There are two PSA tests that are most often used to track for residual cancer after prostate cancer treatment.
The first is the standard PSA test, approved by the FDA in 1994 and sensitive to 0.1 ng/mL. Anything below 0.1 ng/mL is considered undetectable.
The second is the ultrasensitive PSA test. This test is sensitive to 0.01 ng/mL and is considered by some prostate cancer experts to be better at picking up any significant rise in PSA following prostate cancer treatment.
There is controversy about which PSA test to use in tracking prostate cancer patients after treatment. Some urologists believe that anything below 0.1 ng/mL is insignificant so use only the standard PSA test. They say that the ultrasensitive test, with PSA lower limit of 0.01 ng/mL gives too much emphasis to what is essentially 'noise' or test variability,say,the difference between 0.01 and 0.03 ng/mL
When you see individual PSA test results reported on the forum, those with values one number to the right of the decimal point have had the standard PSA test; those with two numbers to the right of the decimal have had the ultrasensitive PSA test.
Example: 0.1 ng/mL vs. 0.01 ng/mL
Age 59 PSA 2.6 PSA velocity quadrupled in 1 yr