The Cardiovascular
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PSA Doubling Time (PSADT)

Exponential-growth doubling time for serial PSA measurements.

PSA Doubling Time (PSADT)
Earlier PSA
ng/mL
Later PSA
ng/mL
Time between measurements
months
Complete the fields above to see the result.

When to use

  • Quantifying the kinetics of a rising PSA after treatment to help gauge aggressiveness of biochemical recurrence.

Formula

PSADT (months) = ln(2) x (time interval) / ln(PSA2 / PSA1), assuming exponential growth between two PSA values.

Pearls and pitfalls

  • Requires at least two reliably rising PSA values; single fluctuations or assay variability can distort short-interval estimates.

References

  1. Pound CR, et al. JAMA. 1999;281(17):1591-1597 (natural history of PSA-only recurrence and doubling time thresholds).