Prostate cancer cells appear to produce the protein in elevated quantities and measuring PSA levels allows physicians to detect the presence of cancer when it is microscopic. Elevated or reduced levels of PSA are used for guidelines only. The test is not accurate enough to either completely rule out or confirm the presence of cancer. A number of factors can influence PSA levels. For example, levels determining abnormalities in white males may not be very useful for African American and Asian men.
Age is also a consideration.
PSA levels tend to rise naturally with age, so an elevated level in someone who is 70, for instance, may be less serious than the same level in a younger man. Those using the drug Proscar for treating BPH may have artificially low PSA levels, and cancer might be missed. One study indicated, however, that ejaculation and DREs only raised PSA levels that were already elevated. Most doctors repeat both the digital rectal exam and the PSA test if first results are suspicious before continuing to more invasive tests. While major American urology and cancer organizations advocate annual PSA screening, government and primary care organizations have not embraced this concept.