Prostate Cancer Screening Psa Blood Test

The prostate specific antigen test (or PSA test) is a diagnostic blood test often used to screen for prostate cancer. PSA is an enzyme that prevents semen from solidifying. High levels of prostate specific antigen enzyme in the bloodstream have been linked to cancer, but they have also been linked to other disorders of the prostate.

Who Needs Screening?

Who qualifies for the PSA evaluation is a matter of some debate. Younger men may benefit, because early stage tumors are easier to treat. Some medical groups advocate PSA testing for all men over fifty. Men in high risk groups, such as African Americans and men with family histories of prostatic cancer, are sometimes recommended to take the blood test as early as age forty.

PSA Normal Testing LevelsPSA Test Results

Prostate specific antigens are naturally present in the bloodstream in small amounts, and levels tend to rise with age. Compared to Caucasians, Japanese men tend to have lower levels, and African Americans generally have higher levels. So both age and ethnicity have to be taken into account when reading PSA levels.

Although considered to be a diagnostic blood test, levels of PSA do not actually confirm the presence of malignant tumors. In addition to cancer, high PSA levels may be traced to infections, benign prostatic hyperplasia, or inflammation of the gland. Some men have naturally high blood levels of the enzyme and perfectly healthy prostates. High levels of PSA indicate cancer in about a third of all cases.

Cancer Monitoring

While the debate rages on about the validity of PSA as a diagnostic blood test, no one dismisses its use in monitoring cancer treatment. The level of the enzyme in the blood provides urologists with a way of determining if the prostate is responding to treatment or not.

The Debate Over Prostate Specific Antigen Testing

Not everyone in the medical profession believes prostate specific antigen levels are useful as a screening tool. Advocates point out that enzyme screening detects early stage carcinomas eighty percent of the time, and that deaths from prostate cancer have dropped since 1986, when the FDA approved the procedure.

Opponents are not convinced that screening has reduced cancer deaths, and argue that enzyme screening yields “false-positive” results in twenty percent of cases, suggesting malignant growth when none actually exists.

Appropriate ages for screening are also under debate. After age 75 the treatment of prostatic cancer does little, if anything, to lengthen life. PSA opponents consider screening unnecessary after age 75.


American Cancer Society. (2002). Physical exam can find some prostate cancers with normal PSA. Retrieved January 23, 2003 from