PSA Doubling Time Calculator

PSA Doubling Time Formula:

\[ T_d = \frac{\ln(2)}{\left(\frac{\ln(PSA_2 / PSA_1)}{(t_2 - t_1)}\right)} \]

Initial PSA (PSA1):

ng/mL

Current PSA (PSA2):

ng/mL

Initial Time (t1):

months

Current Time (t2):

months

PSA Doubling Time (Td):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is PSA Doubling Time?

PSA doubling time (PSADT) is the time it takes for the prostate-specific antigen (PSA) level to double in value. It's an important prognostic marker in prostate cancer management, helping to assess disease aggressiveness and guide treatment decisions.

2. How Does the Calculator Work?

The calculator uses the following formula:

\[ T_d = \frac{\ln(2)}{\left(\frac{\ln(PSA_2 / PSA_1)}{(t_2 - t_1)}\right)} \]

Where:

\( T_d \) — PSA doubling time (months)
\( PSA_1 \) — 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

Explanation: The formula calculates the exponential growth rate of PSA and determines how long it would take to double at that rate.

3. Clinical Significance

Details: Shorter PSADT (<3 months) suggests aggressive disease, while longer PSADT (>12 months) indicates slower progression. It's particularly useful in monitoring patients after radical prostatectomy or radiation therapy.

4. Using the Calculator

Tips: Enter PSA values in ng/mL and time points in months. Ensure PSA2 > PSA1 and t2 > t1 for valid calculation. For best results, use PSA values measured with the same assay method.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal PSA doubling time?
A: There's no "normal" PSADT as it's used for monitoring progression. In prostate cancer, <3 months is considered rapid, 3-12 months intermediate, and >12 months slow.

Q2: How many PSA values are needed for accurate calculation?
A: While two values can give a calculation, more data points over time provide a more reliable trend. Clinical decisions should be based on multiple measurements.

Q3: Does PSA doubling time differ after treatment?
A: Yes, PSADT typically increases (slows) with successful treatment and decreases (accelerates) with disease progression or recurrence.

Q4: Can PSADT be used for screening?
A: No, PSADT is primarily used for monitoring known prostate cancer cases, not for initial screening or diagnosis.

Q5: What factors can affect PSA doubling time?
A: Factors include prostate manipulation (biopsy, DRE), urinary tract infection, prostatitis, and certain medications (5-alpha reductase inhibitors).