The reason that PSA must be carefully interpreted in combination with clinical symptoms is that the subsequent testing to follow up on an elevated PSA is costly, surgically invasive, and often met with a high degree of anxiety.
The procedure to biopsy the prostate gland to confirm or rule out a diagnosis of prostate cancer is not without its risks and complications, including injury to adjacent tissues of the bladder and urethra, and may leave moderate to long-term effects of impotence.