A PSA test, or prostate specific antigen test, is a blood test commonly used to screen for prostate cancer. Prostate specific antigen is a protein created in the prostate, a walnut sized gland that sits below a man's bladder. A small amount of PSA is common in the blood. Abnormal levels of PSA may indicate a problem with prostate function.
Function
Prostate cancer is the second most common cancer for men after skin cancer, according to MayoClinic.com. A PSA test may help detect prostate cancer early before symptoms develop. Cancerous tissues often produce more prostate specific antigen than health tissues and can help physicians determine whether further testing is needed.
Abnormal Results
While a high PSA level has been linked with prostate cancer, it does not necessarily mean a person has prostate cancer. MedlinePlus, a publication of the National Institutes of Health, explains that a PSA of 4 ng/mL is very high for most men and physicians may opt to do a biopsy of the prostate to determine whether cancerous tissue is present. In men under age 50, 2 ng/mL may be too high. Aside from cancer, an increased level of prostate specific antigen can indicate other prostate conditions such as benign prostatic hypertrophy, an infection of the prostate or a urinary tract infection.
Follow-Up
If a physician determines that a patient's PSA level is abnormally high, a prostate biopsy will often be recommended. A prostate biopsy involves removing a small sample of the prostate tissue and having a lab analyze the sample for cancerous cells. Most often, men with a high PSA level do not have cancer, according to the National Cancer Institute. However, when cancer is present, a physician will recommend that an oncologist evaluate the patient to help stage how far the cancer has progressed and to determine the most appropriate form of treatment.
Screening Recommendations
A physician's recommendations for screenings often vary depending upon each man's risk assessment. Many physicians will recommend yearly screenings starting at age 50 with men at higher risk beginning screenings at age 40 to 45, according to the National Cancer Institute. Several risk factors may increase a man's chances of developing prostate cancer. Physicians often factor in age, race, family history and diet when assessing when a man should have his first prostate specific antigen test.
Limitations
A PSA test cannot tell a physician whether a person has cancer. It is one of many screening tools that physicians use to assess whether further testing is needed, such as a prostate biopsy. A PSA test can help detect small tumors but often may not help a man with rapid growing or aggressive cancer. The National Cancer Institute warns that the testing can also produce false results. False positives occur when the PSA level is elevated but no cancer is present. There is also a chance of a false negative in which the PSA level is within normal range even when prostate cancer is present.
