Blood levels of the prostate-specific antigen increase with age. To reflect this phenomenon, the reference ranges for PSA levels in both healthy men and men at risk of prostate cancer increase with age, according to the Canadian Cancer Society.
The blood level of prostate-specific antigen is a tumor marker, meaning that elevated levels of PSA may be predictive of prostate cancer, according to the National Cancer Institute. High PSA levels alone are not sufficient to diagnose prostate cancer, but rather are used to identify high-risk men for whom further testing would be beneficial. High PSA levels can also be caused by urinary tract infections, prostatitis or other noncancerous conditions.