PSA Test Facts
Prostate specific antigen (PSA) is a specific protein that is released by the prostate into the bloodstream. The prostate manufactures the liquid part of semen that helps transport sperm and also provides it with nutrition. The PSA test measures the amount of PSA in the blood. There are normal expected levels of PSA in the blood; levels might increase in patients with prostate cancer, benign prostatic hypertrophy (a noncancerous enlargement of the prostate), and prostate infection.
- Historically, PSA has been used as a screening test for prostate cancer, but there is controversy as to whether it is an appropriate blood test to offer male patients. The question that has been asked is whether the benefits of detecting prostate cancers are countered by the complications that might develop due to treatment of a cancer that will not ultimately affect the patient.
- The anecdote is that all men will develop prostate cancer if they live long enough. For that reason, in 2012, the United States Preventive Services Task Force (USPSTF) recommended against routine PSA screening for prostate cancer, referring to studies that showed that the screening did not decrease the death rate from the disease. An elevated PSA test result may also lead to unnecessary operations including prostate biopsies (tissue samples looking for cancer) and prostatectomy (removal of the prostate). Complications of the procedures included urinary incontinence and sexual impotence.
- The American Urologic Association (AUA) has an alternative opinion. Urologists are the specialists who care for prostate cancer patients. They point out that prior to PSA testing, most prostate cancer was metastatic or had spread to other parts of the body at the time of diagnosis. After PSA screening began, prostate cancer was found much earlier before it had a chance to spread.
- The American Cancer Society believes that the patient and health care professional should have an informed discussion of the risks and benefits of performing a PSA screening test and come to a shared decision.
What Is the PSA Test For?
The decision to screen a patient for prostate cancer using PSA should be based upon the patient's individual situation, including age, past medical history, estimated life expectancy, family history of disease, and physical examination. The health care professional and patient should discuss the risks and benefits of the screening test and proceed once they come to an agreement.
For patients who have had prostatectomy (prostate + ectomy = removal) as treatment for cancer, serial PSA measurements may be used to screen for recurrence of the cancer. Serial PSA testing also occurs for patients who have undergone radiation therapy instead of surgery.
What Are the Risk Factors For Prostate Cancer?
There are several factors that increase the risk of developing prostate cancer:
- Age: Prostate cancer increases with age after age 50, and the majority of cancers are diagnosed after the age of 65.
- Ethnicity: African American males are at higher risk for developing and dying from prostate cancer. Asian and Hispanic males are at a decreased risk.
- Family history: A positive family history increases the risk of developing prostate cancer.
- Genetics: There are some gene mutations that increase the risk of prostate cancer, including the BRCA1 and BRCA2 mutations. These are the same genes that increase the risk of breast and ovarian cancers in women.
- Diet: Diets high in red meat and lower in fruits and vegetables may increase cancer risk.
- Location: Prostate cancer is found more frequently in North America, the Caribbean, Australia, and parts of Western Europe, as compared to the rest of the world.
Prostate Cancer Screening Guidelines by Age
In 2013, the American Urologic Association published guidelines for the early detection of prostate cancer.
- Age less than 40: No routine screening in men younger than age 40.
- Age between 40 and 54: No routine screening in men between the ages 40 to 54 years who are at average risk.
- Age between 55 and 69: "The decision to undergo PSA screening involves weighing the benefits of preventing prostate cancer mortality in one man for every 1,000 men screened over a decade against the known potential harms associated with screening and treatment. For this reason, the Panel strongly recommends shared decision-making for men age 55 to 69 years that are considering PSA screening, and proceeding based on men's values and preferences." And screening may be preferred every 2 years instead of annually in patients involved in shared decision-making.
- Age 70 and older: Routine PSA screening is not recommended in men aged 70 years or older or in any man with less than a 10- to 15-year life expectancy.
What Is the Preparation For a PSA Test?
- The PSA test does not need any special preparation, including fasting or dietary preparation.
- Blood is drawn and a laboratory analyzer machine processes the blood sample and reports the result.
What Do PSA Test Results Mean?
- PSA test results are typically reported as nanograms of PSA per milliliter (ng/mL) of blood.
- There is no specific normal or abnormal PSA level in the blood.
- In the past, a level of 4.0 ng/mL was considered as the upper limit of normal, but a patient with a normal PSA may still have cancer, and elevated PSA levels can be produced by a normal prostate gland.
PSA Test Interpretation and Accuracy
PSA levels may be elevated in the presence of a prostate infection (prostatitis) or because of benign prostatic hypertrophy (BPH). However, the higher the PSA level, the more likely that prostate cancer might be present. As well, when serial PSA tests are done over time, a rising PSA level is concerning for the presence of cancer.
An elevated PSA usually leads to a recommendation by the health care professional to consider further testing. These may include an ultrasound of the prostate, cystoscopy (in which a scope is passed through the urethra in the penis to view the urethra and bladder), and urinalysis to look for infection.
A biopsy of the prostate may also be considered, in which a urologist places a thin needle into the prostate and obtains a tissue sample that is examined by a pathologist under a microscope, looking for abnormal or cancerous cells.
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Carter, H. B., et al. "Early Detection of Prostate Cancer: AUA Guideline." The Journal of Urology. 190.2 (2013): 419-426.