(9) Prostate Disorder
What is PSA velocity?
PSA velocity refers to the change in PSA levels over time. It has been published that a change of PSA of greater than 0.75 ng/ml over an interval of 1 year is worrisome for prostate cancer and merits a prostate biopsy. This change of a 0.75 ng/ml is an absolute value and applies regardless of the baseline PSA value.
Therefore, a change of PSA from 4.0 to 4.8 ng/ml carries the same import as a change of PSA from 8.0 to 8.8 ng/ml. It should be recognized that the concept of PSA velocity was an outgrowth of a retrospective study that measured PSA levels in the stored blood samples of men who had been followed over a period of years.
The PSA values of the stored samples were run several times, and averages were calculated; therefore, it is not totally valid to use a single PSA value taken in year 2 and compare its change with a single PSA value from year 1, as is usually done in clinical practice. In addition, there are differences in the PSA assays that are used in different hospitals and laboratories that make comparison of PSA values obtained at different institutions unwieldy in calculating PSA velocity.
PSA velocity - the change in the PSA level over time.