@jc76 From my personal PoV, my PSA is undetectable if the test I'm using can't detect it. The regular PSA test makes perfect sense for routine screening and monitoring, because most men who haven't had a prostatectomy or radiation will have (normal, healthy) PSA well above 0.1 anyway, so the extra senisitivity brings no benefit.

For me, on multifaceted treatment for stage 4, I want the earliest possible warning when my mCSPC might be developing castrate resistance. As long as my PSA remains < 0.01 on the ultrasensitive test, my medical team is highly confident there's no _active_ prostate cancer in me, and that helps me feel more secure living day to day. It also helps them interpret scans: for example, with PSA < 0.01, its highly probable that lucency near my spinal surgery site is benign bone remodelling rather than new cancer activity, so we're just keeping a casual eye on it, but not doing any new radiation.

If/when my PSA becomes detectable on the ultrasensitive test, I'll have to deal with it, but I'm enjoying the deep remission right now.

@jc76
I think you have the arrow backwards I think you meant to say < .1 not >.1.

I did say the medical community GENERALLY Considers < .1 As undetectable. I did not say they always consider that. I then followed it up by another message discussing other opinions, where some doctors consider < .03 as undetectable.

I’m not sure what you mean by < .10 Since that’s the same as < .1, though I never do include the zero After the < .1

Mayo does tell people that the undetectable PSA is < .1. They don’t just stop at .1. Other people have talked about it, people that are Mayo patients. One of them said they thought Mayo used < .001, But then they came back and said they were wrong and it was < .1.

And then there’s what AI says about it, They used widely instead of generally

After a radical prostatectomy, a PSA level of less than 0.1 ng/mL is widely considered by major institutions and medical professionals to be undetectable or negligible.

This threshold is a common clinical benchmark, as the goal of the surgery is to remove all prostate tissue, the source of PSA production. Different laboratories may report varying lower limits of detection (e.g., < 0.02 ng/mL or < 0.05 ng/mL using ultrasensitive tests), but for practical clinical purposes, anything below 0.1 ng/mL is generally viewed as an absence of detectable PSA.