PSA - Prostate specific antigen, or PSA is a protein present in the bloodstream of those males who have a prostate gland. The PSA level is increased in those who have prostate cancer. Higher levels may also be seen in those with benign prostatic hypertrophy and prostatitis. This test is now widely recognized as a primary screening tool for prostate cancer. The American Cancer Society currently recommends annual testing after the age of 50. The normal range is 0-4ng/ml.