Why do they call PSA undetectable when the test detects PSA ? I realize the PSA is low, but there is still PSA present. I find the terminology confusing.
Each manufacturer's test for PSA has a different lower limit of PSA detection. If the actual PSA is less than that that lower limit, it is undetectable by that particular test and indistinguishable from zero, and is reported as <x, where x is the lower detection
limit of that particular test.