Recently I read that the lab you select to do your PSA test should be the one to stick with forever. The reason as I recall is that each lab performs the test differently. So LabCorp results may differ from Quest Diagnostics and others. The Prostate Cancer Foundation says "Should I use the same lab for all my PSA tests?
It’s important to try to always use the same lab for all of your PSA tests because PSA values can fluctuate somewhat from lab to lab. After radiation therapy, doctors need to look for confirmation from multiple tests because PSA can “bounce” or jump up for a short period, and will later return to its low level." This low level in medical terms is referred to as the Nadir or the lowest point. Yes, pause the bike riding and throw away all of your Playboy mags. Be sure to do what Luke was told in Cool Hand Luke "Boy, get your mind right".