I have read from some of you that we should drink plenty of water before a PSA exam. What does this have to do with a PSA reading?
PSA is ng per ml of serum so drinking or not drinking water could impact a very sensitive PSA test.
Dehydration means that serum concentration would be higher -> too high PSA result
Hydration means that serum concentration would be lower -> too low PSA result
But my guess would be that the effect could possibly be seen the 3:rd or 4 decimal if at all?
That's right. The important point is that the natural variation of PSA is hundreds of times more than the minuscule effect that Gemlin described...so, it is of absolutely no practical concern whatsoever.