Please explain the problem of checking vs. non checking psa's?

Not useful: Us preventive task force has determined that routine monitoring of healthy males with psa testing is not useful.

Inconclusive: This question requires an extensive response, but the short answer is that psa has never been proven to save lives when used as a screening tool - that is, testing someone who is otherwise not having symptoms nor isn't considered to be at high risk for prostate cancer (no family history, etc). In fact, using this test may even lead to unnecessary tests and medical procedures that aren't helpful.