate.