Reviewing some of my previous notes and collecting more info and getting a couple emails from other PCa survivors, what it appears to basically boil down to is it is up to the Urologist what test with what precision to use based on their chosen balance between what they consider actionable numbers while avoiding causing the patient unnecessary concern/anxiety. On the tests reporting 0.1 and above, the actual precision is probably 0.05 but the Urologist has chosen a non-ultrasensitive test because they feel there's nothing to act on until it reads 0.1 or above. On the < 0.02 the Urologist has chosen an ultrasensitive test as they may want to more closely monitor the trajectory at 0.02 and above and possibly recommend salvage treatment earlier. But I'm guessing the accuracy on that test is 0.005 or 0.004 like spice said. Even it was accurate to 0.001 increments, there's really nothing do act on when the reading is < 0.02 or even 0.03. It starting to look like 0.02 is sort of the modern cutoff as to when you may want to test more frequently to see if it keeps going up.

This is why anyone getting results to three decimals has always perplexed me as to what's the point of that level of precision. There is nothing to act on if PSA is reading 0.016, 0.014, 0.010, 0.005. Even if it's rising. Yet a patient could get anxiety over seeing rising results only to see their 0.016 go back to 0.010 3 months later. All Urologists would say there is no cause of concern, this is still considered undetectable and no change of plans, just keep testing (usually every 3 months the first couple years then every 6 up to year 5, then once a year.)

The definition of biochemical recurrence of 0.2 is WAY outdated based on dozens of studies over the past 15 years showing the ultrasensitive PSA can accurately predict biochemical recurrence at lower levels. It seems as more data is accumulating the statistical consensus is forming that o.o3 almost certainly predicts biochemical recurrence but 18-24 months in advance of when you would hit 0.2.

It sounds like these days for the top Urological Oncologists to possibly recommend testing every 2 months instead of 3 if you hit 0.02 or above to establish the doubling time and/or rule-out that it's just a fluctuation not related to recurrence. I've seen on patient report of his PSA fluctuating between 0.01 to 0.04 and not going above 0.04 but that may be 2 or 3 patients in 100 according to stats from studies that don't have a recurrence once they hit 0.03.

Newer data shows clear advantage of treating before 0.25. At least one patient confirmed their Urologist initiated salvage radiotherapy when PSA had at least three consecutive rising readings of 0.02 or above and reached at least 0.05. This maximizes the chance of killing remaining cancer cells in the prostate bed prior to micrometastases moving farther out when the PSA is higher. Other Urologists may do testing that only goes to 1 decimal and don't recommend any action until you get a reading of 0.2. Frankly I'd get a new Urologist if this is the case as this is thinking based on outdated information in my opinion with the exception of when you factor age in. There's a difference in the decision making when you are 55 like me and when you are 75. In many cases if normal life expectancy is 10 more years or less salvage RT is probably not going going to extend the person's life especially if the PSA is < 0.2 (in my opinion) They will die of something else before prostate cancer. If you have 30 more years life expectancy, you want to initiate salvage treatment as soon as possible in my opinion when the numbers reliably confirm a recurrence. I think a reading of 0.05 with at least 2 consecutive rising readings over 6 months leading up to that might be a good cutoff but this is a matter of opinion.