PSA Doubling Time
Enter at least two PSA measurements with dates. The calculator fits a linear regression to ln(PSA) versus time to estimate doubling time.
Entry 1
Entry 2
How to Use This Calculator
Collect serial PSA values
Use at least two PSA tests separated by ≥3 months. More points provide a more reliable slope.
Enter dates and PSA concentrations
Ensure PSA is measured in ng/mL. The calculator converts dates to months and fits log-linear regression.
Interpret kinetics with clinical context
Rapid doubling (<6 months) signals aggressive disease and warrants prompt evaluation. Consider imaging and treatment changes accordingly.
Formula
Fit linear regression: ln(PSA) = a + b × time (months).
Doubling time = ln(2) ÷ b
Where b is the slope of natural log PSA over time.
Full Description
PSA doubling time quantifies the velocity of PSA rise, reflecting tumour kinetics in prostate cancer. Short doubling times (≤6 months) predict aggressive behaviour and worse outcomes, guiding escalation to systemic therapy or early imaging. Ensure PSA increases are not due to transient causes (infection, instrumentation) before acting on rapid kinetics. Combine PSADT with absolute PSA level, PSA doubling time trends, imaging, and clinical examination for comprehensive management decisions.
Frequently Asked Questions
How many PSA values are ideal?
Three or more measurements spaced over ≥6 months improve accuracy. The slope becomes unreliable with only two closely spaced values.
Can I mix different laboratories?
Prefer the same assay for consistency. If different labs are used, note potential variability and interpret cautiously.
What if PSA is declining?
A negative slope means PSA is stable or falling. Doubling time is undefined; document stability and continue current management.
Does androgen deprivation therapy affect PSADT?
Yes. Use PSA values after castrate levels are achieved when assessing kinetics in castration-resistant disease.