The PSA Blood Test
Prostate specific antigen (PSA) is a protein made by prostate cells. In healthy men, this protein has a role in the normal functioning of the semen. Both noncancerous and cancerous prostate cells make PSA, and some PSA is excreted into the bloodstream. A PSA test measures the amount of PSA in the blood. It is used as a screening test for prostate cancer because men with prostate cancer usually have high PSA levels.
The use of the PSA test has led to a 75% decrease in the number of men presenting with advanced prostate cancer. Over the past 20 years, PSA testing has led to a 40% reduction in the death rate from prostate cancer in America.
However, a PSA test with high levels does not always mean cancer, and normal PSA levels do not always mean a cancer is not present. High levels of PSA can also indicate an enlarged prostate (BPH) or prostatitis (an infection of the prostate). But combined with the digital rectal exam, PSA remains the best way to detect prostate cancer.
Once prostate cancer has been detected, PSA becomes an important test in helping determine the prognosis for cure and in monitoring the success of cancer treatments.