Prostate-specific antigen, or PSA, is a protein produced by cells of the prostate gland. The PSA test measures the level of PSA in a man’s blood. For this test, a blood sample is sent to a laboratory for analysis. The results are usually reported as nanograms of PSA per milliliter (ng/mL) of blood. A PSA blood test can detect prostate cancer early, but it may not save lives. Many prostate cancers grow slowly, so a PSA test may save the lives of some men while causing others to have unnecessary surgeries or radiation treatments, which could cause lifelong problems such as erectile dysfunction or incontinence.
In addition to prostate cancer, a number of benign (not cancerous) conditions can cause a man’s PSA level to rise. The most frequent benign prostate conditions that cause an elevation in PSA level are prostatitis (inflammation of the prostate) and benign prostatic hyperplasia (BPH) (enlargement of the prostate). There is no evidence that prostatitis or BPH leads to prostate cancer, but it is possible for a man to have one or both of these conditions and to develop prostate cancer as well.
Until recently, many doctors and professional organizations encouraged yearly PSA screening for men beginning at age 50. Some organizations recommended that men who are at higher risk of prostate cancer, including African American men and men whose father or brother had prostate cancer, begin screening at age 40 or 45. However, as more has been learned about both the benefits and harms of prostate cancer screening, a number of organizations have begun to caution against routine population screening. Although some organizations continue to recommend PSA screening, there is widespread agreement that any man who is considering getting tested should first be informed in detail about the potential harms and benefits.
There is no specific normal or abnormal level of PSA in the blood. In the past, most doctors considered PSA levels of 4.0 ng/mL and lower as normal. Therefore, if a man had a PSA level above 4.0 ng/mL doctors would often recommend a prostate biopsy to determine whether prostate cancer was present. But so many factors influence PSA that a single test is never enough to diagnose prostate cancer. If you do have high levels of PSA, your doctor may suggest another test to determine if you have cancer.
However, more recent studies have shown that some men with PSA levels below 4.0 ng/mL have prostate cancer and that many men with higher levels do not have prostate cancer ( 1). In addition, various factors can cause a man’s PSA level to fluctuate. For example, a man’s PSA level often rises if he has prostatitis or a urinary tract infection. Prostate biopsies and prostate surgery also increase PSA level. Conversely, some drugs—including finasteride and dutasteride, which are used to treat BPH lower a man’s PSA level. PSA level may also vary somewhat across testing laboratories.
Swelling of the prostate gland, infection, and recent ejaculation, among other things, can elevate PSA levels. These factors, however, have nothing to do with prostate cancer. Benign prostatic hyperplasia, or enlarged prostate, which is one of the most common conditions that affect men as they age, also can raise PSA.
Another complicating factor is that studies to establish the normal range of PSA levels have been conducted primarily in populations of white men. Although expert opinions vary, there is no clear consensus regarding the optimal PSA threshold for recommending a prostate biopsy for men of any racial or ethnic group.
In general, however, the higher a man’s PSA level, the more likely it is that he has prostate cancer. Moreover, a continuous rise in a man’s PSA level over time may also be a sign of prostate cancer.
When used in screening, the PSA test can help detect small tumors that do not cause symptoms. Finding a small tumor, however, may not necessarily reduce a man’s chance of dying from prostate cancer. Some tumors found through PSA testing grow so slowly that they are unlikely to threaten a man’s life. Detecting tumors that are not life threatening is called “over-diagnosis,” and treating these tumors is called “overtreatment.”
Overtreatment exposes men unnecessarily to the potential complications and harmful side effects of treatments for early prostate cancer, including surgery and radiation therapy. The side effects of these treatments include urinary incontinence, problems with bowel function, erectile dysfunction and infection.
In addition, finding cancer early may not help a man who has a fast-growing or aggressive tumor that may have spread to other parts of the body before being detected.
If your PSA is high, your doctor will look at other risk factors to decide if you need additional testing. These risk factors include race (black men are more prone to prostate cancer than white or Hispanic men), age (prostate-cancer risk increases with age), and family medical history (men who have an immediate family member with prostate cancer are at increased risk).
If, however, your prostate-cancer risk is low—if, for example, you have no risk factors and a digital rectal exam reveals no abnormal-feeling areas in your prostate—your doctor may decide to forego a biopsy and instead do another PSA test a few months or so down the road.
