PSA is definitivly used for early screening prior to diagnosis [1]. But we might use the word baseline for different things. As PSA is influenced by the patie

PSA is definitivly used for early screening prior to diagnosis [1]. But we might use the word baseline for different things. As PSA is influenced by the patients physiology and activity [1], it can be helpful to understand what the non-cancer baseline/standard PSA value for a specific patient is, this would need to be established by multiple tests over a couple of years. This can help in distinguishing noise from signal later. After surgery the PSA baseline is zero (by definition, the generating organ has been removed). Any value above zero indicates either metastasis in other body parts or a really bad surgeon. After non-surgery primary treatment (radiation, ...) the PSA does not (necessarily) fall to zero, so here one takes the lowest value after treatment (with a grace period) as the baseline. [1] https://www.cancer.org/cancer/prostate-cancer/detection-diagnosis-staging/tests.html https://www.cancer.org/cancer/prostate-cancer/detection-diag...