I am very surprised to hear that a urologist would prescribe a PSA test so fast after surgery. It doesn’t seem feasible that he/she would have thought it would have been at its nadir (low point) after that short period.
PSA is a protein constantly released into the bloodstream by the prostate (or by prostate cancer). Once the primary source of PSA is removed (by surgery, for example), then the measured amount of PSA slowly diminishes in the bloodstream. It has been well documented that the majority of men have a “PSA half-life” of between 2-3 days.
So, let’s do the math. First, it’s possible that the handling of the prostate during surgery causes an additional surge in PSA in the blood…so for a starting value lets use 2x your last tested value (use 5.0 instead of 2.5 ng/mL). Second, let’s assume your PSA diminishes a bit slower than the majority of men…so let’s use a 4-day half-life instead of the 2-3 day norm. Here’s what your doctor should have done, or estimated in his head from experience:
5.0 ng/mL at time of surgery
2.5 ng/mL – 4 days later
1.25 ng/mL – 4 days later, or 8 days after surgery
0.62 ng/mL – 4 days later, or 12 days after surgery
0.31 ng/mL – 4 days later, or 16 days after surgery
You can see how you might still be in the phase of diminishing residual PSA in your bloodstream.
I’ve heard different doctors prescribe different wait periods after surgery before the first PSA test, but most common is 6-weeks (8-weeks is probably the second most common time period I’ve heard). These durations are “rules of thumb” which cover almost all situations (except unusually high PSAs before surgery) plus some margin of error & variation.
I hope this helps.