Enter the time interval between the two PSA measurements and the second and first PSA measurements into the calculator to determine the Psa Doubling Time.

## Psa Doubling Time Formula

The following formula is used to calculate the Psa Doubling Time:

DT = (t * log(2)) / log(P2/P1)

Variables:

- DT is the Psa Doubling Time
- t is the time interval between the two PSA measurements
- P2 is the second PSA measurement
- P1 is the first PSA measurement

To calculate the Psa Doubling Time, multiply the time interval between the two PSA measurements by the natural logarithm of 2. Then divide the result by the natural logarithm of the ratio of the second PSA measurement to the first PSA measurement.

## What is a Psa Doubling Time?

PSA Doubling Time refers to the period it takes for the level of Prostate-Specific Antigen (PSA) in a man’s blood to double. PSA is a protein produced by both normal and malignant cells in the prostate gland. The PSA Doubling Time is often used as an indicator of the aggressiveness of prostate cancer and the effectiveness of treatment.

A short PSA Doubling Time (less than three months) is associated with a more aggressive disease and a poorer prognosis, while a longer PSA Doubling Time (more than 12 months) is associated with a less aggressive disease and a better prognosis. It is calculated by measuring the PSA levels at different points in time and using a mathematical formula to determine how long it takes for the PSA level to double.

## How to Calculate Psa Doubling Time?

The following steps outline how to calculate the Psa Doubling Time.

- First, determine the initial PSA level (PSA1).
- Next, determine the final PSA level (PSA2).
- Next, calculate the difference between the final and initial PSA levels (PSA2 – PSA1).
- Finally, divide the difference by the initial PSA level and multiply by the time interval between the two PSA measurements to calculate the Psa Doubling Time.
- After inserting the variables and calculating the result, check your answer with the calculator above.

**Example Problem:**

Use the following variables as an example problem to test your knowledge.

Initial PSA level (PSA1) = 4.5

Final PSA level (PSA2) = 9.2

Time interval between the two PSA measurements = 6 months