PSA test, time of day

Quick answer: "No." I was a Director of Clinical and Anatomical Pathology Laboratory for 20 years. The PSA test is not one where you need to be fasting prior to sample collection. It also does not show what is called diurnal variation: it doesn't vary with time, like - say - Cortisol. "However"...it "can" vary with exercise like bike riding and sexual activity. Six different studies were done with bicycle riders ranging from short 15 minute rides to 4-day long race events. Just two of the studies showed that bicycle riders were found to have PSA values that can be between 3-4-fold higher than non-bicycle riders. But again, the other four studies were inconclusive or did not show any differences with non-bicycle riders. Also, PSA levels can remain higher in men for 24 hours after sexual activity to include ejaculation. Someone who enjoys an active sexual life of 4-5 times per week or more, might perpetually show higher levels of PSA. So, if you are having a blood specimen collected for PSA, I would wait 24-48 hours after your last sexual activity/ejaculation before having the specimen collected.

@rlpostrp How would those activities affect a PSA reading, if you no longer have a prostate ? As in a Prostatectomy.

If you are post-prostatectomy, then the activities that I mentioned (bicycle riding and sexual activity) should not affect a PSA level. "Leftover" prostate tissue that was not removed during the prostatectomy ("surgical margins", likely from Extra Prostatic Extension a.k.a. "EPE"), that slowly begins to grow, will be your only source of PSA test value increases, and...very slowly over time, unless your pathology was such that your prostate cancer was deemed an aggressive form, despite your Gleason Score. My Gleason Score was Low Intermediate Risk at 3+4=7 with just 6-10% of cells being "4", but upon post-RP pathology review of my prostate tissue, my cancer was deemed more aggressive with left seminal vesicle invasion, Cribriform glands, EPE, and surgical margins that I mentioned. I went from being what my urologist thought would be a T2 at worst, to being a pT3b with near certainty that my cancer will return "within" five years...it might be this year, next year, two years, etc., but there is no less than a 25% likelihood of it returning. That is the mystery..."where" is it lurking...hanging out...if my prostate, both seminal vesicles, and both vas deferens were removed along with all vasculature that would provide blood supply to any remaining cancer cells. Exasperating...frustrating...and anxiety-ridden. So far, with two post-op PSA levels at 3 months and 6 months, my values have both been < 0.1 ng/ml ("zero"). Being a pT3b feels like I am walking around with a ticking time bomb on my shoulder...waiting...waiting...for it to tap me on the shoulder and say: "I'm baaack, and I'm going to kill you"... BOOM.

There is literature indicating that since PSA synthesis is related to testosterone levels (which has a diurnal rhythm), that PSA might have a diurnal variation as well.
Based on that hypothesis, I always get my PSA tested about the same time of day.

So. What time of day do you have your blood test?

@firespooks Mine usually tested in the morning. There are a number of studies shown variation of PSA in the morning compared to in the afternoon. Here’s one: https://pubmed.ncbi.nlm.nih.gov/31390085/

HI: @rlpostrp

I am exactly in the same boat as yours. 3+4 with only 1 out of 18 cores positive, but my final pathology report was similar to yours: pT3b disease. Both a GPS test before surgery and a Decipher test after surgery confirmed a very aggressive biolgy for my cancer. I will have my first post-surgery PSA next week and will meet with my surgeon the week after. Like you stated, there is no question about recurrence: the only question is where and when. Given that, I expect the main conversation with my surgeon will be: should we do a pre-emptive adjuvant radiation and/or hormone treatment in the coming months, or should we wait for the signs of recurrence and undertake salavage radiation treatment then? That is what I have been thinking about for the past few weeks: weighing the pros and cons of each approach with respect to both cancer containment and quality of life.